Add RET_PF_CONTINUE and use it in handle_abnormal_pfn() and kvm_faultin_pfn() to signal that the page fault handler should continue doing its thing. Aside from being gross and inefficient, using a boolean return to signal continue vs. stop makes it extremely difficult to add more helpers and/or move existing code to a helper. E.g. hypothetically, if nested MMUs were to gain a separate page fault handler in the future, everything up to the "is self-modifying PTE" check can be shared by all shadow MMUs, but communicating up the stack whether to continue on or stop becomes a nightmare. More concretely, proposed support for private guest memory ran into a similar issue, where it'll be forced to forego a helper in order to yield sane code: https://lore.kernel.org/all/YkJbxiL%2FAz7olWlq@xxxxxxxxxx. No functional change intended. Cc: David Matlack <dmatlack@xxxxxxxxxx> Cc: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/mmu/mmu.c | 51 ++++++++++++++------------------- arch/x86/kvm/mmu/mmu_internal.h | 9 +++++- arch/x86/kvm/mmu/paging_tmpl.h | 6 ++-- 3 files changed, 34 insertions(+), 32 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 69a30d6d1e2b..cb2982c6b513 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2972,14 +2972,12 @@ static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn) return -EFAULT; } -static bool handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, - unsigned int access, int *ret_val) +static int handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, + unsigned int access) { /* The pfn is invalid, report the error! */ - if (unlikely(is_error_pfn(fault->pfn))) { - *ret_val = kvm_handle_bad_page(vcpu, fault->gfn, fault->pfn); - return true; - } + if (unlikely(is_error_pfn(fault->pfn))) + return kvm_handle_bad_page(vcpu, fault->gfn, fault->pfn); if (unlikely(!fault->slot)) { gva_t gva = fault->is_tdp ? 0 : fault->addr; @@ -2991,13 +2989,11 @@ static bool handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fa * touching the shadow page tables as attempting to install an * MMIO SPTE will just be an expensive nop. */ - if (unlikely(!shadow_mmio_value)) { - *ret_val = RET_PF_EMULATE; - return true; - } + if (unlikely(!shadow_mmio_value)) + return RET_PF_EMULATE; } - return false; + return RET_PF_CONTINUE; } static bool page_fault_can_be_fast(struct kvm_page_fault *fault) @@ -3888,7 +3884,7 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch); } -static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, int *r) +static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot; bool async; @@ -3899,7 +3895,7 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, * be zapped before KVM inserts a new MMIO SPTE for the gfn. */ if (slot && (slot->flags & KVM_MEMSLOT_INVALID)) - goto out_retry; + return RET_PF_RETRY; if (!kvm_is_visible_memslot(slot)) { /* Don't expose private memslots to L2. */ @@ -3907,7 +3903,7 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, fault->slot = NULL; fault->pfn = KVM_PFN_NOSLOT; fault->map_writable = false; - return false; + return RET_PF_CONTINUE; } /* * If the APIC access page exists but is disabled, go directly @@ -3916,10 +3912,8 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, * when the AVIC is re-enabled. */ if (slot && slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT && - !kvm_apicv_activated(vcpu->kvm)) { - *r = RET_PF_EMULATE; - return true; - } + !kvm_apicv_activated(vcpu->kvm)) + return RET_PF_EMULATE; } async = false; @@ -3927,26 +3921,23 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, fault->write, &fault->map_writable, &fault->hva); if (!async) - return false; /* *pfn has correct page already */ + return RET_PF_CONTINUE; /* *pfn has correct page already */ if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) { trace_kvm_try_async_get_page(fault->addr, fault->gfn); if (kvm_find_async_pf_gfn(vcpu, fault->gfn)) { trace_kvm_async_pf_doublefault(fault->addr, fault->gfn); kvm_make_request(KVM_REQ_APF_HALT, vcpu); - goto out_retry; - } else if (kvm_arch_setup_async_pf(vcpu, fault->addr, fault->gfn)) - goto out_retry; + return RET_PF_RETRY; + } else if (kvm_arch_setup_async_pf(vcpu, fault->addr, fault->gfn)) { + return RET_PF_RETRY; + } } fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, NULL, fault->write, &fault->map_writable, &fault->hva); - return false; - -out_retry: - *r = RET_PF_RETRY; - return true; + return RET_PF_CONTINUE; } /* @@ -4001,10 +3992,12 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); - if (kvm_faultin_pfn(vcpu, fault, &r)) + r = kvm_faultin_pfn(vcpu, fault); + if (r != RET_PF_CONTINUE) return r; - if (handle_abnormal_pfn(vcpu, fault, ACC_ALL, &r)) + r = handle_abnormal_pfn(vcpu, fault, ACC_ALL); + if (r != RET_PF_CONTINUE) return r; r = RET_PF_RETRY; diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 1bff453f7cbe..c0e502b17ef7 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -143,6 +143,7 @@ unsigned int pte_list_count(struct kvm_rmap_head *rmap_head); /* * Return values of handle_mmio_page_fault, mmu.page_fault, and fast_page_fault(). * + * RET_PF_CONTINUE: So far, so good, keep handling the page fault. * RET_PF_RETRY: let CPU fault again on the address. * RET_PF_EMULATE: mmio page fault, emulate the instruction directly. * RET_PF_INVALID: the spte is invalid, let the real page fault path update it. @@ -151,9 +152,15 @@ unsigned int pte_list_count(struct kvm_rmap_head *rmap_head); * * Any names added to this enum should be exported to userspace for use in * tracepoints via TRACE_DEFINE_ENUM() in mmutrace.h + * + * Note, all values must be greater than or equal to zero so as not to encroach + * on -errno return values. Somewhat arbitrarily use '0' for CONTINUE, which + * will allow for efficient machine code when checking for CONTINUE, e.g. + * "TEST %rax, %rax, JNZ", as all "stop!" values are non-zero. */ enum { - RET_PF_RETRY = 0, + RET_PF_CONTINUE = 0, + RET_PF_RETRY, RET_PF_EMULATE, RET_PF_INVALID, RET_PF_FIXED, diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 66f1acf153c4..7038273d04ab 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -838,10 +838,12 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); - if (kvm_faultin_pfn(vcpu, fault, &r)) + r = kvm_faultin_pfn(vcpu, fault); + if (r != RET_PF_CONTINUE) return r; - if (handle_abnormal_pfn(vcpu, fault, walker.pte_access, &r)) + r = handle_abnormal_pfn(vcpu, fault, walker.pte_access); + if (r != RET_PF_CONTINUE) return r; /* base-commit: 150866cd0ec871c765181d145aa0912628289c8a -- 2.36.0.rc0.470.gd361397f0d-goog
