From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> Move the detection of write #PF to shadow pages, i.e. a fault on a write to a page table that is being shadowed by KVM that is used to translate the write itself, from FNAME(is_self_change_mapping) to FNAME(fetch). There is no need to detect the self-referential write before kvm_faultin_pfn() as KVM does not consume EMULTYPE_WRITE_PF_TO_SP for accesses that resolve to "error or no-slot" pfns, i.e. KVM doesn't allow retrying MMIO accesses or writes to read-only memslots. Detecting the EMULTYPE_WRITE_PF_TO_SP scenario in FNAME(fetch) will allow dropping FNAME(is_self_change_mapping) entirely, as the hugepage interaction can be deferred to kvm_mmu_hugepage_adjust(). Cc: Huang Hang <hhuang@xxxxxxxxxxxxxxxxx> Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221213125538.81209-1-jiangshanlai@xxxxxxxxx [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/mmu/paging_tmpl.h | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 5d2958299b4f..f57d9074fb9b 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -685,6 +685,9 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, if (sp != ERR_PTR(-EEXIST)) link_shadow_page(vcpu, it.sptep, sp); + + if (fault->write && table_gfn == fault->gfn) + fault->write_fault_to_shadow_pgtable = true; } kvm_mmu_hugepage_adjust(vcpu, fault); @@ -741,17 +744,13 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, * created when kvm establishes shadow page table that stop kvm using large * page size. Do it early can avoid unnecessary #PF and emulation. * - * @write_fault_to_shadow_pgtable will return true if the fault gfn is - * currently used as its page table. - * * Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok * since the PDPT is always shadowed, that means, we can not use large page * size to map the gfn which is used as PDPT. */ static bool FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu, - struct guest_walker *walker, bool user_fault, - bool *write_fault_to_shadow_pgtable) + struct guest_walker *walker, bool user_fault) { int level; gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1); @@ -765,7 +764,6 @@ FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu, gfn_t gfn = walker->gfn ^ walker->table_gfn[level - 1]; self_changed |= !(gfn & mask); - *write_fault_to_shadow_pgtable |= !gfn; } return self_changed; @@ -826,7 +824,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault return r; is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu, - &walker, fault->user, &fault->write_fault_to_shadow_pgtable); + &walker, fault->user); if (is_self_change_mapping) fault->max_level = PG_LEVEL_4K; -- 2.39.1.519.gcb327c4b5f-goog
