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KVM: selftests: Use magic value to signal ucall_alloc() failure

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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@linux.dev>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-12-09 12:55:44 -08:00 • committed by Paolo Bonzini
parent db7b780dab
commit 2f5213b8fc
1 changed files with 14 additions and 2 deletions
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16
tools/testing/selftests/kvm/lib/ucall_common.c
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@ -4,6 +4,8 @@
#include "linux/bitmap.h" #include "linux/bitmap.h"
#include "linux/atomic.h" #include "linux/atomic.h"
#define GUEST_UCALL_FAILED -1
struct ucall_header { struct ucall_header {
DECLARE_BITMAP(in_use, KVM_MAX_VCPUS); DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
struct ucall ucalls[KVM_MAX_VCPUS]; struct ucall ucalls[KVM_MAX_VCPUS];
@ -41,7 +43,8 @@ static struct ucall *ucall_alloc(void)
struct ucall *uc; struct ucall *uc;
int i; int i;
GUEST_ASSERT(ucall_pool); if (!ucall_pool)
goto ucall_failed;
for (i = 0; i < KVM_MAX_VCPUS; ++i) { for (i = 0; i < KVM_MAX_VCPUS; ++i) {
if (!test_and_set_bit(i, ucall_pool->in_use)) { 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; return NULL;
} }
@ -93,6 +102,9 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
addr = ucall_arch_get_ucall(vcpu); addr = ucall_arch_get_ucall(vcpu);
if (addr) { if (addr) {
TEST_ASSERT(addr != (void *)GUEST_UCALL_FAILED,
"Guest failed to allocate ucall struct");
memcpy(uc, addr, sizeof(*uc)); memcpy(uc, addr, sizeof(*uc));
vcpu_run_complete_io(vcpu); vcpu_run_complete_io(vcpu);
} else { } else {