Commit 58da926c authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Cleanup sanity check of SPTEs at SP free 

Massage the error message for the sanity check on SPTEs when freeing a
shadow page to be more verbose, and to print out all shadow-present SPTEs,
not just the first SPTE encountered.  Printing all SPTEs can be quite
valuable for debug, e.g. highlights whether the leak is a one-off or
widepsread, or possibly the result of memory corruption (something else
in the kernel stomping on KVM's SPTEs).

Opportunistically move the MMU_WARN_ON() into the helper itself, which
will allow a future cleanup to use BUILD_BUG_ON_INVALID() as the stub for
MMU_WARN_ON().  BUILD_BUG_ON_INVALID() works as intended and results in
the compiler complaining about is_empty_shadow_page() not being declared.

Link: https://lore.kernel.org/r/20230729004722.1056172-6-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 242a6dd8

arch/x86/kvm/mmu/mmu.c

+9 −10
Original line number Diff line number Diff line
@@ -1689,21 +1689,19 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) 
	return young;

}



#ifdef MMU_DEBUG

static int is_empty_shadow_page(u64 *spt)

static void kvm_mmu_check_sptes_at_free(struct kvm_mmu_page *sp)

{

#ifdef MMU_DEBUG

	int i;



	for (i = 0; i < SPTE_ENT_PER_PAGE; i++) {

		if (is_shadow_present_pte(spt[i])) {

			printk(KERN_ERR "%s: %p %llx\n", __func__,

			       &spt[i], spt[i]);

			return 0;

		}

	}

	return 1;

		if (MMU_WARN_ON(is_shadow_present_pte(sp->spt[i])))

			pr_err_ratelimited("SPTE %llx (@ %p) for gfn %llx shadow-present at free",

					   sp->spt[i], &sp->spt[i],

					   kvm_mmu_page_get_gfn(sp, i));

	}

#endif

}



/*

 * This value is the sum of all of the kvm instances's
@@ -1731,7 +1729,8 @@ static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) 


static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp)

{

	MMU_WARN_ON(!is_empty_shadow_page(sp->spt));

	kvm_mmu_check_sptes_at_free(sp);



	hlist_del(&sp->hash_link);

	list_del(&sp->link);

	free_page((unsigned long)sp->spt);