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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 15/09/20 00:13, Sean Christopherson wrote:
>> +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*().

No, kvm_post_set_cr0 is exactly the right name because it doesn't set
any state. __kvm_set_cr0 tells me that it is a (rarely used) way to set
CR0, which this function isn't.

Sorry Tom for not catching this earlier.

Paolo

>> +{
>> + 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);

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