Wrap the TDP MMU page counter in CONFIG_KVM_PROVE_MMU so that the sanity
check is omitted from production builds, and more importantly to remove
the atomic accesses to account pages. A one-off memory leak in production
is relatively uninteresting, and a WARN_ON won't help mitigate a systemic
issue; it's as much about helping triage memory leaks as it is about
detecting them in the first place, and doesn't magically stop the leaks.
I.e. production environments will be quite sad if a severe KVM bug escapes,
regardless of whether or not KVM WARNs.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 7 ++++++-
arch/x86/kvm/mmu/tdp_mmu.c | 8 +++++++-
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d881e7d276b1..30b81a81a1c7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1471,8 +1471,13 @@ struct kvm_arch {
struct once nx_once;
#ifdef CONFIG_X86_64
- /* The number of TDP MMU pages across all roots. */
+#ifdef CONFIG_KVM_PROVE_MMU
+ /*
+ * The number of TDP MMU pages across all roots. Used only to sanity
+ * check that KVM isn't leaking TDP MMU pages.
+ */
atomic64_t tdp_mmu_pages;
+#endif
/*
* List of struct kvm_mmu_pages being used as roots.
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7cc0564f5f97..21a3b8166242 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -40,7 +40,9 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
kvm_tdp_mmu_invalidate_roots(kvm, KVM_VALID_ROOTS);
kvm_tdp_mmu_zap_invalidated_roots(kvm, false);
- WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages));
+#ifdef CONFIG_KVM_PROVE_MMU
+ KVM_MMU_WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages));
+#endif
WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));
/*
@@ -325,13 +327,17 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
static void tdp_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
kvm_account_pgtable_pages((void *)sp->spt, +1);
+#ifdef CONFIG_KVM_PROVE_MMU
atomic64_inc(&kvm->arch.tdp_mmu_pages);
+#endif
}
static void tdp_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
kvm_account_pgtable_pages((void *)sp->spt, -1);
+#ifdef CONFIG_KVM_PROVE_MMU
atomic64_dec(&kvm->arch.tdp_mmu_pages);
+#endif
}
/**
base-commit: 7d2154117a02832ab3643fe2da4cdc9d2090dcb2
--
2.49.0.rc1.451.g8f38331e32-goog
