Refactor handling flow of SET_CPUID*

PATCH Superseded Xiaoyao Li 2 participants 9 messages May 29, 2020 – Jun 3, 2020

Subsystems (3)

x86 KVM KVM x86

lore

Share & tools

lore

Xiaoyao Li

author

2020-05-29 08:55 UTC #0 lore raw

cover Refactor handling flow of SET_CPUID*

This serial is the extended version of
https://lkml.kernel.org/r/[email protected]

First two patches are bug fixing, and the other aim to refactor the flow of SET_CPUID* as:
1. cpuid check: check if userspace provides legal CPUID settings;

2. cpuid update: Update some special CPUID bits based on current vcpu

                 state, e.g., OSXSAVE, OSPKE, ...

3. update KVM state: Update KVM states based on the final CPUID settings.

Xiaoyao Li (6):
KVM: X86: Reset vcpu->arch.cpuid_nent to 0 if SET_CPUID fails
KVM: X86: Go on updating other CPUID leaves when leaf 1 is absent
KVM: X86: Introduce kvm_check_cpuid()
KVM: X86: Split kvm_update_cpuid()
KVM: X86: Move kvm_x86_ops.cpuid_update() into
kvm_update_state_based_on_cpuid()
KVM: X86: Move kvm_apic_set_version() to
kvm_update_state_based_on_cpuid()

 arch/x86/kvm/cpuid.c | 107 +++++++++++++++++++++++++++----------------
 arch/x86/kvm/cpuid.h |   3 +-
 arch/x86/kvm/x86.c   |   1 +
 3 files changed, 70 insertions(+), 41 deletions(-)

Signature · 1 line

2.18.2

Xiaoyao Li

author

2020-05-29 08:55 UTC #1 lore raw

PATCH 1/6 KVM: X86: Reset vcpu->arch.cpuid_nent to 0 if SET_CPUID fails

It needs to invalidate CPUID configruations if usersapce provides illegal input.

Signed-off-by Xiaoyao Li <[email protected]>

---
 arch/x86/kvm/cpuid.c | 4 ++++
 1 file changed, 4 insertions(+)

arch/x86/kvm/cpuid.c +4 -0

index cd708b0b460a..2f1a9650b7f2 100644
@@ -210,6 +210,8 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
 	r = kvm_update_cpuid(vcpu);
+	if (r)
+		vcpu->arch.cpuid_nent = 0;
 
 out:
 	vfree(cpuid_entries);

@@ -233,6 +235,8 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
 	r = kvm_update_cpuid(vcpu);
+	if (r)
+		vcpu->arch.cpuid_nent = 0;
 out:
 	return r;
 }

Signature · 1 line

2.18.2

Xiaoyao Li

author

2020-05-29 08:55 UTC #2 lore raw

PATCH 2/6 KVM: X86: Go on updating other CPUID leaves when leaf 1 is absent

In reply to Xiaoyao Li

As handling of bits other leaf 1 added over time, kvm_update_cpuid() should not return directly if leaf 1 is absent, but should go on updateing other CPUID leaves.

Signed-off-by Xiaoyao Li <[email protected]>

---
 arch/x86/kvm/cpuid.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

arch/x86/kvm/cpuid.c +11 ~~-12~~

index 2f1a9650b7f2..795bbaf37110 100644
@@ -60,22 +60,21 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
 	best = kvm_find_cpuid_entry(vcpu, 1, 0);
-	if (!best)
-		return 0;
-
-	/* Update OSXSAVE bit */
-	if (boot_cpu_has(X86_FEATURE_XSAVE) && best->function == 0x1)
-		cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
+	if (best) {
+		/* Update OSXSAVE bit */
+		if (boot_cpu_has(X86_FEATURE_XSAVE))
+			cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
 				   kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE));
 
-	cpuid_entry_change(best, X86_FEATURE_APIC,
+		cpuid_entry_change(best, X86_FEATURE_APIC,
 			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
 
-	if (apic) {
-		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
-			apic->lapic_timer.timer_mode_mask = 3 << 17;
-		else
-			apic->lapic_timer.timer_mode_mask = 1 << 17;
+		if (apic) {
+			if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
+				apic->lapic_timer.timer_mode_mask = 3 << 17;
+			else
+				apic->lapic_timer.timer_mode_mask = 1 << 17;
+		}
 	}
 
 	best = kvm_find_cpuid_entry(vcpu, 7, 0);

Signature · 1 line

2.18.2

Xiaoyao Li

author

2020-05-29 08:56 UTC #3 lore raw

PATCH 3/6 KVM: X86: Introduce kvm_check_cpuid()

In reply to Xiaoyao Li

Use kvm_check_cpuid() to validate if userspace provides legal cpuid settings and call it before KVM updates CPUID.

Signed-off-by Xiaoyao Li <[email protected]>

---
Is the check of virutal address width really necessary?
KVM doesn't check other bits at all. I guess the policy is that KVM allows illegal CPUID settings as long as it doesn't break host kernel. Userspace takes the consequences itself if it sets bogus CPUID settings that breaks its guest.
But why vaddr_bits is special? It seems illegal vaddr_bits won't break host kernel.

---
 arch/x86/kvm/cpuid.c | 54 ++++++++++++++++++++++++++++----------------
 arch/x86/kvm/cpuid.h |  2 +-
 2 files changed, 35 insertions(+), 21 deletions(-)

arch/x86/kvm/cpuid.c +34 ~~-20~~

index 795bbaf37110..c8cb373056f1 100644
@@ -54,7 +54,26 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
 
 #define F feature_bit
 
-int kvm_update_cpuid(struct kvm_vcpu *vcpu)
+static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *best;
+
+	/*
+	 * The existing code assumes virtual address is 48-bit or 57-bit in the
+	 * canonical address checks; exit if it is ever changed.
+	 */
+	best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
+	if (best) {
+		int vaddr_bits = (best->eax & 0xff00) >> 8;
+
+		if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best;
 	struct kvm_lapic *apic = vcpu->arch.apic;

@@ -96,18 +115,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 		     cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
 		best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
 
-	/*
-	 * The existing code assumes virtual address is 48-bit or 57-bit in the
-	 * canonical address checks; exit if it is ever changed.
-	 */
-	best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
-	if (best) {
-		int vaddr_bits = (best->eax & 0xff00) >> 8;
-
-		if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
-			return -EINVAL;
-	}
-
 	best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
 	if (kvm_hlt_in_guest(vcpu->kvm) && best &&
 		(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))

@@ -127,7 +134,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 	kvm_mmu_reset_context(vcpu);
 
 	kvm_pmu_refresh(vcpu);
-	return 0;
 }
 
 static int is_efer_nx(void)

@@ -205,12 +211,16 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 		vcpu->arch.cpuid_entries[i].padding[2] = 0;
 	}
 	vcpu->arch.cpuid_nent = cpuid->nent;
+	r = kvm_check_cpuid(vcpu);
+	if (r) {
+		vcpu->arch.cpuid_nent = 0;
+		goto out;
+	}
+
 	cpuid_fix_nx_cap(vcpu);
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
-	r = kvm_update_cpuid(vcpu);
-	if (r)
-		vcpu->arch.cpuid_nent = 0;
+	kvm_update_cpuid(vcpu);
 
 out:
 	vfree(cpuid_entries);

@@ -231,11 +241,15 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 			   cpuid->nent * sizeof(struct kvm_cpuid_entry2)))
 		goto out;
 	vcpu->arch.cpuid_nent = cpuid->nent;
+	r = kvm_check_cpuid(vcpu);
+	if (r) {
+		vcpu->arch.cpuid_nent = 0;
+		goto out;
+	}
+
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
-	r = kvm_update_cpuid(vcpu);
-	if (r)
-		vcpu->arch.cpuid_nent = 0;
+	kvm_update_cpuid(vcpu);
 out:
 	return r;
 }

arch/x86/kvm/cpuid.h +1 -1

index 05434cd9342f..f136de1debad 100644
@@ -9,7 +9,7 @@
 extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
 void kvm_set_cpu_caps(void);
 
-int kvm_update_cpuid(struct kvm_vcpu *vcpu);
+void kvm_update_cpuid(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
 					      u32 function, u32 index);
 int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

Signature · 1 line

2.18.2

Xiaoyao Li

author

2020-05-29 08:56 UTC #4 lore raw

PATCH 4/6 KVM: X86: Split kvm_update_cpuid()

In reply to Xiaoyao Li

Split the part of updating KVM states from kvm_update_cpuid(), and put it into a new kvm_update_state_based_on_cpuid(). So it's clear that kvm_update_cpuid() is to update guest CPUID settings, while kvm_update_state_based_on_cpuid() is to update KVM states based on the updated CPUID settings.

Signed-off-by Xiaoyao Li <[email protected]>

---
 arch/x86/kvm/cpuid.c | 38 ++++++++++++++++++++++++--------------
 arch/x86/kvm/cpuid.h |  1 +
 arch/x86/kvm/x86.c   |  1 +
 3 files changed, 26 insertions(+), 14 deletions(-)

arch/x86/kvm/cpuid.c +24 ~~-14~~

index c8cb373056f1..a4a2072f5253 100644
@@ -76,7 +76,6 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
 void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best;
-	struct kvm_lapic *apic = vcpu->arch.apic;
 
 	best = kvm_find_cpuid_entry(vcpu, 1, 0);
 	if (best) {

@@ -87,13 +86,6 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 
 		cpuid_entry_change(best, X86_FEATURE_APIC,
 			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
-
-		if (apic) {
-			if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
-				apic->lapic_timer.timer_mode_mask = 3 << 17;
-			else
-				apic->lapic_timer.timer_mode_mask = 1 << 17;
-		}
 	}
 
 	best = kvm_find_cpuid_entry(vcpu, 7, 0);

@@ -102,13 +94,8 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 				   kvm_read_cr4_bits(vcpu, X86_CR4_PKE));
 
 	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
-	if (!best) {
-		vcpu->arch.guest_supported_xcr0 = 0;
-	} else {
-		vcpu->arch.guest_supported_xcr0 =
-			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
+	if (best)
 		best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
-	}
 
 	best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
 	if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||

@@ -127,6 +114,27 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 					   vcpu->arch.ia32_misc_enable_msr &
 					   MSR_IA32_MISC_ENABLE_MWAIT);
 	}
+}
+
+void kvm_update_state_based_on_cpuid(struct kvm_vcpu *vcpu)
+{
+	struct kvm_lapic *apic = vcpu->arch.apic;
+	struct kvm_cpuid_entry2 *best;
+
+	best = kvm_find_cpuid_entry(vcpu, 1, 0);
+	if (best && apic) {
+		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
+			apic->lapic_timer.timer_mode_mask = 3 << 17;
+		else
+			apic->lapic_timer.timer_mode_mask = 1 << 17;
+	}
+
+	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
+	if (!best)
+		vcpu->arch.guest_supported_xcr0 = 0;
+	else
+		vcpu->arch.guest_supported_xcr0 =
+			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
 
 	/* Note, maxphyaddr must be updated before tdp_level. */
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);

@@ -221,6 +229,7 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
 	kvm_update_cpuid(vcpu);
+	kvm_update_state_based_on_cpuid(vcpu);
 
 out:
 	vfree(cpuid_entries);

@@ -250,6 +259,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops.cpuid_update(vcpu);
 	kvm_update_cpuid(vcpu);
+	kvm_update_state_based_on_cpuid(vcpu);
 out:
 	return r;
 }

arch/x86/kvm/cpuid.h +1 -0

index f136de1debad..0ccf9ec4bf55 100644
@@ -10,6 +10,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
 void kvm_set_cpu_caps(void);
 
 void kvm_update_cpuid(struct kvm_vcpu *vcpu);
+void kvm_update_state_based_on_cpuid(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
 					      u32 function, u32 index);
 int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

arch/x86/kvm/x86.c +1 -0

index dc993b79ae2f..fcb85432d30b 100644
@@ -8100,6 +8100,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 #endif
 
 	kvm_update_cpuid(vcpu);
+	kvm_update_state_based_on_cpuid(vcpu);
 	kvm_mmu_reset_context(vcpu);
 }

Signature · 1 line

2.18.2

Sean Christopherson

2020-06-03 01:11 UTC #5 lore raw

Re: [PATCH 4/6] KVM: X86: Split kvm_update_cpuid()

Quoted 5 lines · Xiaoyao Li

Split the part of updating KVM states from kvm_update_cpuid(), and put it into a new kvm_update_state_based_on_cpuid(). So it's clear that kvm_update_cpuid() is to update guest CPUID settings, while kvm_update_state_based_on_cpuid() is to update KVM states based on the updated CPUID settings.

What about kvm_update_vcpu_model()? "state" isn't necessarily correct either.

Xiaoyao Li

author

2020-06-03 07:44 UTC #6 lore raw

Re: [PATCH 4/6] KVM: X86: Split kvm_update_cpuid()

Quoted 10 lines · Sean Christopherson

Quoted 5 lines · Xiaoyao Li
Split the part of updating KVM states from kvm_update_cpuid(), and put it into a new kvm_update_state_based_on_cpuid(). So it's clear that kvm_update_cpuid() is to update guest CPUID settings, while kvm_update_state_based_on_cpuid() is to update KVM states based on the updated CPUID settings.
What about kvm_update_vcpu_model()? "state" isn't necessarily correct either.

yeah, it's better.

Xiaoyao Li

author

2020-05-29 08:56 UTC #7 lore raw

PATCH 5/6 KVM: X86: Move kvm_x86_ops.cpuid_update() into kvm_update_state_based_on_cpuid()

In reply to Xiaoyao Li

kvm_x86_ops.cpuid_update() is used to update vmx/svm settings based on updated CPUID settings. So it's supposed to be called after CPUIDs are fully updated, i.e., kvm_update_cpuid(), not in the middle stage.

Put it in kvm_update_state_based_on_cpuid() to make it clear that it's to update vmx/svm specific states based on CPUID.

Signed-off-by Xiaoyao Li <[email protected]>

---
Should we rename kvm_x86_ops.cpuid_update to something like kvm_x86_ops.update_state_based_on_cpuid?

cpuid_update is really confusing especially when kvm_x86_ops.update_cpuid() is needed someday.

---
 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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

index a4a2072f5253..5d4da8970940 100644
@@ -136,6 +136,8 @@ void kvm_update_state_based_on_cpuid(struct kvm_vcpu *vcpu)
 		vcpu->arch.guest_supported_xcr0 =
 			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
 
+	kvm_x86_ops.cpuid_update(vcpu);
+
 	/* Note, maxphyaddr must be updated before tdp_level. */
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
 	vcpu->arch.tdp_level = kvm_x86_ops.get_tdp_level(vcpu);

@@ -227,7 +229,6 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 
 	cpuid_fix_nx_cap(vcpu);
 	kvm_apic_set_version(vcpu);
-	kvm_x86_ops.cpuid_update(vcpu);
 	kvm_update_cpuid(vcpu);
 	kvm_update_state_based_on_cpuid(vcpu);

@@ -257,7 +258,6 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 	}
 
 	kvm_apic_set_version(vcpu);
-	kvm_x86_ops.cpuid_update(vcpu);
 	kvm_update_cpuid(vcpu);
 	kvm_update_state_based_on_cpuid(vcpu);
 out:

Signature · 1 line

2.18.2

Xiaoyao Li

author

2020-05-29 08:56 UTC #8 lore raw

PATCH 6/6 KVM: X86: Move kvm_apic_set_version() to kvm_update_state_based_on_cpuid()

In reply to Xiaoyao Li

Obviously, kvm_apic_set_version() fits well in
kvm_update_state_based_on_cpuid().

Signed-off-by Xiaoyao Li <[email protected]>

---
 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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

index 5d4da8970940..eb60098aca29 100644
@@ -127,6 +127,8 @@ void kvm_update_state_based_on_cpuid(struct kvm_vcpu *vcpu)
 			apic->lapic_timer.timer_mode_mask = 3 << 17;
 		else
 			apic->lapic_timer.timer_mode_mask = 1 << 17;
+
+		kvm_apic_set_version(vcpu);
 	}
 
 	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);

@@ -228,7 +230,6 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 	}
 
 	cpuid_fix_nx_cap(vcpu);
-	kvm_apic_set_version(vcpu);
 	kvm_update_cpuid(vcpu);
 	kvm_update_state_based_on_cpuid(vcpu);

@@ -257,7 +258,6 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 		goto out;
 	}
 
-	kvm_apic_set_version(vcpu);
 	kvm_update_cpuid(vcpu);
 	kvm_update_state_based_on_cpuid(vcpu);
 out:

Signature · 1 line

2.18.2