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KVM: VMX: Open code writing vCPU's PAT in VMX's MSR handler

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Open code setting "vcpu->arch.pat" in vmx_set_msr() instead of bouncing
through kvm_set_msr_common() to get to the same code in kvm_mtrr_set_msr().
This aligns VMX with SVM, avoids hiding a very simple operation behind a
relatively complicated function call (finding the PAT MSR case in
kvm_set_msr_common() is non-trivial), and most importantly, makes it clear
that not unwinding the VMCS updates if kvm_set_msr_common() isn't a bug
(because kvm_set_msr_common() can never fail for PAT).

Opportunistically set vcpu->arch.pat before updating the VMCS info so that
a future patch can move the common bits (back) into kvm_set_msr_common()
without a functional change.

Note, MSR_IA32_CR_PAT is 0x277, and is very subtly handled by

	case 0x200 ... MSR_IA32_MC0_CTL2 - 1:

in kvm_set_msr_common().

Cc: Kai Huang <kai.huang@intel.com>
Signed-off-by: Wenyao Hai <haiwenyao@uniontech.com>
[sean: massage changelog, hoist setting vcpu->arch.pat up]
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230511233351.635053-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Wenyao Hai 2023-05-11 16:33:44 -07:00 committed by Sean Christopherson
parent b9846a698c
commit a33ba1bf0d
1 changed files with 3 additions and 5 deletions
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8
arch/x86/kvm/vmx/vmx.c
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@ -2290,16 +2290,14 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!kvm_pat_valid(data))
return 1;
vcpu->arch.pat = data;
if (is_guest_mode(vcpu) &&
get_vmcs12(vcpu)->vm_exit_controls & VM_EXIT_SAVE_IA32_PAT)
get_vmcs12(vcpu)->guest_ia32_pat = data;
if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT)
vmcs_write64(GUEST_IA32_PAT, data);
vcpu->arch.pat = data;
break;
}
ret = kvm_set_msr_common(vcpu, msr_info);
break;
case MSR_IA32_MCG_EXT_CTL:
if ((!msr_info->host_initiated &&