Re: [PATCH 3/6] KVM: x86/mmu: Extract __kvm_mmu_do_page_fault()

Xiaoyao Li
2024-04-22T08:46:33Z

On 4/19/2024 4:59 PM, Paolo Bonzini wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Extract out __kvm_mmu_do_page_fault() from kvm_mmu_do_page_fault(). The
> inner function is to initialize struct kvm_page_fault and to call the fault
> handler, and the outer function handles updating stats and converting
> return code.

I don't see how the outer function converts return code.

> KVM_PRE_FAULT_MEMORY will call the KVM page fault handler.

I assume it means the inner function will be used by KVM_PRE_FAULT_MEMORY.

> This patch makes the emulation_type always set irrelevant to the return
> code. kvm_mmu_page_fault() is the only caller of kvm_mmu_do_page_fault(),
> and references the value only when PF_RET_EMULATE is returned. Therefore,
> this adjustment doesn't affect functionality.

This paragraph needs to be removed, I think. It's not true.

> No functional change intended.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Message-ID: <ddf1d98420f562707b11e12c416cce8fdb986bb1.1712785629.git.isaku.yamahata@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/mmu/mmu_internal.h | 38 +++++++++++++++++++++------------
> 1 file changed, 24 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index e68a60974cf4..9baae6c223ee 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -287,8 +287,8 @@ static inline void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
> fault->is_private);
> }
>
> -static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> - u64 err, bool prefetch, int *emulation_type)
> +static inline int __kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> + u64 err, bool prefetch, int *emulation_type)
> {
> struct kvm_page_fault fault = {
> .addr = cr2_or_gpa,
> @@ -318,6 +318,27 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> fault.slot = kvm_vcpu_gfn_to_memslot(vcpu, fault.gfn);
> }
>
> + if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && fault.is_tdp)
> + r = kvm_tdp_page_fault(vcpu, &fault);
> + else
> + r = vcpu->arch.mmu->page_fault(vcpu, &fault);
> +
> + if (r == RET_PF_EMULATE && fault.is_private) {
> + kvm_mmu_prepare_memory_fault_exit(vcpu, &fault);
> + r = -EFAULT;
> + }
> +
> + if (fault.write_fault_to_shadow_pgtable && emulation_type)
> + *emulation_type |= EMULTYPE_WRITE_PF_TO_SP;
> +
> + return r;
> +}
> +
> +static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> + u64 err, bool prefetch, int *emulation_type)
> +{
> + int r;
> +
> /*
> * Async #PF "faults", a.k.a. prefetch faults, are not faults from the
> * guest perspective and have already been counted at the time of the
> @@ -326,18 +347,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> if (!prefetch)
> vcpu->stat.pf_taken++;
>
> - if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && fault.is_tdp)
> - r = kvm_tdp_page_fault(vcpu, &fault);
> - else
> - r = vcpu->arch.mmu->page_fault(vcpu, &fault);
> -
> - if (r == RET_PF_EMULATE && fault.is_private) {
> - kvm_mmu_prepare_memory_fault_exit(vcpu, &fault);
> - return -EFAULT;
> - }
> -
> - if (fault.write_fault_to_shadow_pgtable && emulation_type)
> - *emulation_type |= EMULTYPE_WRITE_PF_TO_SP;
> + r = __kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, err, prefetch, emulation_type);
>
> /*
> * Similar to above, prefetch faults aren't truly spurious, and the