KVM: x86: add per-vCPU exits disable capability

From: Sean Christopherson <[email protected]>

Reject KVM_CAP_X86_DISABLE_EXITS if userspace attempts to disable MWAIT exits and KVM previously reported (via KVM_CHECK_EXTENSION) that MWAIT is not allowed in guest, e.g. because it's not supported or the CPU doesn't have an aways-running APIC timer.

Fixes 4d5422cea3b6 ("KVM: X86: Provide a capability to disable MWAIT intercepts")

Signed-off-by Sean Christopherson <[email protected]>

Co-developed-by Kechen Lu <[email protected]>

Suggested-by Chao Gao <[email protected]>

---
 arch/x86/kvm/x86.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

arch/x86/kvm/x86.c +0 -0

index b419b258ed90..6ec01362a7d8 100644

-----Original Message-----
From: Sean Christopherson <[email protected]>
Sent: Wednesday, July 20, 2022 10:54 AM
To: Kechen Lu <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Somdutta Roy <[email protected]>; linux- [email protected]
Subject: Re: [RFC PATCH v4 3/7] KVM: x86: Reject disabling of MWAIT interception when not allowed

External email: Use caution opening links or attachments

Quoted 4 lines · Kechen Lu

From: Sean Christopherson <[email protected]>

Reject KVM_CAP_X86_DISABLE_EXITS if userspace attempts to disable MWAIT exits and KVM previously reported (via KVM_CHECK_EXTENSION)

that

Quoted 3 lines

MWAIT is not allowed in guest, e.g. because it's not supported or the CPU doesn't have an aways-running APIC timer.

Quoted 4 lines

Fixes 4d5422cea3b6 ("KVM: X86: Provide a capability to disable MWAIT

intercepts")

Signed-off-by Sean Christopherson <[email protected]>

Co-developed-by Kechen Lu <[email protected]>

Needs your SOB.

Quoted 1 line

Suggested-by Chao Gao <[email protected]>

For code review feedback of this nature, adding Suggested-by isn't appropriate.
Suggested-by is for when the idea of the patch itself was suggested by someone, where as Chao's feedback was a purely mechanical change.

arch/x86/kvm/x86.c static inline bool

Quoted 9 lines

---
 arch/x86/kvm/x86.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

arch/x86/kvm/x86.c index renamed from arch/x86/kvm/x86.c +0 -0

b419b258ed90..6ec01362a7d8 100644

arch/x86/kvm/x86.c +0 -0

@@ -4199,6 +4199,16 @@ static inline bool

kvm_can_mwait_in_guest(void)

Quoted 2 lines

arch/x86/kvm/x86.c +0 -0

              boot_cpu_has(X86_FEATURE_ARAT);  }
 

arch/x86/kvm/x86.c static inline bool kvm_can_mwait_in_guest(void) · line 4204

Quoted 3 lines

arch/x86/kvm/x86.c +3 -0

+static u64 kvm_get_allowed_disable_exits(void)
+{
+     u64 r = KVM_X86_DISABLE_VALID_EXITS;

In v3 I "voted" to keep the switch to KVM_X86_DISABLE_VALID_EXITS in the next patch[*], but seeing the result I 100% agree it's better to handle it here since the "enable" patch previously used KVM_X86_DISABLE_VALID_EXITS.

[*] https://lore.kernel.org/all/[email protected]

arch/x86/kvm/x86.c static inline bool kvm_can_mwait_in_guest(void) · line 4206

Quoted 2 lines

arch/x86/kvm/x86.c +2 -0

+
+     if(!kvm_can_mwait_in_guest())

Space after the "if".

arch/x86/kvm/x86.c +2 -0

@@ -5980,6 +5987,8 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event,
 int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			    struct kvm_enable_cap *cap)
 {
+	struct kvm_vcpu *vcpu;
+	unsigned long i;
 	int r;
 
 	if (cap->flags)

arch/x86/kvm/x86.c +9 -2

+			kvm_for_each_vcpu(i, vcpu, kvm) {
+				kvm_ioctl_disable_exits(vcpu->arch, cap->args[0]);
+				kvm_make_request(KVM_REQ_DISABLE_EXITS, vcpu);
+			}
+		}
+		mutex_unlock(&kvm->lock);
 
 		kvm_ioctl_disable_exits(kvm->arch, cap->args[0]);
 
 		r = 0;
-disable_exits_unlock:
-		mutex_unlock(&kvm->lock);
 		break;
 	case KVM_CAP_MSR_PLATFORM_INFO:
 		kvm->arch.guest_can_read_msr_platform_info = cap->args[0];

@@ -10175,6 +10187,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 		if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING, vcpu))
 			static_call(kvm_x86_update_cpu_dirty_logging)(vcpu);
+
+		if (kvm_check_request(KVM_REQ_DISABLE_EXITS, vcpu))
+			static_call(kvm_x86_update_disabled_exits)(vcpu);
 	}
 
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||

Signature · 1 line

2.32.0

-----Original Message-----
From: Sean Christopherson <[email protected]>
Sent: Wednesday, July 20, 2022 11:42 AM
To: Kechen Lu <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Somdutta Roy <[email protected]>; linux- [email protected]
Subject: Re: [RFC PATCH v4 5/7] KVM: x86: add vCPU scoped toggling for disabled exits

External email: Use caution opening links or attachments

Quoted 2 lines · Kechen Lu

(quoted diff) +0 -0

@@ -5980,6 +5987,8 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm,

struct kvm_irq_level *irq_event, int kvm_vm_ioctl_enable_cap(struct kvm

*kvm,

arch/x86/kvm/x86.c int kvm_vm_ioctl_enable_cap(struct kvm

Quoted 7 lines

                          struct kvm_enable_cap *cap)  {

arch/x86/kvm/x86.c +2 -0

+     struct kvm_vcpu *vcpu;
+     unsigned long i;
      int r;
 
      if (cap->flags)

@@ -6036,14 +6045,17 @@ int kvm_vm_ioctl_enable_cap(struct kvm

*kvm,

arch/x86/kvm/x86.c int kvm_vm_ioctl_enable_cap(struct kvm *kvm, · line 6048

Quoted 6 lines

arch/x86/kvm/x86.c +1 -2

                      break;
 
              mutex_lock(&kvm->lock);
-             if (kvm->created_vcpus)
-                     goto disable_exits_unlock;
+             if (kvm->created_vcpus) {

I retract my comment about using a request, I got ahead of myself.

Don't update vCPUs, the whole point of adding the !kvm->created_vcpus check was to avoid having to update vCPUs when the per-VM behavior changed.

In other words, keep the restriction and drop the request.

Quoted 18 lines

arch/x86/kvm/x86.c +6 -2

+                     kvm_for_each_vcpu(i, vcpu, kvm) {
+                             kvm_ioctl_disable_exits(vcpu->arch, cap->args[0]);
+                             kvm_make_request(KVM_REQ_DISABLE_EXITS, vcpu);
+                     }
+             }
+             mutex_unlock(&kvm->lock);
 
              kvm_ioctl_disable_exits(kvm->arch, cap->args[0]);
 
              r = 0;
-disable_exits_unlock:
-             mutex_unlock(&kvm->lock);
              break;
      case KVM_CAP_MSR_PLATFORM_INFO:
              kvm->arch.guest_can_read_msr_platform_info =

cap->args[0]; @@ -10175,6 +10187,9 @@ static int
vcpu_enter_guest(struct kvm_vcpu *vcpu)

Quoted 1 line

if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING,

vcpu))

Quoted 12 lines

static_call(kvm_x86_update_cpu_dirty_logging)(vcpu);

arch/x86/kvm/x86.c +4 -1

+
+             if (kvm_check_request(KVM_REQ_DISABLE_EXITS, vcpu))
+
+ static_call(kvm_x86_update_disabled_exits)(vcpu);
      }
 
      if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
--

2.32.0

Quoted 14 lines

arch/x86/kvm/x86.c int kvm_vm_ioctl_enable_cap(struct kvm kvm, · line 6048

Quoted 7 lines

arch/x86/kvm/x86.c +1 -2

@@ -6036,14 +6045,17 @@ int kvm_vm_ioctl_enable_cap(struct kvm kvm,
                      break;
 
              mutex_lock(&kvm->lock);
-             if (kvm->created_vcpus)
-                     goto disable_exits_unlock;
+             if (kvm->created_vcpus) {

I retract my comment about using a request, I got ahead of myself.

Don't update vCPUs, the whole point of adding the !kvm->created_vcpus check was to avoid having to update vCPUs when the per-VM behavior changed.

Quoted 2 lines

In other words, keep the restriction and drop the request.

I see. If we keep the restriction here and not updating vCPUs when kvm->created_vcpus is true, the per-VM and per-vCPU assumption would be different here? Not sure if I understand right:
For per-VM, we assume the per-VM cap enabling is only before vcpus creation. For per-vCPU cap enabling, we are able to toggle the disabled exits runtime.

If I understand correctly, this also makes sense though.

-----Original Message-----
From: Sean Christopherson <[email protected]>
Sent: Wednesday, July 20, 2022 12:30 PM
To: Kechen Lu <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Somdutta Roy <[email protected]>; linux- [email protected]
Subject: Re: [RFC PATCH v4 5/7] KVM: x86: add vCPU scoped toggling for disabled exits

External email: Use caution opening links or attachments

Quoted 1 line · Kechen Lu

Quoted 1 line

Review int kvm_vm_ioctl_enable_cap(struct kvm

Quoted 1 line

(quoted diff) +0 -0

@@ -6036,14 +6045,17 @@ int kvm_vm_ioctl_enable_cap(struct kvm

kvm,

Quoted 13 lines

Quoted 13 lines

arch/x86/kvm/x86.c int kvm_vm_ioctl_enable_cap(struct kvm *kvm, · line 6048

Quoted 6 lines

arch/x86/kvm/x86.c +1 -2

                      break;
 
              mutex_lock(&kvm->lock);
-             if (kvm->created_vcpus)
-                     goto disable_exits_unlock;
+             if (kvm->created_vcpus) {

I retract my comment about using a request, I got ahead of myself.

Don't update vCPUs, the whole point of adding the !kvm->created_vcpus check was to avoid having to update vCPUs when the per-VM behavior changed.

Quoted 8 lines

Quoted 2 lines

In other words, keep the restriction and drop the request.

I see. If we keep the restriction here and not updating vCPUs when kvm->created_vcpus is true, the per-VM and per-vCPU assumption would kvm->be
different here? Not sure if I understand right:
For per-VM, we assume the per-VM cap enabling is only before vcpus

creation.

Quoted 1 line

For per-vCPU cap enabling, we are able to toggle the disabled exits runtime.

Yep. The main reason being that there's no use case for changing per-VM settings after vCPUs are created. I.e. we could lift the restriction in the future if a use case pops up, but until then, keep things simple.

Quoted 1 line

If I understand correctly, this also makes sense though.

Paging this all back in...

There are two (sane) options for defining KVM's ABI:

1) KVM combines the per-VM and per-vCPU settings
2) The per-vCPU settings override the per-VM settings

This series implements (2).

For (1), KVM would need to recheck the per-VM state during the per-vCPU update, e.g. instead of simply modifying the per-vCPU flags, the vCPU-scoped handler for KVM_CAP_X86_DISABLE_EXITS would need to merge the incoming settings with the existing kvm->arch.xxx_in_guest flags.

I like (2) because it's simpler to implement and document (merging state is always
messy) and is more flexible. E.g. with (1), the only way to have per-vCPU settings is for userspace to NOT set the per-VM disables and then set disables on a per-vCPU basis. Whereas with (2), userspace can set (or not) the per-VM disables and then override as needed.

For debug and test purposes, there are needs to explicitly make instruction triggered exits could be trapped to userspace. Simply add a new flag for guest_debug interface could achieve this.

This patch also fills the userspace accessible field vcpu->run->hw.hardware_exit_reason for userspace to determine the original triggered VM-exits.

-----Original Message-----
From: Sean Christopherson <[email protected]>
Sent: Wednesday, July 20, 2022 10:06 AM
To: Kechen Lu <[email protected]>
Cc: [email protected]; [email protected]; [email protected]; [email protected]; Somdutta Roy <[email protected]>; linux- [email protected]
Subject: Re: [RFC PATCH v4 6/7] KVM: x86: Add a new guest_debug flag forcing exit to userspace

External email: Use caution opening links or attachments

Quoted 7 lines · Kechen Lu

For debug and test purposes, there are needs to explicitly make instruction triggered exits could be trapped to userspace. Simply add a new flag for guest_debug interface could achieve this.

This patch also fills the userspace accessible field vcpu->run->hw.hardware_exit_reason for userspace to determine the original triggered VM-exits.

This patch belongs in a different series, AFAICT there are no dependencies between this and allowing per-vCPU disabling of exits. Allowing userspace to exit on "every" instruction exit is going to be much more controversial, largely because it will be difficult for KVM to provide a consistent, robust ABI. E.g. should KVM exit to userspace if an intercepted instruction is encountered by the emualtor?

TL;DR: drop this patch from the next version.

Add tests for KVM cap KVM_CAP_X86_DISABLE_EXITS overriding flags in VM and vCPU scope both works as expected.

Suggested-by Chao Gao <[email protected]>

Signed-off-by Kechen Lu <[email protected]>

---
  tools/testing/selftests/kvm/.gitignore        |   1 +
  tools/testing/selftests/kvm/Makefile          |   1 +
  .../selftests/kvm/include/x86_64/svm_util.h   |   1 +
  .../selftests/kvm/x86_64/disable_exits_test.c | 145 ++++++++++++++++++
  4 files changed, 148 insertions(+)

create mode 100644 tools/testing/selftests/kvm/x86_64/disable_exits_test.c

tools/testing/selftests/kvm/.gitignore +1 -0

index 4509a3a7eeae..2b50170db9b2 100644
@@ -15,6 +15,7 @@
  /x86_64/cpuid_test
  /x86_64/cr4_cpuid_sync_test
  /x86_64/debug_regs
+/x86_64/disable_exits_test
  /x86_64/evmcs_test
  /x86_64/emulator_error_test
  /x86_64/fix_hypercall_test

tools/testing/selftests/kvm/Makefile +1 -0

index 22423c871ed6..de11d1f95700 100644
@@ -115,6 +115,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/xen_shinfo_test
  TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_test
  TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests
  TEST_GEN_PROGS_x86_64 += x86_64/amx_test
+TEST_GEN_PROGS_x86_64 += x86_64/disable_exits_test
  TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
  TEST_GEN_PROGS_x86_64 += demand_paging_test
  TEST_GEN_PROGS_x86_64 += dirty_log_test

tools/testing/selftests/kvm/include/x86_64/svm_util.h +0 -0

index a25aabd8f5e7..d8cad1cff578 100644

tools/testing/selftests/kvm/include/x86_64/svm_util.h +0 -0

  #define SVM_EXIT_VMMCALL	0x081
 
  struct svm_test_data {

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +14 -0

new file mode 100644
index 000000000000..2811b07e8885
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test per-VM and per-vCPU disable exits cap
+ *
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "svm_util.h"
+#include "vmx.h"
+#include "processor.h"

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +20 -0

+	};
+	struct kvm_vm *vm;
+	struct kvm_run *run;
+
+	/* Create VM */
+	vm = vm_create_without_vcpus(VM_MODE_DEFAULT, DEFAULT_GUEST_PHY_PAGES);
+
+	/* Test Case #1
+	 * Default without disabling HLT exits in VM scope
+	 */
+	vm_vcpu_add_default(vm, VCPU_ID_1, (void *)guest_code_exits);
+	vcpu_set_debug_exit_userspace(vm, VCPU_ID_1);
+	run = vcpu_state(vm, VCPU_ID_1);
+	vcpu_run(vm, VCPU_ID_1);
+	/* Exit reason should be HLT */
+	if (is_amd_cpu())
+		TEST_ASSERT(run->hw.hardware_exit_reason == SVM_EXIT_HLT,
+			"Got exit_reason other than HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+	else

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +81 -0

+	/* Set VM scoped cap arg
+	 * KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE
+	 * after vCPUs creation so requiring override flag
+	 */
+	TEST_ASSERT(!vm_enable_cap(vm, &cap), "Failed to set KVM_CAP_X86_DISABLE_EXITS");
+	vcpu_run(vm, VCPU_ID_2);
+	/* Exit reason should not be HLT, would finish the guest
+	 * running and exit (e.g. SVM_EXIT_SHUTDOWN)
+	 */
+	if (is_amd_cpu())
+		TEST_ASSERT(run->hw.hardware_exit_reason != SVM_EXIT_HLT,
+			"Got exit_reason as HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+	else
+		TEST_ASSERT(run->hw.hardware_exit_reason != EXIT_REASON_HLT,
+			"Got exit_reason as HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+
+	kvm_vm_free(vm);
+}
+
+static void test_vcpu_cap_disable_exits(void) {
+	struct kvm_enable_cap cap = {
+		.cap = KVM_CAP_X86_DISABLE_EXITS,
+		.args[0] = KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE,
+	};
+	struct kvm_vm *vm;
+	struct kvm_run *run;
+
+	/* Create VM */
+	vm = vm_create_without_vcpus(VM_MODE_DEFAULT, DEFAULT_GUEST_PHY_PAGES);
+	vm_vcpu_add_default(vm, VCPU_ID_1, (void *)guest_code_exits);
+	vcpu_set_debug_exit_userspace(vm, VCPU_ID_1);
+	vm_vcpu_add_default(vm, VCPU_ID_2, (void *)guest_code_exits);
+	vcpu_set_debug_exit_userspace(vm, VCPU_ID_2);
+	/* Set vCPU 2 scoped cap arg
+	 * KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE
+	 */
+	TEST_ASSERT(!vcpu_enable_cap(vm, VCPU_ID_2, &cap), "Failed to set KVM_CAP_X86_DISABLE_EXITS");
+
+	/* Test Case #3
+	 * Default without disabling HLT exits in this vCPU 1
+	 */
+	run = vcpu_state(vm, VCPU_ID_1);
+	vcpu_run(vm, VCPU_ID_1);
+	/* Exit reason should be HLT */
+	if (is_amd_cpu())
+		TEST_ASSERT(run->hw.hardware_exit_reason == SVM_EXIT_HLT,
+			"Got exit_reason other than HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+	else
+		TEST_ASSERT(run->hw.hardware_exit_reason == EXIT_REASON_HLT,
+			"Got exit_reason other than HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+
+	/* Test Case #4
+	 * Disabling HLT exits in vCPU 2
+	 */
+	run = vcpu_state(vm, VCPU_ID_2);
+	vcpu_run(vm, VCPU_ID_2);
+	/* Exit reason should not be HLT, would finish the guest
+	 * running and exit (e.g. SVM_EXIT_SHUTDOWN)
+	 */
+	if (is_amd_cpu())
+		TEST_ASSERT(run->hw.hardware_exit_reason != SVM_EXIT_HLT,
+			"Got exit_reason as HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+	else
+		TEST_ASSERT(run->hw.hardware_exit_reason != EXIT_REASON_HLT,
+			"Got exit_reason as HLT: 0x%llx\n",
+			run->hw.hardware_exit_reason);
+
+	kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+	test_vm_cap_disable_exits();
+	test_vcpu_cap_disable_exits();
+	return 0;
+}

-----Original Message-----
From: Huang, Shaoqin <[email protected]>
Sent: Tuesday, June 21, 2022 11:44 PM
To: Kechen Lu <[email protected]>; [email protected]; [email protected]
Cc: [email protected]; [email protected]; [email protected]; Somdutta Roy <[email protected]>; [email protected]
Subject: Re: [RFC PATCH v4 7/7] KVM: selftests: Add tests for VM and vCPU cap KVM_CAP_X86_DISABLE_EXITS

External email: Use caution opening links or attachments

Quoted 1 line · Kechen Lu

Add tests for KVM cap KVM_CAP_X86_DISABLE_EXITS overriding flags in

VM

tools/testing/selftests/kvm/Makefile TEST_GEN_PROGS_x86_64 +=

Quoted 32 lines

and vCPU scope both works as expected.

Suggested-by Chao Gao <[email protected]>

Signed-off-by Kechen Lu <[email protected]>

---
  tools/testing/selftests/kvm/.gitignore        |   1 +
  tools/testing/selftests/kvm/Makefile          |   1 +
  .../selftests/kvm/include/x86_64/svm_util.h   |   1 +
  .../selftests/kvm/x86_64/disable_exits_test.c | 145 ++++++++++++++++++
  4 files changed, 148 insertions(+)

create mode 100644
tools/testing/selftests/kvm/x86_64/disable_exits_test.c

tools/testing/selftests/kvm/.gitignore +1 -0

index 4509a3a7eeae..2b50170db9b2 100644
@@ -15,6 +15,7 @@
  /x86_64/cpuid_test
  /x86_64/cr4_cpuid_sync_test
  /x86_64/debug_regs
+/x86_64/disable_exits_test
  /x86_64/evmcs_test
  /x86_64/emulator_error_test
  /x86_64/fix_hypercall_test

tools/testing/selftests/kvm/Makefile +0 -0

index 22423c871ed6..de11d1f95700 100644
@@ -115,6 +115,7 @@ TEST_GEN_PROGS_x86_64 +=

x86_64/xen_shinfo_test

Quoted 15 lines

tools/testing/selftests/kvm/Makefile +1 -0

  TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_test
  TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests
  TEST_GEN_PROGS_x86_64 += x86_64/amx_test
+TEST_GEN_PROGS_x86_64 += x86_64/disable_exits_test
  TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
  TEST_GEN_PROGS_x86_64 += demand_paging_test
  TEST_GEN_PROGS_x86_64 += dirty_log_test diff --git

a/tools/testing/selftests/kvm/include/x86_64/svm_util.h b/tools/testing/selftests/kvm/include/x86_64/svm_util.h index a25aabd8f5e7..d8cad1cff578 100644

tools/testing/selftests/kvm/include/x86_64/svm_util.h +0 -0

@@ -17,6 +17,7 @@
  #define CPUID_SVM           BIT_ULL(CPUID_SVM_BIT)
 

tools/testing/selftests/kvm/include/x86_64/svm_util.h line 20

Quoted 2 lines

tools/testing/selftests/kvm/include/x86_64/svm_util.h +1 -0

  #define SVM_EXIT_MSR                0x07c
+#define SVM_EXIT_HLT         0x078

There has other people add the SVM_EXIT_HLT in the kvm/queue, so you may not need to add it here.

Quoted 10 lines

tools/testing/selftests/kvm/include/x86_64/svm_util.h +0 -0

  #define SVM_EXIT_VMMCALL    0x081
 
  struct svm_test_data {

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +0 -0

new file mode 100644
index 000000000000..2811b07e8885

tools/testing/selftests/kvm/x86_64/disable_exits_test.c line 7

Quoted 7 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +7 -0

@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test per-VM and per-vCPU disable exits cap
+ *
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */

#include

Quoted 8 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +8 -0

+<sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "svm_util.h"
+#include "vmx.h"
+#include "processor.h"
+

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+#define VCPU_ID_1 0
+#define VCPU_ID_2 1
+
+static void guest_code_exits(void) {
+     asm volatile("sti; hlt; cli");
+}
+
+/* Set debug control for trapped instruction exiting to userspace */
+static void vcpu_set_debug_exit_userspace(struct kvm_vm *vm, int
+vcpu_id) {

nit: you should make the code style consistent, please use the format:
function()
{

}

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 3 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +3 -0

+     struct kvm_guest_debug debug;
+     memset(&debug, 0, sizeof(debug));
+     debug.control = KVM_GUESTDBG_ENABLE |

KVM_GUESTDBG_EXIT_USERSPACE;

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 7 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +7 -0

+     vcpu_set_guest_debug(vm, vcpu_id, &debug); }
+
+static void test_vm_cap_disable_exits(void) {
+     struct kvm_enable_cap cap = {
+             .cap = KVM_CAP_X86_DISABLE_EXITS,
+             .args[0] =
+KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE,

^
nit: a space is much more clear here

Quoted 12 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +12 -0

+     };
+     struct kvm_vm *vm;
+     struct kvm_run *run;
+
+     /* Create VM */
+     vm = vm_create_without_vcpus(VM_MODE_DEFAULT,
+ DEFAULT_GUEST_PHY_PAGES);
+
+     /* Test Case #1
+      * Default without disabling HLT exits in VM scope
+      */
+     vm_vcpu_add_default(vm, VCPU_ID_1, (void *)guest_code_exits);

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+     vcpu_set_debug_exit_userspace(vm, VCPU_ID_1);
+     run = vcpu_state(vm, VCPU_ID_1);
+     vcpu_run(vm, VCPU_ID_1);
+     /* Exit reason should be HLT */
+     if (is_amd_cpu())
+             TEST_ASSERT(run->hw.hardware_exit_reason == SVM_EXIT_HLT,
+                     "Got exit_reason other than HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+     else
+             TEST_ASSERT(run->hw.hardware_exit_reason ==

EXIT_REASON_HLT,

tools/testing/selftests/kvm/x86_64/disable_exits_test.c line 64

Quoted 9 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +9 -0

+                     "Got exit_reason other than HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+
+     /* Test Case #2
+      * Disabling HLT exits in VM scope
+      */
+     vm_vcpu_add_default(vm, VCPU_ID_2, (void *)guest_code_exits);
+     vcpu_set_debug_exit_userspace(vm, VCPU_ID_2);
+     run = vcpu_state(vm, VCPU_ID_2);

I think you can add more vcpu here to make sure after disabling HLT exits in VM scope here, every vcpu will not exit due to the HLT.

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 5 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +5 -0

+     /* Set VM scoped cap arg
+      * KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE
+      * after vCPUs creation so requiring override flag
+      */
+     TEST_ASSERT(!vm_enable_cap(vm, &cap), "Failed to set

KVM_CAP_X86_DISABLE_EXITS");

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+     vcpu_run(vm, VCPU_ID_2);
+     /* Exit reason should not be HLT, would finish the guest
+      * running and exit (e.g. SVM_EXIT_SHUTDOWN)
+      */
+     if (is_amd_cpu())
+             TEST_ASSERT(run->hw.hardware_exit_reason != SVM_EXIT_HLT,
+                     "Got exit_reason as HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+     else
+             TEST_ASSERT(run->hw.hardware_exit_reason !=

EXIT_REASON_HLT,

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+                     "Got exit_reason as HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+
+     kvm_vm_free(vm);
+}
+
+static void test_vcpu_cap_disable_exits(void) {
+     struct kvm_enable_cap cap = {
+             .cap = KVM_CAP_X86_DISABLE_EXITS,
+             .args[0] =

KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE,

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 6 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +6 -0

+     };
+     struct kvm_vm *vm;
+     struct kvm_run *run;
+
+     /* Create VM */
+     vm = vm_create_without_vcpus(VM_MODE_DEFAULT,

DEFAULT_GUEST_PHY_PAGES);

Quoted 12 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +12 -0

+     vm_vcpu_add_default(vm, VCPU_ID_1, (void *)guest_code_exits);
+     vcpu_set_debug_exit_userspace(vm, VCPU_ID_1);
+     vm_vcpu_add_default(vm, VCPU_ID_2, (void *)guest_code_exits);
+     vcpu_set_debug_exit_userspace(vm, VCPU_ID_2);
+     /* Set vCPU 2 scoped cap arg
+      * KVM_X86_DISABLE_EXITS_HLT|KVM_X86_DISABLE_EXITS_OVERRIDE
+      */
+     TEST_ASSERT(!vcpu_enable_cap(vm, VCPU_ID_2, &cap), "Failed to
+ set KVM_CAP_X86_DISABLE_EXITS");
+
+     /* Test Case #3
+      * Default without disabling HLT exits in this vCPU 1

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+      */
+     run = vcpu_state(vm, VCPU_ID_1);
+     vcpu_run(vm, VCPU_ID_1);
+     /* Exit reason should be HLT */
+     if (is_amd_cpu())
+             TEST_ASSERT(run->hw.hardware_exit_reason == SVM_EXIT_HLT,
+                     "Got exit_reason other than HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+     else
+             TEST_ASSERT(run->hw.hardware_exit_reason ==

EXIT_REASON_HLT,

Quoted 7 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +7 -0

+                     "Got exit_reason other than HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+
+     /* Test Case #4
+      * Disabling HLT exits in vCPU 2
+      */
+     run = vcpu_state(vm, VCPU_ID_2);

tools/testing/selftests/kvm/x86_64/disable_exits_test.c

Quoted 10 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +10 -0

+     vcpu_run(vm, VCPU_ID_2);
+     /* Exit reason should not be HLT, would finish the guest
+      * running and exit (e.g. SVM_EXIT_SHUTDOWN)
+      */
+     if (is_amd_cpu())
+             TEST_ASSERT(run->hw.hardware_exit_reason != SVM_EXIT_HLT,
+                     "Got exit_reason as HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+     else
+             TEST_ASSERT(run->hw.hardware_exit_reason !=

EXIT_REASON_HLT,

Quoted 12 lines

tools/testing/selftests/kvm/x86_64/disable_exits_test.c new file +12 -0

+                     "Got exit_reason as HLT: 0x%llx\n",
+                     run->hw.hardware_exit_reason);
+
+     kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+     test_vm_cap_disable_exits();
+     test_vcpu_cap_disable_exits();
+     return 0;
+}