From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
kvm list <kvm@vger.kernel.org>, stable <stable@vger.kernel.org>
Subject: Re: [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS
Date: Mon, 09 Mar 2020 20:05:18 +0100 [thread overview]
Message-ID: <87d09l73ip.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrUHwd8pNr_ZdFqY8vMjJeMdNyw2C+FL6uOUM98SEE9rNQ@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
> On Mon, Mar 9, 2020 at 2:09 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>> Paolo Bonzini <pbonzini@redhat.com> writes:
>> > Yes, this works but Andy was not happy about adding more
>> > save-and-restore to NMIs. If you do not want to do that, I'm okay with
>> > disabling async page fault support for now.
>>
>> I'm fine with doing that save/restore dance, but I have no strong
>> opinion either.
>>
>> > Storing the page fault reason in memory was not a good idea. Better
>> > options would be to co-opt the page fault error code (e.g. store the
>> > reason in bits 31:16, mark bits 15:0 with the invalid error code
>> > RSVD=1/P=0), or to use the virtualization exception area.
>>
>> Memory store is not the problem. The real problem is hijacking #PF.
>>
>> If you'd have just used a separate VECTOR_ASYNC_PF then none of these
>> problems would exist at all.
>>
>
> I'm okay with the save/restore dance, I guess. It's just yet more
> entry crud to deal with architecture nastiness, except that this
> nastiness is 100% software and isn't Intel/AMD's fault.
And we can do it in C and don't have to fiddle with it in the ASM
maze.
Thanks,
tglx
next prev parent reply other threads:[~2020-03-09 19:05 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-07 2:26 [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS Andy Lutomirski
2020-03-07 15:03 ` Andy Lutomirski
2020-03-07 15:47 ` Thomas Gleixner
2020-03-07 15:59 ` Andy Lutomirski
2020-03-07 19:01 ` Thomas Gleixner
2020-03-07 19:34 ` Andy Lutomirski
2020-03-08 7:23 ` Thomas Gleixner
2020-03-09 6:57 ` Thomas Gleixner
2020-03-09 8:40 ` Paolo Bonzini
2020-03-09 9:09 ` Thomas Gleixner
2020-03-09 18:14 ` Andy Lutomirski
2020-03-09 19:05 ` Thomas Gleixner [this message]
2020-03-09 20:22 ` Peter Zijlstra
2020-04-06 19:09 ` Vivek Goyal
2020-04-06 20:25 ` Peter Zijlstra
2020-04-06 20:32 ` Andy Lutomirski
2020-04-06 20:42 ` Andy Lutomirski
2020-04-07 17:21 ` Vivek Goyal
2020-04-07 17:38 ` Andy Lutomirski
2020-04-07 20:20 ` Thomas Gleixner
2020-04-07 21:41 ` Andy Lutomirski
2020-04-07 22:07 ` Paolo Bonzini
2020-04-07 22:29 ` Andy Lutomirski
2020-04-08 0:30 ` Paolo Bonzini
2020-05-21 15:55 ` Vivek Goyal
2020-04-07 22:48 ` Thomas Gleixner
2020-04-08 4:48 ` Andy Lutomirski
2020-04-08 9:32 ` Borislav Petkov
2020-04-08 10:12 ` Thomas Gleixner
2020-04-08 18:23 ` Vivek Goyal
2020-04-07 22:49 ` Vivek Goyal
2020-04-08 10:01 ` Borislav Petkov
2020-04-07 22:04 ` Paolo Bonzini
2020-04-07 23:21 ` Thomas Gleixner
2020-04-08 8:23 ` Paolo Bonzini
2020-04-08 13:01 ` Thomas Gleixner
2020-04-08 15:38 ` Peter Zijlstra
2020-04-08 16:41 ` Thomas Gleixner
2020-04-09 9:03 ` Paolo Bonzini
2020-04-08 15:34 ` Sean Christopherson
2020-04-08 16:50 ` Paolo Bonzini
2020-04-08 18:01 ` Thomas Gleixner
2020-04-08 20:34 ` Vivek Goyal
2020-04-08 23:06 ` Thomas Gleixner
2020-04-08 23:14 ` Thomas Gleixner
2020-04-09 4:50 ` Andy Lutomirski
2020-04-09 9:43 ` Paolo Bonzini
2020-04-09 11:36 ` Andrew Cooper
2020-04-09 12:47 ` Paolo Bonzini
2020-04-09 14:13 ` Andrew Cooper
2020-04-09 14:32 ` Paolo Bonzini
2020-04-09 15:03 ` Andy Lutomirski
2020-04-09 15:17 ` Paolo Bonzini
2020-04-09 17:32 ` Andy Lutomirski
2020-04-06 21:32 ` Thomas Gleixner
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