On 12/9/22 22:03, Sean Christopherson wrote:
From: Sean Christopherson<seanjc@xxxxxxxxxx>
Date: Fri, 9 Dec 2022 12:55:44 -0800
Subject: [PATCH] KVM: selftests: Use magic value to signal ucall_alloc()
failure
Use a magic value to signal a ucall_alloc() failure instead of simply
doing GUEST_ASSERT(). GUEST_ASSERT() relies on ucall_alloc() and so a
failure puts the guest into an infinite loop.
Use -1 as the magic value, as a real ucall struct should never wrap.
Reported-by: Oliver Upton<oliver.upton@xxxxxxxxx>
Signed-off-by: Sean Christopherson<seanjc@xxxxxxxxxx>
---
tools/testing/selftests/kvm/lib/ucall_common.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
index 0cc0971ce60e..2f0e2ea941cc 100644
--- a/tools/testing/selftests/kvm/lib/ucall_common.c
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -4,6 +4,8 @@
#include "linux/bitmap.h"
#include "linux/atomic.h"
+#define GUEST_UCALL_FAILED -1
+
struct ucall_header {
DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
struct ucall ucalls[KVM_MAX_VCPUS];
@@ -41,7 +43,8 @@ static struct ucall *ucall_alloc(void)
struct ucall *uc;
int i;
- GUEST_ASSERT(ucall_pool);
+ if (!ucall_pool)
+ goto ucall_failed;
for (i = 0; i < KVM_MAX_VCPUS; ++i) {
if (!test_and_set_bit(i, ucall_pool->in_use)) {
@@ -51,7 +54,13 @@ static struct ucall *ucall_alloc(void)
}
}
- GUEST_ASSERT(0);
+ucall_failed:
+ /*
+ * If the vCPU cannot grab a ucall structure, make a bare ucall with a
+ * magic value to signal to get_ucall() that things went sideways.
+ * GUEST_ASSERT() depends on ucall_alloc() and so cannot be used here.
+ */
+ ucall_arch_do_ucall(GUEST_UCALL_FAILED);
return NULL;
}
@@ -93,6 +102,9 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
addr = ucall_arch_get_ucall(vcpu);
if (addr) {
+ TEST_ASSERT(addr != (void *)GUEST_UCALL_FAILED,
+ "Guest failed to allocate ucall struct");
+
memcpy(uc, addr, sizeof(*uc));
vcpu_run_complete_io(vcpu);
} else {
base-commit: dc2efbe4813e0dc4368779bc36c5f0e636cb8eb2
--
Queued, thanks.
Paolo
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