[PATCH v3 08/28] i386/xen: Ignore VCPU_SSHOTTMR_future flag in set_singleshot_timer()

David Woodhouse
2023-10-25T14:51:50Z

From: David Woodhouse <dwmw@amazon.co.uk>

Upstream Xen now ignores this flag¹, since the only guest kernel ever to
use it was buggy.

¹ https://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=19c6cbd909

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
target/i386/kvm/xen-emu.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 75b2c557b9..1dc9ab0d91 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -1077,17 +1077,13 @@ static int vcpuop_stop_periodic_timer(CPUState *target)
* Must always be called with xen_timers_lock held.
*/
static int do_set_singleshot_timer(CPUState *cs, uint64_t timeout_abs,
- bool future, bool linux_wa)
+ bool linux_wa)
{
CPUX86State *env = &X86_CPU(cs)->env;
int64_t now = kvm_get_current_ns();
int64_t qemu_now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
int64_t delta = timeout_abs - now;

- if (future && timeout_abs < now) {
- return -ETIME;
- }
-
if (linux_wa && unlikely((int64_t)timeout_abs < 0 ||
(delta > 0 && (uint32_t)(delta >> 50) != 0))) {
/*
@@ -1129,9 +1125,13 @@ static int vcpuop_set_singleshot_timer(CPUState *cs, uint64_t arg)
}

QEMU_LOCK_GUARD(&X86_CPU(cs)->env.xen_timers_lock);
- return do_set_singleshot_timer(cs, sst.timeout_abs_ns,
- !!(sst.flags & VCPU_SSHOTTMR_future),
- false);
+
+ /*
+ * We ignore the VCPU_SSHOTTMR_future flag, just as Xen now does.
+ * The only guest that ever used it, got it wrong.
+ * https://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=19c6cbd909
+ */
+ return do_set_singleshot_timer(cs, sst.timeout_abs_ns, false);
}

static int vcpuop_stop_singleshot_timer(CPUState *cs)
@@ -1156,7 +1156,7 @@ static bool kvm_xen_hcall_set_timer_op(struct kvm_xen_exit *exit, X86CPU *cpu,
err = vcpuop_stop_singleshot_timer(CPU(cpu));
} else {
QEMU_LOCK_GUARD(&X86_CPU(cpu)->env.xen_timers_lock);
- err = do_set_singleshot_timer(CPU(cpu), timeout, false, true);
+ err = do_set_singleshot_timer(CPU(cpu), timeout, true);
}
exit->u.hcall.result = err;
return true;
@@ -1844,7 +1844,7 @@ int kvm_put_xen_state(CPUState *cs)
QEMU_LOCK_GUARD(&env->xen_timers_lock);
if (env->xen_singleshot_timer_ns) {
ret = do_set_singleshot_timer(cs, env->xen_singleshot_timer_ns,
- false, false);
+ false);
if (ret < 0) {
return ret;
}
--
2.40.1