Re: [PATCH v3 1/2] LoongArch: KVM: Reload one-shot TVAL on migration destination
From: Bibo Mao
Date: Thu Jul 16 2026 - 02:14:34 EST
On 2026/7/15 下午6:06, Tao Cui wrote:
From: Tao Cui <cuitao@xxxxxxxxxx>Reviewed-by: Bibo Mao <maobibo@xxxxxxxxxxx>
kvm_restore_timer() rebuilds the remaining timer countdown from
vcpu->arch.expire, which is host-internal and is not part of the migrated
vCPU state. On the migration destination it is still 0, so for a one-shot
timer that has not expired yet the computed delta is 0 and
write_gcsr_timertick(0) injects the timer interrupt immediately instead of
after the remaining time.
The expired one-shot case (TVAL = -1) is already handled earlier. When
expire has not been set (i.e. on the migration destination), reload the
remaining countdown from the migrated TVAL. This covers both one-shot and
periodic timers. The regular preempt/resume path on the source, where
expire is valid, is unchanged.
Suggested-by: Bibo Mao <maobibo@xxxxxxxxxxx>
Fixes: a5857b9ff6e0 ("LoongArch: KVM: Implement vcpu timer operations")
Signed-off-by: Tao Cui <cuitao@xxxxxxxxxx>
---
arch/loongarch/kvm/timer.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/loongarch/kvm/timer.c b/arch/loongarch/kvm/timer.c
index 3829f35a4070..96f33e34855a 100644
--- a/arch/loongarch/kvm/timer.c
+++ b/arch/loongarch/kvm/timer.c
@@ -119,6 +119,18 @@ void kvm_restore_timer(struct kvm_vcpu *vcpu)
delta = 0;
now = ktime_get();
expire = vcpu->arch.expire;
+ if (!expire) {
+ /*
+ * vcpu->arch.expire is host-internal and is not migrated,
+ * so it is 0 after migration. Reload the remaining countdown
+ * from the migrated TVAL. This covers both one-shot and
+ * periodic timers.
+ */
+ if (ticks < cfg)
+ delta = tick_to_ns(vcpu, ticks);
+ expire = ktime_add_ns(now, delta);
+ }
+
if (ktime_before(now, expire))
delta = ktime_to_tick(vcpu, ktime_sub(expire, now));
else if (cfg & CSR_TCFG_PERIOD) {