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KVM: selftests: Add tests in xen_shinfo_test to detect lock races

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Tests for races between shinfo_cache (de)activation and hypercall+ioctl()
processing.  KVM has had bugs where activating the shared info cache
multiple times and/or with concurrent users results in lock corruption,
NULL pointer dereferences, and other fun.

For the timer injection testcase (#22), re-arm the timer until the IRQ
is successfully injected.  If the timer expires while the shared info
is deactivated (invalid), KVM will drop the event.

Signed-off-by: Michal Luczaj <mhal@rbox.co>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221013211234.1318131-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michal Luczaj 2022-10-13 21:12:33 +00:00 committed by Paolo Bonzini
parent ecbcf030b4
commit a51abbbf25
1 changed files with 140 additions and 0 deletions
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140
tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
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@ -15,9 +15,13 @@
#include <time.h>
#include <sched.h>
#include <signal.h>
#include <pthread.h>
#include <sys/eventfd.h>
/* Defined in include/linux/kvm_types.h */
#define GPA_INVALID (~(ulong)0)
#define SHINFO_REGION_GVA 0xc0000000ULL
#define SHINFO_REGION_GPA 0xc0000000ULL
#define SHINFO_REGION_SLOT 10
@ -44,6 +48,8 @@
#define MIN_STEAL_TIME 50000
#define SHINFO_RACE_TIMEOUT 2 /* seconds */
#define __HYPERVISOR_set_timer_op 15
#define __HYPERVISOR_sched_op 29
#define __HYPERVISOR_event_channel_op 32
@ -148,6 +154,7 @@ static void guest_wait_for_irq(void)
static void guest_code(void)
{
struct vcpu_runstate_info *rs = (void *)RUNSTATE_VADDR;
int i;
__asm__ __volatile__(
"sti\n"
@ -325,6 +332,49 @@ static void guest_code(void)
guest_wait_for_irq();
GUEST_SYNC(21);
/* Racing host ioctls */
guest_wait_for_irq();
GUEST_SYNC(22);
/* Racing vmcall against host ioctl */
ports[0] = 0;
p = (struct sched_poll) {
.ports = ports,
.nr_ports = 1,
.timeout = 0
};
wait_for_timer:
/*
* Poll for a timer wake event while the worker thread is mucking with
* the shared info. KVM XEN drops timer IRQs if the shared info is
* invalid when the timer expires. Arbitrarily poll 100 times before
* giving up and asking the VMM to re-arm the timer. 100 polls should
* consume enough time to beat on KVM without taking too long if the
* timer IRQ is dropped due to an invalid event channel.
*/
for (i = 0; i < 100 && !guest_saw_irq; i++)
asm volatile("vmcall"
: "=a" (rax)
: "a" (__HYPERVISOR_sched_op),
"D" (SCHEDOP_poll),
"S" (&p)
: "memory");
/*
* Re-send the timer IRQ if it was (likely) dropped due to the timer
* expiring while the event channel was invalid.
*/
if (!guest_saw_irq) {
GUEST_SYNC(23);
goto wait_for_timer;
}
guest_saw_irq = false;
GUEST_SYNC(24);
}
static int cmp_timespec(struct timespec *a, struct timespec *b)
@ -352,11 +402,36 @@ static void handle_alrm(int sig)
TEST_FAIL("IRQ delivery timed out");
}
static void *juggle_shinfo_state(void *arg)
{
struct kvm_vm *vm = (struct kvm_vm *)arg;
struct kvm_xen_hvm_attr cache_init = {
.type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
.u.shared_info.gfn = SHINFO_REGION_GPA / PAGE_SIZE
};
struct kvm_xen_hvm_attr cache_destroy = {
.type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
.u.shared_info.gfn = GPA_INVALID
};
for (;;) {
__vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_init);
__vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_destroy);
pthread_testcancel();
};
return NULL;
}
int main(int argc, char *argv[])
{
struct timespec min_ts, max_ts, vm_ts;
struct kvm_vm *vm;
pthread_t thread;
bool verbose;
int ret;
verbose = argc > 1 && (!strncmp(argv[1], "-v", 3) ||
!strncmp(argv[1], "--verbose", 10));
@ -785,6 +860,71 @@ int main(int argc, char *argv[])
case 21:
TEST_ASSERT(!evtchn_irq_expected,
"Expected event channel IRQ but it didn't happen");
alarm(0);
if (verbose)
printf("Testing shinfo lock corruption (KVM_XEN_HVM_EVTCHN_SEND)\n");
ret = pthread_create(&thread, NULL, &juggle_shinfo_state, (void *)vm);
TEST_ASSERT(ret == 0, "pthread_create() failed: %s", strerror(ret));
struct kvm_irq_routing_xen_evtchn uxe = {
.port = 1,
.vcpu = vcpu->id,
.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
};
evtchn_irq_expected = true;
for (time_t t = time(NULL) + SHINFO_RACE_TIMEOUT; time(NULL) < t;)
__vm_ioctl(vm, KVM_XEN_HVM_EVTCHN_SEND, &uxe);
break;
case 22:
TEST_ASSERT(!evtchn_irq_expected,
"Expected event channel IRQ but it didn't happen");
if (verbose)
printf("Testing shinfo lock corruption (SCHEDOP_poll)\n");
shinfo->evtchn_pending[0] = 1;
evtchn_irq_expected = true;
tmr.u.timer.expires_ns = rs->state_entry_time +
SHINFO_RACE_TIMEOUT * 1000000000ULL;
vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &tmr);
break;
case 23:
/*
* Optional and possibly repeated sync point.
* Injecting the timer IRQ may fail if the
* shinfo is invalid when the timer expires.
* If the timer has expired but the IRQ hasn't
* been delivered, rearm the timer and retry.
*/
vcpu_ioctl(vcpu, KVM_XEN_VCPU_GET_ATTR, &tmr);
/* Resume the guest if the timer is still pending. */
if (tmr.u.timer.expires_ns)
break;
/* All done if the IRQ was delivered. */
if (!evtchn_irq_expected)
break;
tmr.u.timer.expires_ns = rs->state_entry_time +
SHINFO_RACE_TIMEOUT * 1000000000ULL;
vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &tmr);
break;
case 24:
TEST_ASSERT(!evtchn_irq_expected,
"Expected event channel IRQ but it didn't happen");
ret = pthread_cancel(thread);
TEST_ASSERT(ret == 0, "pthread_cancel() failed: %s", strerror(ret));
ret = pthread_join(thread, 0);
TEST_ASSERT(ret == 0, "pthread_join() failed: %s", strerror(ret));
goto done;
case 0x20: