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[80.210.64.78]) by smtp.gmail.com with ESMTPSA id u21sm3431136edl.54.2017.12.14.07.45.23 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Thu, 14 Dec 2017 07:45:23 -0800 (PST) Date: Thu, 14 Dec 2017 16:45:18 +0100 From: Christoffer Dall To: Jia He Subject: Re: [PATCH] KVM: arm/arm64: don't set vtimer->cnt_ctl in kvm_arch_timer_handler Message-ID: <20171214154518.GX910@cbox> References: <1513148407-2611-1-git-send-email-hejianet@gmail.com> <20171213091803.GQ910@cbox> <20171214130954.GV910@cbox> <5615f3e1-756e-0537-f0b6-20ae8626ac87@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5615f3e1-756e-0537-f0b6-20ae8626ac87@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171214_154546_581616_F6F254AD X-CRM114-Status: GOOD ( 36.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marc Zyngier , Jia He , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu, Dec 14, 2017 at 11:28:04PM +0800, Jia He wrote: > > On 12/14/2017 9:09 PM, Christoffer Dall Wrote: > >On Thu, Dec 14, 2017 at 12:57:54PM +0800, Jia He wrote: > >Hi Jia, > > > >>I have tried your newer level-mapped-v7 branch, but bug is still there. > >> > >>There is no special load in both host and guest. The guest (kernel > >>4.14) is often hanging when booting > >> > >>the guest kernel log > >> > >>[ OK ] Reached target Remote File Systems. > >>Starting File System Check on /dev/mapper/fedora-root... > >>[ OK ] Started File System Check on /dev/mapper/fedora-root. > >>Mounting /sysroot... > >>[ 2.670764] SGI XFS with ACLs, security attributes, no debug enabled > >>[ 2.678180] XFS (dm-0): Mounting V5 Filesystem > >>[ 2.740364] XFS (dm-0): Ending clean mount > >>[ OK ] Mounted /sysroot. > >>[ OK ] Reached target Initrd Root File System. > >>Starting Reload Configuration from the Real Root... > >>[ 61.288215] INFO: rcu_sched detected stalls on CPUs/tasks: > >>[ 61.290791] 1-...!: (0 ticks this GP) idle=574/0/0 softirq=5/5 fqs=1 > >>[ 61.293664] (detected by 0, t=6002 jiffies, g=-263, c=-264, q=39760) > >>[ 61.296480] Task dump for CPU 1: > >>[ 61.297938] swapper/1 R running task 0 0 1 0x00000020 > >>[ 61.300643] Call trace: > >>[ 61.301260] __switch_to+0x6c/0x78 > >>[ 61.302095] cpu_number+0x0/0x8 > >>[ 61.302867] rcu_sched kthread starved for 6000 jiffies! > >>g18446744073709551353 c18446744073709551352 f0x0 RCU_GP_WAIT_FQS(3) > >>->state=0x402 ->cpu=1 > >>[ 61.305941] rcu_sched I 0 8 2 0x00000020 > >>[ 61.307250] Call trace: > >>[ 61.307854] __switch_to+0x6c/0x78 > >>[ 61.308693] __schedule+0x268/0x8f0 > >>[ 61.309545] schedule+0x2c/0x88 > >>[ 61.310325] schedule_timeout+0x84/0x3b8 > >>[ 61.311278] rcu_gp_kthread+0x4d4/0x7d8 > >>[ 61.312213] kthread+0x134/0x138 > >>[ 61.313001] ret_from_fork+0x10/0x1c > >> > >>Maybe my previous patch is not perfect enough, thanks for your comments. > >> > >>I digged it futher more, do you think below code logic is possibly > >>problematic? > >> > >> > >>vtimer_save_state           (vtimer->loaded = false, cntv_ctl is 0) > >> > >>kvm_arch_timer_handler        (read cntv_ctl and set vtimer->cnt_ctl = 0) > >> > >>vtimer_restore_state            (write vtimer->cnt_ctl to cntv_ctl, > >>then cntv_ctl will > >> > >>                        be 0 forever) > >> > >> > >>If above analysis is reasonable > >Yes, I think there's something there if the hardware doesn't retire the > >signal fast enough... > > > >>how about below patch? already > >>tested in my arm64 server. > >> > >>diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > >>index f9555b1..ee6dd3f 100644 > >>--- a/virt/kvm/arm/arch_timer.c > >>+++ b/virt/kvm/arm/arch_timer.c > >>@@ -99,7 +99,7 @@ static irqreturn_t kvm_arch_timer_handler(int irq, > >>void *dev_id) > >>         } > >>         vtimer = vcpu_vtimer(vcpu); > >> > >>-       if (!vtimer->irq.level) { > >>+       if (vtimer->loaded && !vtimer->irq.level) { > >>                 vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl); > >>                 if (kvm_timer_irq_can_fire(vtimer)) > >>                         kvm_timer_update_irq(vcpu, true, vtimer); > >> > >There's nothing really wrong with that patch, I just didn't think it > >would be necessary, as we really shouldn't see interrupts if the timer > >is not loaded. Can you confirm that a WARN_ON(!vtimer->loaded) in > >kvm_arch_timer_handler() gives you a splat? > Please see the WARN_ON result (without my patch) > [   72.171706] WARNING: CPU: 24 PID: 1768 at > arch/arm64/kvm/../../../virt/kvm/arm/arch_timer.c:101 > kvm_arch_timer_handler+0xc0/0xc8 > > >Also, could you give the following a try (without your patch): > > > >diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > >index 73d262c4712b..4751255345d1 100644 > >--- a/virt/kvm/arm/arch_timer.c > >+++ b/virt/kvm/arm/arch_timer.c > >@@ -367,6 +367,7 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu) > > /* Disable the virtual timer */ > > write_sysreg_el0(0, cntv_ctl); > >+ isb(); > No luck， the bug is still there > ok, so this is a slightly different approach to what you were trying to do. Can you please give this a try and let me know how it goes? Thanks, -Christoffer diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 73d262c4712b..544ed15fbbb3 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -46,7 +46,7 @@ static const struct kvm_irq_level default_vtimer_irq = { .level = 1, }; -static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx); +static bool kvm_timer_irq_can_fire(u32 cnt_ctl); static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, struct arch_timer_context *timer_ctx); static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx); @@ -94,6 +94,7 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id) { struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id; struct arch_timer_context *vtimer; + u32 cnt_ctl; if (!vcpu) { pr_warn_once("Spurious arch timer IRQ on non-VCPU thread\n"); @@ -101,8 +102,8 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id) } vtimer = vcpu_vtimer(vcpu); - vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl); - if (kvm_timer_irq_can_fire(vtimer)) + cnt_ctl = read_sysreg_el0(cntv_ctl); + if (kvm_timer_irq_can_fire(cnt_ctl)) kvm_timer_update_irq(vcpu, true, vtimer); if (unlikely(!irqchip_in_kernel(vcpu->kvm))) @@ -148,10 +149,10 @@ static u64 kvm_timer_compute_delta(struct arch_timer_context *timer_ctx) return 0; } -static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx) +static bool kvm_timer_irq_can_fire(u32 cnt_ctl) { - return !(timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) && - (timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_ENABLE); + return !(cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) && + (cnt_ctl & ARCH_TIMER_CTRL_ENABLE); } /* @@ -164,10 +165,10 @@ static u64 kvm_timer_earliest_exp(struct kvm_vcpu *vcpu) struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); - if (kvm_timer_irq_can_fire(vtimer)) + if (kvm_timer_irq_can_fire(vtimer->cnt_ctl)) min_virt = kvm_timer_compute_delta(vtimer); - if (kvm_timer_irq_can_fire(ptimer)) + if (kvm_timer_irq_can_fire(ptimer->cnt_ctl)) min_phys = kvm_timer_compute_delta(ptimer); /* If none of timers can fire, then return 0 */ @@ -231,7 +232,7 @@ static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx) { u64 cval, now; - if (!kvm_timer_irq_can_fire(timer_ctx)) + if (!kvm_timer_irq_can_fire(timer_ctx->cnt_ctl)) return false; cval = timer_ctx->cnt_cval; @@ -306,7 +307,7 @@ static void phys_timer_emulate(struct kvm_vcpu *vcpu) * don't need to have a soft timer scheduled for the future. If the * timer cannot fire at all, then we also don't need a soft timer. */ - if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer)) { + if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer->cnt_ctl)) { soft_timer_cancel(&timer->phys_timer, NULL); return; } @@ -367,6 +368,7 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu) /* Disable the virtual timer */ write_sysreg_el0(0, cntv_ctl); + isb(); vtimer->loaded = false; out: @@ -398,7 +400,8 @@ void kvm_timer_schedule(struct kvm_vcpu *vcpu) * If both timers are not capable of raising interrupts (disabled or * masked), then there's no more work for us to do. */ - if (!kvm_timer_irq_can_fire(vtimer) && !kvm_timer_irq_can_fire(ptimer)) + if (!kvm_timer_irq_can_fire(vtimer->cnt_ctl) && + !kvm_timer_irq_can_fire(ptimer->cnt_ctl)) return; /*