On Wed, Mar 15, 2023 at 02:17:34AM +0000,
Anish Moorthy <amoorthy@xxxxxxxxxx> wrote:
> When a memslot has the KVM_MEM_MEMORY_FAULT_EXIT flag set, exit to
> userspace upon encountering a page fault for which the userspace
> page tables do not contain a present mapping.
> ---
> arch/x86/kvm/mmu/mmu.c | 33 +++++++++++++++++++++++++--------
> arch/x86/kvm/x86.c | 1 +
> 2 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 5e0140db384f6..68bc4ab2bd942 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3214,7 +3214,9 @@ static void kvm_send_hwpoison_signal(struct kvm_memory_slot *slot, gfn_t gfn)
> send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva, PAGE_SHIFT, current);
> }
>
> -static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> +static int kvm_handle_error_pfn(
> + struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
> + bool faulted_on_absent_mapping)
> {
> if (is_sigpending_pfn(fault->pfn)) {
> kvm_handle_signal_exit(vcpu);
> @@ -3234,7 +3236,11 @@ static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fa
> return RET_PF_RETRY;
> }
>
> - return -EFAULT;
> + return kvm_memfault_exit_or_efault(
> + vcpu, fault->gfn * PAGE_SIZE, PAGE_SIZE,
> + faulted_on_absent_mapping
> + ? KVM_MEMFAULT_REASON_ABSENT_MAPPING
> + : KVM_MEMFAULT_REASON_UNKNOWN);
> }
>
> static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
> @@ -4209,7 +4215,9 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, 0, true);
> }
>
> -static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> +static int __kvm_faultin_pfn(
> + struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
> + bool fault_on_absent_mapping)
> {
> struct kvm_memory_slot *slot = fault->slot;
> bool async;
> @@ -4242,9 +4250,15 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> }
>
> async = false;
> - fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
> - fault->write, &fault->map_writable,
> - &fault->hva);
> +
> + fault->pfn = __gfn_to_pfn_memslot(
> + slot, fault->gfn,
> + fault_on_absent_mapping,
> + false,
> + fault_on_absent_mapping ? NULL : &async,
> + fault->write, &fault->map_writable,
> + &fault->hva);
> +
> if (!async)
> return RET_PF_CONTINUE; /* *pfn has correct page already */
>
> @@ -4274,16 +4288,19 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
> unsigned int access)
> {
> int ret;
> + bool fault_on_absent_mapping
> + = likely(fault->slot) && kvm_slot_fault_on_absent_mapping(fault->slot);
nit: Instead of passing around the value, we can add a new member to
struct kvm_page_fault::fault_on_absent_mapping.
fault->fault_on_absent_mapping = likely(fault->slot) && kvm_slot_fault_on_absent_mapping(fault->slot);
Thanks,
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
