From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Quan Xu <quan.xu0@gmail.com>
Cc: pbonzini@redhat.com, rkrcmar@redhat.com, yang.zhang.wz@gmail.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Luo <bn0418@gmail.com>
Subject: Re: [PATCH RFC 3/7] KVM: timer: synchronize tsc-deadline timestamp for guest
Date: Fri, 8 Dec 2017 10:06:19 -0500 [thread overview]
Message-ID: <20171208150618.GD12069@x230.dumpdata.com> (raw)
In-Reply-To: <1512722390-3654-4-git-send-email-quan.xu0@gmail.com>
On Fri, Dec 08, 2017 at 04:39:46PM +0800, Quan Xu wrote:
> From: Ben Luo <bn0418@gmail.com>
>
> In general, KVM guest programs tsc-deadline timestamp to
> MSR_IA32_TSC_DEADLINE MSR. This will cause a VM-exit, and
> then KVM handles this timer for guest.
>
> The tsc-deadline timestamp is mostly recorded in share page
> with less VM-exit. We Introduce a periodically working kthread
> to scan share page and synchronize timer setting for guest
> on a dedicated CPU.
That sounds like a race. Meaning the guest may put too small window
and this 'working thread to scan' may not get to it fast enough?
Meaning we miss the deadline to inject the timer in the guest.
Or is this part of this PV MSR semantics - that it will only work
for certain amount of values and anything less than say 1ms
should not use the PV MSR?
next prev parent reply other threads:[~2017-12-08 15:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-08 8:39 [PATCH RFC 0/7] kvm pvtimer Quan Xu
2017-12-08 8:39 ` [PATCH RFC 1/7] kvm: x86: emulate MSR_KVM_PV_TIMER_EN MSR Quan Xu
2017-12-08 8:39 ` [PATCH RFC 2/7] kvm: x86: add a function to exchange value Quan Xu
2017-12-08 8:39 ` [PATCH RFC 3/7] KVM: timer: synchronize tsc-deadline timestamp for guest Quan Xu
2017-12-08 15:06 ` Konrad Rzeszutek Wilk [this message]
2017-12-14 1:54 ` Quan Xu
2017-12-08 8:39 ` [PATCH RFC 4/7] KVM: timer: program timer to a dedicated CPU Quan Xu
2017-12-08 8:39 ` [PATCH RFC 5/7] KVM: timer: ignore timer migration if pvtimer is enabled Quan Xu
2017-12-08 8:39 ` [PATCH RFC 6/7] Doc/KVM: introduce a new cpuid bit for kvm pvtimer Quan Xu
2017-12-08 8:39 ` [PATCH RFC 7/7] kvm: guest: reprogram guest timer Quan Xu
2017-12-08 15:10 ` [PATCH RFC 0/7] kvm pvtimer Konrad Rzeszutek Wilk
[not found] ` <CAFv8KnF1Re7Zn2LVvqh=Sr8MmaWJJwZBB1i5ws03GvPVKXRjzA@mail.gmail.com>
2017-12-13 16:28 ` Konrad Rzeszutek Wilk
2017-12-14 2:32 ` Quan Xu
2017-12-14 11:56 ` Paolo Bonzini
2017-12-14 12:06 ` Quan Xu
2017-12-14 13:00 ` Paolo Bonzini
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