When stage 2 page tables fault the net result may either be that a page is mapped, an error occurred or the fault should be retried (-EAGAIN).
When a fault succeeds it may be upgraded to a PMD size via transparent_hugepage_adjust(). In order to support KVM pre-faulting the outcome of the fault and the mapping size must be recorded. Track the mapping size via new kvm_s2_fault_result struct, which is threaded through gmem_abort(), user_mem_abort() and kvm_s2_fault_map(). PKVM and SEA aren't relevant to synthetic pre-faulting so neither kvm_inject_sea() nor pkvm_mem_abort() are altered. Actual hardware faulting doesn't require this information, so kvm_handle_guest_abort() simply passes NULL kvm_s2_fault_result to gmem_abort() and user_mem_abort(). A non-NULL result also tells the abort handlers that the caller is pre-faulting rather than a vcpu, in which case -EAGAIN is propagated to the caller to allow the pre-fault to be retried. Likewise, only prepare a KVM_EXIT_MEMORY_FAULT in gmem_abort() when a real fault is being handled, as this updates vcpu state. No functional change intended. Suggested-by: Vincent Donnefort <[email protected]> Reviewed-by: Oliver Upton <[email protected]> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> --- arch/arm64/kvm/mmu.c | 43 +++++++++++++++++++++++++++++++------------ 1 file changed, 31 insertions(+), 12 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 9d799f7c1e62..ee2a4f0faa14 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1659,6 +1659,10 @@ struct kvm_s2_fault_desc { struct kvm_s2_mmu *mmu; }; +struct kvm_s2_fault_result { + unsigned long mapping_size; +}; + static bool kvm_s2_fault_is_perm(const struct kvm_s2_fault_desc *s2fd) { return esr_fsc_is_permission_fault(s2fd->esr); @@ -1684,7 +1688,8 @@ static u64 kvm_s2_perm_fault_granule(const struct kvm_s2_fault_desc *s2fd) return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level)); } -static int gmem_abort(const struct kvm_s2_fault_desc *s2fd) +static int gmem_abort(const struct kvm_s2_fault_desc *s2fd, + struct kvm_s2_fault_result *result) { bool write_fault, exec_fault; bool perm_fault = kvm_s2_fault_is_perm(s2fd); @@ -1728,8 +1733,10 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd) ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, &page, NULL); if (ret) { - kvm_prepare_memory_fault_exit(s2fd->vcpu, s2fd->fault_ipa, PAGE_SIZE, - write_fault, exec_fault, false); + /* If result is non-NULL this is a synthetic fault. */ + if (!result) + kvm_prepare_memory_fault_exit(s2fd->vcpu, s2fd->fault_ipa, PAGE_SIZE, + write_fault, exec_fault, false); kfree(mapping); return ret; } @@ -1784,7 +1791,13 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd) if ((prot & KVM_PGTABLE_PROT_W) && !ret) mark_page_dirty_in_slot(kvm, s2fd->memslot, gfn); - return ret != -EAGAIN ? ret : 0; + if (ret == -EAGAIN) + return result ? ret : 0; + + if (result && !ret) + result->mapping_size = PAGE_SIZE; + + return ret; } struct kvm_s2_fault_vma_info { @@ -2108,7 +2121,8 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd, static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd, const struct kvm_s2_fault_vma_info *s2vi, enum kvm_pgtable_prot prot, - void *memcache) + void *memcache, + struct kvm_s2_fault_result *result) { enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_SHARED; struct kvm_guest_s2_mapping *mapping = NULL; @@ -2209,12 +2223,17 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd, mark_page_dirty_in_slot(kvm, s2fd->memslot, gpa_to_gfn(canonical_ipa)); - if (ret != -EAGAIN) - return ret; - return 0; + if (ret == -EAGAIN) + return result ? ret : 0; + + if (result && !ret) + result->mapping_size = mapping_size; + + return ret; } -static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd) +static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd, + struct kvm_s2_fault_result *result) { bool perm_fault = kvm_s2_fault_is_perm(s2fd); struct kvm_s2_fault_vma_info s2vi = {}; @@ -2253,7 +2272,7 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd) return ret; } - return kvm_s2_fault_map(s2fd, &s2vi, prot, memcache); + return kvm_s2_fault_map(s2fd, &s2vi, prot, memcache, result); } /* Resolve the access fault by making the page young again. */ @@ -2532,9 +2551,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) !kvm_s2_fault_is_exec(&s2fd)); if (kvm_slot_has_gmem(memslot)) - ret = gmem_abort(&s2fd); + ret = gmem_abort(&s2fd, NULL); else - ret = user_mem_abort(&s2fd); + ret = user_mem_abort(&s2fd, NULL); } if (ret == 0) -- 2.55.0
