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SubjectRe: [RFC PATCH 22/35] KVM: SVM: Add support for CR0 write traps for an SEV-ES guest
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On 9/14/20 5:13 PM, Sean Christopherson wrote:
> On Mon, Sep 14, 2020 at 03:15:36PM -0500, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index b65bd0c986d4..6f5988c305e1 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -799,11 +799,29 @@ bool pdptrs_changed(struct kvm_vcpu *vcpu)
>> }
>> EXPORT_SYMBOL_GPL(pdptrs_changed);
>>
>> +static void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0,
>> + unsigned long cr0)
>
> What about using __kvm_set_cr*() instead of kvm_post_set_cr*()? That would
> show that __kvm_set_cr*() is a subordinate of kvm_set_cr*(), and from the
> SVM side would provide the hint that the code is skipping the front end of
> kvm_set_cr*().

Ok, I'll change this (and the others) to __kvm_set_cr* and export them.

>
>> +{
>> + unsigned long update_bits = X86_CR0_PG | X86_CR0_WP;
>> +
>> + if ((cr0 ^ old_cr0) & X86_CR0_PG) {
>> + kvm_clear_async_pf_completion_queue(vcpu);
>> + kvm_async_pf_hash_reset(vcpu);
>> + }
>> +
>> + if ((cr0 ^ old_cr0) & update_bits)
>> + kvm_mmu_reset_context(vcpu);
>> +
>> + if (((cr0 ^ old_cr0) & X86_CR0_CD) &&
>> + kvm_arch_has_noncoherent_dma(vcpu->kvm) &&
>> + !kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
>> + kvm_zap_gfn_range(vcpu->kvm, 0, ~0ULL);
>> +}
>> +
>> int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
>> {
>> unsigned long old_cr0 = kvm_read_cr0(vcpu);
>> unsigned long pdptr_bits = X86_CR0_CD | X86_CR0_NW | X86_CR0_PG;
>> - unsigned long update_bits = X86_CR0_PG | X86_CR0_WP;
>>
>> cr0 |= X86_CR0_ET;
>>
>> @@ -842,22 +860,23 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
>>
>> kvm_x86_ops.set_cr0(vcpu, cr0);
>>
>> - if ((cr0 ^ old_cr0) & X86_CR0_PG) {
>> - kvm_clear_async_pf_completion_queue(vcpu);
>> - kvm_async_pf_hash_reset(vcpu);
>> - }
>> + kvm_post_set_cr0(vcpu, old_cr0, cr0);
>>
>> - if ((cr0 ^ old_cr0) & update_bits)
>> - kvm_mmu_reset_context(vcpu);
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(kvm_set_cr0);
>>
>> - if (((cr0 ^ old_cr0) & X86_CR0_CD) &&
>> - kvm_arch_has_noncoherent_dma(vcpu->kvm) &&
>> - !kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
>> - kvm_zap_gfn_range(vcpu->kvm, 0, ~0ULL);
>> +int kvm_track_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
>
> I really dislike the "track" terminology. For me, using "track" as the verb
> in a function implies the function activates tracking. But it's probably a
> moot point, because similar to EFER, I don't see any reason to put the front
> end of the emulation into x86.c. Both getting old_cr0 and setting
> vcpu->arch.cr0 can be done in svm.c

Yup, I can move that to svm.c.

Thanks,
Tom

>
>> +{
>> + unsigned long old_cr0 = kvm_read_cr0(vcpu);
>> +
>> + vcpu->arch.cr0 = cr0;
>> +
>> + kvm_post_set_cr0(vcpu, old_cr0, cr0);
>>
>> return 0;
>> }
>> -EXPORT_SYMBOL_GPL(kvm_set_cr0);
>> +EXPORT_SYMBOL_GPL(kvm_track_cr0);
>>
>> void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
>> {
>> --
>> 2.28.0
>>

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