linux-kernel - [PATCH 2/8] KVM: selftests: Close VM's binary stats FD when releasing VM

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Message-ID: <20241220013906.3518334-3-seanjc@google.com>
Date: Thu, 19 Dec 2024 17:39:00 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, Sean Christopherson <seanjc@...gle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/8] KVM: selftests: Close VM's binary stats FD when releasing VM

Close/free a VM's binary stats cache when the VM is released, not when the
VM is fully freed.  When a VM is re-created, e.g. for state save/restore
tests, the stats FD and descriptor points at the old, defunct VM.  The FD
is still valid, in that the underlying stats file won't be freed until the
FD is closed, but reading stats will always pull information from the old
VM.

Note, this is a benign bug in the current code base as none of the tests
that recreate VMs use binary stats.

Fixes: 83f6e109f562 ("KVM: selftests: Cache binary stats metadata for duration of test")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 91d295ef5d02..9138801ecb60 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -709,6 +709,15 @@ void kvm_vm_release(struct kvm_vm *vmp)
 
 	ret = close(vmp->kvm_fd);
 	TEST_ASSERT(!ret,  __KVM_SYSCALL_ERROR("close()", ret));
+
+	/* Free cached stats metadata and close FD */
+	if (vmp->stats_desc) {
+		free(vmp->stats_desc);
+		vmp->stats_desc = NULL;
+
+		ret = close(vmp->stats_fd);
+		TEST_ASSERT(!ret,  __KVM_SYSCALL_ERROR("close()", ret));
+	}
 }
 
 static void __vm_mem_region_delete(struct kvm_vm *vm,
@@ -748,12 +757,6 @@ void kvm_vm_free(struct kvm_vm *vmp)
 	if (vmp == NULL)
 		return;
 
-	/* Free cached stats metadata and close FD */
-	if (vmp->stats_desc) {
-		free(vmp->stats_desc);
-		close(vmp->stats_fd);
-	}
-
 	/* Free userspace_mem_regions. */
 	hash_for_each_safe(vmp->regions.slot_hash, ctr, node, region, slot_node)
 		__vm_mem_region_delete(vmp, region);
-- 
2.47.1.613.gc27f4b7a9f-goog