On Wed, 2024-04-10 at 15:07 -0700, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> 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. KVM_MAP_MEMORY will call the KVM page fault handler.
>
> This patch makes the emulation_type always set irrelevant to the return
a comma would help parse this better ^
> code.
> kvm_mmu_page_fault() is the only caller of kvm_mmu_do_page_fault(),
Not technically correct, there are other callers that pass NULL for
emulation_type.
> and references the value only when PF_RET_EMULATE is returned. Therefore,
> this adjustment doesn't affect functionality.
Is there a problem with dropping the argument then?
>
> No functional change intended.
Can we not use the "intended"? It sounds like hedging for excuses.
>
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
> v2:
> - Newly introduced. (Sean)
> ---
> arch/x86/kvm/mmu/mmu_internal.h | 32 +++++++++++++++++++++-----------
> 1 file changed, 21 insertions(+), 11 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,
> @@ -318,14 +318,6 @@ 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);
> }
>
> - /*
> - * 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
> - * original fault.
> - */
> - if (!prefetch)
> - vcpu->stat.pf_taken++;
> -
> if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && fault.is_tdp)
> r = kvm_tdp_page_fault(vcpu, &fault);
> else
> @@ -333,12 +325,30 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu
> *vcpu, gpa_t cr2_or_gpa,
>
> if (r == RET_PF_EMULATE && fault.is_private) {
> kvm_mmu_prepare_memory_fault_exit(vcpu, &fault);
> - return -EFAULT;
> + 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
> + * original fault.
> + */
> + if (!prefetch)
> + vcpu->stat.pf_taken++;
>From the name, it makes sense to not count KVM_MAP_MEMORY as a pf_taken. But
kvm_arch_async_page_ready() increments it as well. Which makes it more like a
"faulted-in" count. I think the code in this patch is ok.
> +
> + 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
> * async #PF path doesn't do emulation. Do count faults that are
> fixed
