From cbd858b17e379f727c6bf1eaedde7b1a44e75b40 Mon Sep 17 00:00:00 2001 From: David Matlack Date: Wed, 22 Jun 2022 15:27:00 -0400 Subject: [PATCH] KVM: x86/mmu: Allow NULL @vcpu in kvm_mmu_find_shadow_page() Allow @vcpu to be NULL in kvm_mmu_find_shadow_page() (and its only caller __kvm_mmu_get_shadow_page()). @vcpu is only required to sync indirect shadow pages, so it's safe to pass in NULL when looking up direct shadow pages. This will be used for doing eager page splitting, which allocates direct shadow pages from the context of a VM ioctl without access to a vCPU pointer. Signed-off-by: David Matlack Message-Id: <20220516232138.1783324-14-dmatlack@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 88b3f3c..a7748c5 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1975,6 +1975,12 @@ static void clear_sp_write_flooding_count(u64 *spte) __clear_sp_write_flooding_count(sptep_to_sp(spte)); } +/* + * The vCPU is required when finding indirect shadow pages; the shadow + * page may already exist and syncing it needs the vCPU pointer in + * order to read guest page tables. Direct shadow pages are never + * unsync, thus @vcpu can be NULL if @role.direct is true. + */ static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm *kvm, struct kvm_vcpu *vcpu, gfn_t gfn, @@ -2013,6 +2019,9 @@ static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm *kvm, goto out; if (sp->unsync) { + if (KVM_BUG_ON(!vcpu, kvm)) + break; + /* * The page is good, but is stale. kvm_sync_page does * get the latest guest state, but (unlike mmu_unsync_children) @@ -2090,6 +2099,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm, return sp; } +/* Note, @vcpu may be NULL if @role.direct is true; see kvm_mmu_find_shadow_page. */ static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm, struct kvm_vcpu *vcpu, struct shadow_page_caches *caches, -- 2.7.4