From: Andy Lutomirski <luto@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>, X86 ML <x86@kernel.org>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf page ready notifications
Date: Wed, 29 Apr 2020 17:45:16 -0700 [thread overview]
Message-ID: <CALCETrWQBmmVODuSXac965o29Oxqo6uo4Ujm2AN2FUMztwCnzA@mail.gmail.com> (raw)
In-Reply-To: <0de4a809-e965-d0ad-489f-5b011aa5bf89@redhat.com>
On Wed, Apr 29, 2020 at 10:40 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 29/04/20 19:28, Andy Lutomirski wrote:
> > This seems functional, but I'm wondering if it could a bit simpler and
> > more efficient if the data structure was a normal descriptor ring with
> > the same number slots as whatever the maximum number of waiting pages
> > is. Then there would never need to be any notification from the guest
> > back to the host, since there would always be room for a notification.
>
> No, it would be much more complicated code for a slow path which is
> already order of magnitudes slower than a vmexit. It would also use
> much more memory.
Fair enough.
>
> > It might be even better if a single unified data structure was used
> > for both notifications.
>
> That's a very bad idea since one is synchronous and one is asynchronous.
> Part of the proposal we agreed upon was to keep "page not ready"
> synchronous while making "page ready" an interrupt. The data structure
> for "page not ready" will be #VE.
>
#VE on SVM will be interesting, to say the least, and I think that a
solution that is VMX specific doesn't make much sense. #VE also has
unpleasant issues involving the contexts in which it can occur. You
will have quite a hard time convincing me to ack the addition of a #VE
entry handler for this. I think a brand new vector is the right
solution.
next prev parent reply other threads:[~2020-04-30 0:45 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 9:36 [PATCH RFC 0/6] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Vitaly Kuznetsov
2020-04-29 9:36 ` [PATCH RFC 1/6] Revert "KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously" Vitaly Kuznetsov
2020-05-05 1:22 ` Gavin Shan
2020-05-05 14:16 ` Vivek Goyal
2020-05-06 15:17 ` Vitaly Kuznetsov
2020-05-11 19:17 ` Vivek Goyal
2020-04-29 9:36 ` [PATCH RFC 2/6] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info Vitaly Kuznetsov
2020-05-04 23:52 ` Gavin Shan
2020-05-05 8:08 ` Vitaly Kuznetsov
2020-04-29 9:36 ` [PATCH RFC 3/6] KVM: x86: interrupt based APF page-ready event delivery Vitaly Kuznetsov
2020-04-29 10:54 ` Paolo Bonzini
2020-04-29 12:40 ` Vitaly Kuznetsov
2020-04-29 13:21 ` Paolo Bonzini
2020-04-29 21:27 ` Peter Xu
2020-04-30 8:31 ` Vitaly Kuznetsov
2020-04-30 13:28 ` Peter Xu
2020-04-30 13:49 ` Vitaly Kuznetsov
2020-05-05 15:22 ` Vivek Goyal
2020-04-29 9:36 ` [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf page ready notifications Vitaly Kuznetsov
2020-04-29 17:28 ` Andy Lutomirski
2020-04-29 17:40 ` Paolo Bonzini
2020-04-30 0:45 ` Andy Lutomirski [this message]
2020-04-30 6:46 ` Paolo Bonzini
2020-04-30 6:49 ` Paolo Bonzini
2020-04-30 8:40 ` Vitaly Kuznetsov
2020-04-30 9:27 ` Paolo Bonzini
2020-04-30 11:33 ` Vitaly Kuznetsov
2020-04-30 11:43 ` Paolo Bonzini
2020-05-05 0:36 ` Gavin Shan
2020-05-05 8:16 ` Vitaly Kuznetsov
2020-05-05 8:51 ` Gavin Shan
2020-05-05 9:54 ` Paolo Bonzini
2020-04-29 9:36 ` [PATCH RFC 5/6] KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT Vitaly Kuznetsov
2020-04-29 10:40 ` Peter Zijlstra
2020-04-29 9:36 ` [PATCH RFC 6/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery Vitaly Kuznetsov
2020-04-29 10:53 ` Paolo Bonzini
2020-04-29 12:44 ` Vitaly Kuznetsov
2020-04-29 13:19 ` Paolo Bonzini
2020-04-29 14:34 ` Vitaly Kuznetsov
2020-05-05 18:59 ` Vivek Goyal
2020-05-05 0:42 ` Gavin Shan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CALCETrWQBmmVODuSXac965o29Oxqo6uo4Ujm2AN2FUMztwCnzA@mail.gmail.com \
--to=luto@kernel.org \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jmattson@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=sean.j.christopherson@intel.com \
--cc=tglx@linutronix.de \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).