linux-kernel - [PATCH v8 03/10] KVM: x86: Stuff vCPU's PAT with default value at RESET, not creation

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Message-ID: <20240605231918.2915961-4-seanjc@google.com>
Date: Wed,  5 Jun 2024 16:19:11 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Xiaoyao Li <xiaoyao.li@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Jim Mattson <jmattson@...gle.com>, Shan Kang <shan.kang@...el.com>, Xin Li <xin3.li@...el.com>, 
	Zhao Liu <zhao1.liu@...el.com>
Subject: [PATCH v8 03/10] KVM: x86: Stuff vCPU's PAT with default value at
 RESET, not creation

Move the stuffing of the vCPU's PAT to the architectural "default" value
from kvm_arch_vcpu_create() to kvm_vcpu_reset(), guarded by !init_event,
to better capture that the default value is the value "Following Power-up
or Reset".  E.g. setting PAT only during creation would break if KVM were
to expose a RESET ioctl() to userspace (which is unlikely, but that's not
a good reason to have unintuitive code).

No functional change.

Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>
Reviewed-by: Kai Huang <kai.huang@...el.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4157602c964e..887d29db0e05 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12226,8 +12226,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
 	vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 
-	vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
-
 	kvm_async_pf_hash_reset(vcpu);
 
 	vcpu->arch.perf_capabilities = kvm_caps.supported_perf_cap;
@@ -12393,6 +12391,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	if (!init_event) {
 		vcpu->arch.smbase = 0x30000;
 
+		vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
+
 		vcpu->arch.msr_misc_features_enables = 0;
 		vcpu->arch.ia32_misc_enable_msr = MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL |
 						  MSR_IA32_MISC_ENABLE_BTS_UNAVAIL;
-- 
2.45.1.467.gbab1589fc0-goog