From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org, x86@kernel.org
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Wanpeng Li <wanpengli@tencent.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Jim Mattson <jmattson@google.com>,
Vivek Goyal <vgoyal@redhat.com>, Gavin Shan <gshan@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 10/10] KVM: x86: deprecate KVM_ASYNC_PF_SEND_ALWAYS
Date: Thu, 28 May 2020 13:14:00 +0200 [thread overview]
Message-ID: <87zh9s2txj.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <551b75f7-b022-313d-fac4-8b3dd83fe76c@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 25/05/20 16:41, Vitaly Kuznetsov wrote:
>> Concerns were expressed around APF events delivery when CPU is not
>> in user mode (KVM_ASYNC_PF_SEND_ALWAYS), e.g.
>> https://lore.kernel.org/kvm/ed71d0967113a35f670a9625a058b8e6e0b2f104.1583547991.git.luto@kernel.org/
>>
>> 'Page ready' events are already free from '#PF abuse' but 'page not ready'
>> notifications still go through #PF (to be changed in the future). Make the
>> probability of running into issues when APF collides with regular #PF lower
>> by deprecating KVM_ASYNC_PF_SEND_ALWAYS. The feature doesn't seem to be
>> important enough for any particular workload to notice the difference.
>
> This has been disabled already in guest code, but I don't see a
> particular reason to deprecate it in the host too. Supporting it on the
> host is just one line of code; if it's a problem *for the guest*, you
> just don't use KVM_ASYNC_PF_SEND_ALWAYS.
>
> Also, note that #VE will always be delivered to the guest even at CPL0;
> the decision on whether to do sync or async page fault at CPL0 will move
> to the guest, but enabling #VE will probably _require_ the
> KVM_ASYNC_PF_SEND_ALWAYS bit to be set (and KVM_ASYNC_PF_DELIVERY_AS_INT
> as well).
I actually missed the fact that guest side is already disabled (I can
see it now in the queue), feel free to ignore this patch then.
--
Vitaly
next prev parent reply other threads:[~2020-05-28 11:14 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-25 14:41 [PATCH v2 00/10] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 01/10] Revert "KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously" Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 02/10] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info Vitaly Kuznetsov
2020-05-26 18:27 ` Vivek Goyal
2020-05-28 8:42 ` Vitaly Kuznetsov
2020-05-28 10:59 ` Paolo Bonzini
2020-06-03 19:35 ` Vivek Goyal
2020-05-25 14:41 ` [PATCH v2 03/10] KVM: rename kvm_arch_can_inject_async_page_present() to kvm_arch_can_dequeue_async_page_present() Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 04/10] KVM: introduce kvm_read_guest_offset_cached() Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 05/10] KVM: x86: interrupt based APF 'page ready' event delivery Vitaly Kuznetsov
2020-06-09 19:10 ` Vivek Goyal
2020-06-09 20:31 ` Paolo Bonzini
2020-06-10 9:01 ` Vitaly Kuznetsov
2020-06-10 11:34 ` Paolo Bonzini
2020-06-10 12:51 ` Vivek Goyal
2020-05-25 14:41 ` [PATCH v2 06/10] KVM: x86: acknowledgment mechanism for async pf page ready notifications Vitaly Kuznetsov
2020-05-28 11:29 ` Paolo Bonzini
2020-05-28 11:39 ` Vitaly Kuznetsov
2020-05-28 11:44 ` Paolo Bonzini
2020-05-25 14:41 ` [PATCH v2 07/10] KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 08/10] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery Vitaly Kuznetsov
2020-06-10 20:51 ` Vivek Goyal
2020-06-10 21:06 ` Paolo Bonzini
2020-05-25 14:41 ` [PATCH v2 09/10] KVM: x86: drop KVM_PV_REASON_PAGE_READY case from kvm_handle_page_fault() Vitaly Kuznetsov
2020-05-25 14:41 ` [PATCH v2 10/10] KVM: x86: deprecate KVM_ASYNC_PF_SEND_ALWAYS Vitaly Kuznetsov
2020-05-28 11:03 ` Paolo Bonzini
2020-05-28 11:14 ` Vitaly Kuznetsov [this message]
2020-05-28 11:04 ` [PATCH v2 00/10] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Paolo Bonzini
2020-06-04 17:45 ` Vivek Goyal
2020-06-04 17:56 ` Paolo Bonzini
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