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KVM: VMX: Clean up RTIT MAXPHYADDR usage

PATCH Superseded Sean Christopherson 1 participant 4 messages Jul 16, 2020

Subsystems (3)
x86 KVM KVM x86

v1 of 3 Superseded Latest is v3 →

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Sean Christopherson

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#0 lore raw

cover KVM: VMX: Clean up RTIT MAXPHYADDR usage

Stop using cpuid_query_maxphyaddr() for a random RTIT MSR check and unexport said function to discourage future use.

Sean Christopherson (3):
KVM: VMX: Use precomputed MAXPHYADDR for RTIT base MSR check
KVM: VMX: Replace MSR_IA32_RTIT_OUTPUT_BASE_MASK with helper function
KVM: x86: Unexport cpuid_query_maxphyaddr()

 arch/x86/kvm/cpuid.c   |  1 -
 arch/x86/kvm/vmx/vmx.c | 11 +++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)
Signature · 1 line
2.26.0
author
#1 lore raw

PATCH 1/3 KVM: VMX: Use precomputed MAXPHYADDR for RTIT base MSR check

Use cpuid_maxphyaddr() instead of cpuid_query_maxphyaddr() for the RTIT base MSR check. There is no reason to recompute MAXPHYADDR as the precomputed version is synchronized with CPUID updates, and MSR_IA32_RTIT_OUTPUT_BASE is not written between stuffing CPUID and refreshing vcpu->arch.maxphyaddr.

Signed-off-by Sean Christopherson <[email protected]>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/kvm/vmx/vmx.c +1 -1
index 1bb59ae5016dc..50b7e85d37352 100644
@@ -146,7 +146,7 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO);
 	RTIT_STATUS_BYTECNT))
 
 #define MSR_IA32_RTIT_OUTPUT_BASE_MASK \
-	(~((1UL << cpuid_query_maxphyaddr(vcpu)) - 1) | 0x7f)
+	(~((1UL << cpuid_maxphyaddr(vcpu)) - 1) | 0x7f)
 
 /*
  * These 2 parameters are used to config the controls for Pause-Loop Exiting:
Signature · 1 line
2.26.0
author
#2 lore raw

PATCH 2/3 KVM: VMX: Replace MSR_IA32_RTIT_OUTPUT_BASE_MASK with helper function

In reply to Sean Christopherson

Replace the subtly not-a-constant MSR_IA32_RTIT_OUTPUT_BASE_MASK with a proper helper function to check whether or not the specified base is valid. Blindly referencing the local 'vcpu' is especially nasty.

Signed-off-by Sean Christopherson <[email protected]>
---
 arch/x86/kvm/vmx/vmx.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
arch/x86/kvm/vmx/vmx.c +7 -4
index 50b7e85d37352..cf3c3562e843c 100644
@@ -145,9 +145,6 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO);
 	RTIT_STATUS_ERROR | RTIT_STATUS_STOPPED | \
 	RTIT_STATUS_BYTECNT))
 
-#define MSR_IA32_RTIT_OUTPUT_BASE_MASK \
-	(~((1UL << cpuid_maxphyaddr(vcpu)) - 1) | 0x7f)
-
 /*
  * These 2 parameters are used to config the controls for Pause-Loop Exiting:
  * ple_gap:    upper bound on the amount of time between two successive

@@ -1036,6 +1033,12 @@ static inline bool pt_can_write_msr(struct vcpu_vmx *vmx)
 	       !(vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN);
 }
 
+static inline bool pt_output_base_valid(struct kvm_vcpu *vcpu, u64 base)
+{
+	/* The base must be 128-byte aligned and a legal physical address. */
+	return !(base & (~((1UL << cpuid_maxphyaddr(vcpu)) - 1) | 0x7f));
+}
+
 static inline void pt_load_msr(struct pt_ctx *ctx, u32 addr_range)
 {
 	u32 i;

@@ -2193,7 +2196,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		    !intel_pt_validate_cap(vmx->pt_desc.caps,
 					   PT_CAP_single_range_output))
 			return 1;
-		if (data & MSR_IA32_RTIT_OUTPUT_BASE_MASK)
+		if (!pt_output_base_valid(vcpu, data))
 			return 1;
 		vmx->pt_desc.guest.output_base = data;
 		break;
Signature · 1 line
2.26.0
author
#3 lore raw

PATCH 3/3 KVM: x86: Unexport cpuid_query_maxphyaddr()

In reply to Sean Christopherson

Stop exporting cpuid_query_maxphyaddr() now that it's not being abused by VMX.

Signed-off-by Sean Christopherson <[email protected]>
---
 arch/x86/kvm/cpuid.c | 1 -
 1 file changed, 1 deletion(-)
arch/x86/kvm/cpuid.c +0 -1
index 7d92854082a14..e4a8065fbddd7 100644
@@ -188,7 +188,6 @@ int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)
 not_found:
 	return 36;
 }
-EXPORT_SYMBOL_GPL(cpuid_query_maxphyaddr);
 
 /* when an old userspace process fills a new kernel module */
 int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
Signature · 1 line
2.26.0