KVM: MMU: lazily drop large spte (c126d94f) · Commits · 戴 / test

arch/x86/kvm/mmu.c

+18 −16

Original line number	Diff line number	Diff line
		@@ -1176,8 +1176,7 @@ static void drop_large_spte(struct kvm_vcpu vcpu, u64 sptep)

		/*
		* Write-protect on the specified @sptep, @pt_protect indicates whether
		* spte writ-protection is caused by protecting shadow page table.
		* @flush indicates whether tlb need be flushed.
		* spte write-protection is caused by protecting shadow page table.
		*
		* Note: write protection is difference between drity logging and spte
		* protection:
		@@ -1186,10 +1185,9 @@ static void drop_large_spte(struct kvm_vcpu vcpu, u64 sptep)
		* - for spte protection, the spte can be writable only after unsync-ing
		* shadow page.
		*
		* Return true if the spte is dropped.
		* Return true if tlb need be flushed.
		*/
		static bool
		spte_write_protect(struct kvm kvm, u64 sptep, bool *flush, bool pt_protect)
		static bool spte_write_protect(struct kvm kvm, u64 sptep, bool pt_protect)
		{
		u64 spte = *sptep;

		@@ -1199,17 +1197,11 @@ spte_write_protect(struct kvm kvm, u64 sptep, bool *flush, bool pt_protect)

		rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);

		if (__drop_large_spte(kvm, sptep)) {
		*flush \|= true;
		return true;
		}

		if (pt_protect)
		spte &= ~SPTE_MMU_WRITEABLE;
		spte = spte & ~PT_WRITABLE_MASK;

		*flush \|= mmu_spte_update(sptep, spte);
		return false;
		return mmu_spte_update(sptep, spte);
		}

		static bool __rmap_write_protect(struct kvm kvm, unsigned long rmapp,
		@@ -1221,11 +1213,8 @@ static bool __rmap_write_protect(struct kvm kvm, unsigned long rmapp,

		for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
		BUG_ON(!(*sptep & PT_PRESENT_MASK));
		if (spte_write_protect(kvm, sptep, &flush, pt_protect)) {
		sptep = rmap_get_first(*rmapp, &iter);
		continue;
		}

		flush \|= spte_write_protect(kvm, sptep, pt_protect);
		sptep = rmap_get_next(&iter);
		}

		@@ -2876,6 +2865,19 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
		if (!spte_is_locklessly_modifiable(spte))
		goto exit;

		/*
		* Do not fix write-permission on the large spte since we only dirty
		* the first page into the dirty-bitmap in fast_pf_fix_direct_spte()
		* that means other pages are missed if its slot is dirty-logged.
		*
		* Instead, we let the slow page fault path create a normal spte to
		* fix the access.
		*
		* See the comments in kvm_arch_commit_memory_region().
		*/
		if (sp->role.level > PT_PAGE_TABLE_LEVEL)
		goto exit;

		/*
		* Currently, fast page fault only works for direct mapping since
		* the gfn is not stable for indirect shadow page.

arch/x86/kvm/x86.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -7315,8 +7315,12 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
		kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
		/*
		* Write protect all pages for dirty logging.
		* Existing largepage mappings are destroyed here and new ones will
		* not be created until the end of the logging.
		*
		* All the sptes including the large sptes which point to this
		* slot are set to readonly. We can not create any new large
		* spte on this slot until the end of the logging.
		*
		* See the comments in fast_page_fault().
		*/
		if ((change != KVM_MR_DELETE) && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
		kvm_mmu_slot_remove_write_access(kvm, mem->slot);

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