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 this in the 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(). Faults are necessarily ephemeral and pre-faulting can't guarantee what may happen in parallel, so do not store the GFN or PFN in kvm_s2_fault_result. Pre-faulting only needs to know what was mapped in at the point of the fault. This struct could be replaced with a pointer to an unsigned long, however it's clearer to separate out the mapped flag and having a struct allows us to easily add additional fields in future as needed. No functional change intended. Suggested-by: Vincent Donnefort <[email protected]> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> --- arch/arm64/kvm/mmu.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 80cb520e25b9..da15da4e40e6 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1607,6 +1607,11 @@ struct kvm_s2_fault_desc { struct kvm_s2_mmu *mmu; }; +struct kvm_s2_fault_result { + unsigned long mapping_size; + bool mapped; +}; + static bool kvm_s2_fault_is_perm(const struct kvm_s2_fault_desc *s2fd) { return esr_fsc_is_permission_fault(s2fd->esr); @@ -1632,7 +1637,17 @@ 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 void populate_fault_result(struct kvm_s2_fault_result *result, + unsigned long mapping_size) +{ + /* A THP upgrade may have altered mapping size. */ + result->mapping_size = mapping_size; + /* -EAGAIN is swallowed so be explicit when we actually map. */ + result->mapped = true; +} + +static int gmem_abort(const struct kvm_s2_fault_desc *s2fd, + struct kvm_s2_fault_result *result) { bool write_fault, exec_fault; const bool perm_fault = kvm_s2_fault_is_perm(s2fd); @@ -1714,6 +1729,8 @@ 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); + if (result && !ret) + populate_fault_result(result, PAGE_SIZE); return ret != -EAGAIN ? ret : 0; } @@ -2038,7 +2055,8 @@ 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; bool writable = prot & KVM_PGTABLE_PROT_W; @@ -2117,12 +2135,15 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd, mark_page_dirty_in_slot(kvm, s2fd->memslot, gpa_to_gfn(ipa)); } + if (result && !ret) + populate_fault_result(result, mapping_size); if (ret != -EAGAIN) return ret; return 0; } -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) { const bool perm_fault = kvm_s2_fault_is_perm(s2fd); struct kvm_s2_fault_vma_info s2vi = {}; @@ -2161,7 +2182,7 @@ 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. */ @@ -2440,9 +2461,9 @@ 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
