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Date: Tue, 19 Jan 2021 09:27:13 +0800 From: Wanpeng Li <kernellwp@...il.com> To: Sean Christopherson <seanjc@...gle.com> Cc: Nitesh Narayan Lal <nitesh@...hat.com>, LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>, w90p710@...il.com, Paolo Bonzini <pbonzini@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH] Revert "KVM: x86: Unconditionally enable irqs in guest context" On Fri, 15 Jan 2021 at 11:20, Wanpeng Li <kernellwp@...il.com> wrote: > > On Wed, 6 Jan 2021 at 08:51, Sean Christopherson <seanjc@...gle.com> wrote: > > > > +tglx > > > > On Tue, Jan 05, 2021, Nitesh Narayan Lal wrote: > > > This reverts commit d7a08882a0a4b4e176691331ee3f492996579534. > > > > > > After the introduction of the patch: > > > > > > 87fa7f3e9: x86/kvm: Move context tracking where it belongs > > > > > > since we have moved guest_exit_irqoff closer to the VM-Exit, explicit > > > enabling of irqs to process pending interrupts should not be required > > > within vcpu_enter_guest anymore. > > > > Ugh, except that commit completely broke tick-based accounting, on both Intel > > and AMD. With guest_exit_irqoff() being called immediately after VM-Exit, any > > tick that happens after IRQs are disabled will be accounted to the host. E.g. > > on Intel, even an IRQ VM-Exit that has already been acked by the CPU isn't > > processed until kvm_x86_ops.handle_exit_irqoff(), well after PF_VCPU has been > > cleared. > > > > This issue can be 100% reproduced. > https://bugzilla.kernel.org/show_bug.cgi?id=204177 Sorry, the posted link should be https://bugzilla.kernel.org/show_bug.cgi?id=209831 Wanpeng
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