| Message ID | 20230210142711.1177212-1-rkanwal@rivosinc.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v2,1/1] riscv/kvm: Fix VM hang in case of timer delta being zero. | expand |
On Fri, Feb 10, 2023 at 6:27 AM Rajnesh Kanwal <rkanwal@rivosinc.com> wrote: > > In case when VCPU is blocked due to WFI, we schedule the timer > from `kvm_riscv_vcpu_timer_blocking()` to keep timer interrupt > ticking. > > But in case when delta_ns comes to be zero, we never schedule > the timer and VCPU keeps sleeping indefinitely until any activity > is done with VM console. > > This is easily reproduce-able using kvmtool. > ./lkvm-static run -c1 --console virtio -p "earlycon root=/dev/vda" \ > -k ./Image -d rootfs.ext4 > > Also, just add a print in kvm_riscv_vcpu_vstimer_expired() to > check the interrupt delivery and run `top` or similar auto-upating > cmd from guest. Within sometime one can notice that print from > timer expiry routine stops and the `top` cmd output will stop > updating. > > This change fixes this by making sure we schedule the timer even > with delta_ns being zero to bring the VCPU out of sleep immediately. > > Fixes: 8f5cb44b1bae ("RISC-V: KVM: Support sstc extension") > Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com> > --- > v2: Added Fixes tag in commit message. > > v1: https://lore.kernel.org/all/20230210135136.1115213-1-rkanwal@rivosinc.com/ > > arch/riscv/kvm/vcpu_timer.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c > index ad34519c8a13..3ac2ff6a65da 100644 > --- a/arch/riscv/kvm/vcpu_timer.c > +++ b/arch/riscv/kvm/vcpu_timer.c > @@ -147,10 +147,8 @@ static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu) > return; > > delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t); > - if (delta_ns) { > - hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); > - t->next_set = true; > - } > + hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); > + t->next_set = true; > } > > static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu) > -- > 2.25.1 > Reviewed-by: Atish Patra <atishp@rivosinc.com>
On Fri, Feb 10, 2023 at 7:57 PM Rajnesh Kanwal <rkanwal@rivosinc.com> wrote: > > In case when VCPU is blocked due to WFI, we schedule the timer > from `kvm_riscv_vcpu_timer_blocking()` to keep timer interrupt > ticking. > > But in case when delta_ns comes to be zero, we never schedule > the timer and VCPU keeps sleeping indefinitely until any activity > is done with VM console. > > This is easily reproduce-able using kvmtool. > ./lkvm-static run -c1 --console virtio -p "earlycon root=/dev/vda" \ > -k ./Image -d rootfs.ext4 > > Also, just add a print in kvm_riscv_vcpu_vstimer_expired() to > check the interrupt delivery and run `top` or similar auto-upating > cmd from guest. Within sometime one can notice that print from > timer expiry routine stops and the `top` cmd output will stop > updating. > > This change fixes this by making sure we schedule the timer even > with delta_ns being zero to bring the VCPU out of sleep immediately. > > Fixes: 8f5cb44b1bae ("RISC-V: KVM: Support sstc extension") > Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com> Queued this patch for Linux-6.3 fixes. Thanks, Anup > --- > v2: Added Fixes tag in commit message. > > v1: https://lore.kernel.org/all/20230210135136.1115213-1-rkanwal@rivosinc.com/ > > arch/riscv/kvm/vcpu_timer.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c > index ad34519c8a13..3ac2ff6a65da 100644 > --- a/arch/riscv/kvm/vcpu_timer.c > +++ b/arch/riscv/kvm/vcpu_timer.c > @@ -147,10 +147,8 @@ static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu) > return; > > delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t); > - if (delta_ns) { > - hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); > - t->next_set = true; > - } > + hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); > + t->next_set = true; > } > > static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu) > -- > 2.25.1 > > > -- > kvm-riscv mailing list > kvm-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kvm-riscv
diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c index ad34519c8a13..3ac2ff6a65da 100644 --- a/arch/riscv/kvm/vcpu_timer.c +++ b/arch/riscv/kvm/vcpu_timer.c @@ -147,10 +147,8 @@ static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu) return; delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t); - if (delta_ns) { - hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); - t->next_set = true; - } + hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL); + t->next_set = true; } static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu)
In case when VCPU is blocked due to WFI, we schedule the timer from `kvm_riscv_vcpu_timer_blocking()` to keep timer interrupt ticking. But in case when delta_ns comes to be zero, we never schedule the timer and VCPU keeps sleeping indefinitely until any activity is done with VM console. This is easily reproduce-able using kvmtool. ./lkvm-static run -c1 --console virtio -p "earlycon root=/dev/vda" \ -k ./Image -d rootfs.ext4 Also, just add a print in kvm_riscv_vcpu_vstimer_expired() to check the interrupt delivery and run `top` or similar auto-upating cmd from guest. Within sometime one can notice that print from timer expiry routine stops and the `top` cmd output will stop updating. This change fixes this by making sure we schedule the timer even with delta_ns being zero to bring the VCPU out of sleep immediately. Fixes: 8f5cb44b1bae ("RISC-V: KVM: Support sstc extension") Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com> --- v2: Added Fixes tag in commit message. v1: https://lore.kernel.org/all/20230210135136.1115213-1-rkanwal@rivosinc.com/ arch/riscv/kvm/vcpu_timer.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)