From 641e6808586d76b477c00de804358982b95c8d50 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Mon, 12 Dec 2022 17:01:06 +0800 Subject: [PATCH] kvm: x86/mmu: Warn on linking when sp->unsync_children Since the commit 65855ed8b034 ("KVM: X86: Synchronize the shadow pagetable before link it"), no sp would be linked with sp->unsync_children = 1. So make it WARN if it is the case. Signed-off-by: Lai Jiangshan Message-Id: <20221212090106.378206-1-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 4736d7849c60..26b32ae6b526 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2355,7 +2355,16 @@ static void __link_shadow_page(struct kvm *kvm, mmu_page_add_parent_pte(cache, sp, sptep); - if (sp->unsync_children || sp->unsync) + /* + * The non-direct sub-pagetable must be updated before linking. For + * L1 sp, the pagetable is updated via kvm_sync_page() in + * kvm_mmu_find_shadow_page() without write-protecting the gfn, + * so sp->unsync can be true or false. For higher level non-direct + * sp, the pagetable is updated/synced via mmu_sync_children() in + * FNAME(fetch)(), so sp->unsync_children can only be false. + * WARN_ON_ONCE() if anything happens unexpectedly. + */ + if (WARN_ON_ONCE(sp->unsync_children) || sp->unsync) mark_unsync(sptep); }