From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1957C04AB6 for ; Tue, 28 May 2019 13:12:22 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 6CD382075B for ; Tue, 28 May 2019 13:12:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CD382075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E66D84A4F0; Tue, 28 May 2019 09:12:21 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NYffUrPra+g2; Tue, 28 May 2019 09:12:20 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 84A434A4A9; Tue, 28 May 2019 09:12:20 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 77F534A4A3 for ; Tue, 28 May 2019 09:12:19 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OmU7Mci9LHMQ for ; Tue, 28 May 2019 09:12:18 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E0FC34A331 for ; Tue, 28 May 2019 09:12:17 -0400 (EDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5EF1980D; Tue, 28 May 2019 06:12:17 -0700 (PDT) Received: from localhost (e113682-lin.copenhagen.arm.com [10.32.144.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C3E673F5AF; Tue, 28 May 2019 06:12:16 -0700 (PDT) Date: Tue, 28 May 2019 15:12:15 +0200 From: Christoffer Dall To: Marc Zyngier Subject: Re: [PATCH] KVM: arm/arm64: fix emulated ptimer irq injection Message-ID: <20190528131215.GB6775@e113682-lin.lund.arm.com> References: <20190527114619.16252-1-drjones@redhat.com> <20190528110152.GA6775@e113682-lin.lund.arm.com> <3f9d398b-3be2-5988-d3f9-01b28c4ccb1c@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <3f9d398b-3be2-5988-d3f9-01b28c4ccb1c@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Cc: kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, May 28, 2019 at 01:25:52PM +0100, Marc Zyngier wrote: > On 28/05/2019 12:01, Christoffer Dall wrote: > > On Mon, May 27, 2019 at 01:46:19PM +0200, Andrew Jones wrote: > >> The emulated ptimer needs to track the level changes, otherwise the > >> the interrupt will never get deasserted, resulting in the guest getting > >> stuck in an interrupt storm if it enables ptimer interrupts. This was > >> found with kvm-unit-tests; the ptimer tests hung as soon as interrupts > >> were enabled. Typical Linux guests don't have a problem as they prefer > >> using the virtual timer. > >> > >> Fixes: bee038a674875 ("KVM: arm/arm64: Rework the timer code to use a timer_map") > >> Signed-off-by: Andrew Jones > >> --- > >> virt/kvm/arm/arch_timer.c | 7 ++++++- > >> 1 file changed, 6 insertions(+), 1 deletion(-) > >> > >> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > >> index 7fc272ecae16..9f5d8cc8b5e5 100644 > >> --- a/virt/kvm/arm/arch_timer.c > >> +++ b/virt/kvm/arm/arch_timer.c > >> @@ -324,10 +324,15 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, > >> static void timer_emulate(struct arch_timer_context *ctx) > >> { > >> bool should_fire = kvm_timer_should_fire(ctx); > >> + struct timer_map map; > >> + > >> + get_timer_map(ctx->vcpu, &map); > >> > >> trace_kvm_timer_emulate(ctx, should_fire); > >> > >> - if (should_fire) { > >> + if (ctx == map.emul_ptimer && should_fire != ctx->irq.level) { > >> + kvm_timer_update_irq(ctx->vcpu, !ctx->irq.level, ctx); > >> + } else if (should_fire) { > >> kvm_timer_update_irq(ctx->vcpu, true, ctx); > >> return; > >> } > > > > Hmm, this doesn't feel completely right. > > > > Lowering the line of an emulated timer should only ever happen when the > > guest (or user space) writes to one of the system registers for that > > timer, which should be trapped and that should cause an update of the > > line. > > > > Are we missing a call to kvm_timer_update_irq() from > > kvm_arm_timer_set_reg() ? > > Which is exactly what we removed in 6bc210003dff, for good reasons. > Ah well, I can be wrong twice. Or even three times. > Looking at kvm_arm_timer_write_sysreg(), we end-up calling kvm_timer_vcpu_load, but not updating the irq status. > > How about something like this instead (untested): > > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > index 7fc272ecae16..6a418dcc5433 100644 > --- a/virt/kvm/arm/arch_timer.c > +++ b/virt/kvm/arm/arch_timer.c > @@ -882,10 +882,14 @@ void kvm_arm_timer_write_sysreg(struct kvm_vcpu *vcpu, > enum kvm_arch_timer_regs treg, > u64 val) > { > + struct arch_timer_context *timer; > + > preempt_disable(); > kvm_timer_vcpu_put(vcpu); > > - kvm_arm_timer_write(vcpu, vcpu_get_timer(vcpu, tmr), treg, val); > + timer = vcpu_get_timer(vcpu, tmr); > + kvm_arm_timer_write(vcpu, timer, treg, val); > + kvm_timer_update_irq(vcpu, kvm_timer_should_fire(timer), timer); > > kvm_timer_vcpu_load(vcpu); > preempt_enable(); > Yes, that looks reasonable. Basically, in 6bc210003dff we should have only removed the call to timer_emulate, and not messed around with kvm_timer_update_irq()? After this patch, we'll have moved the call to kvm_timer_update_irq() from kvm_arm_timer_set_reg() to kvm_arm_timer_write_sysreg(). I can't seem to decide if clearly belongs in one place or the other. Thanks, Christoffer _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm