linux-kernel - Re: [PATCH RFC 1/6] KVM: fix guest_mode optimization in kvm_make_all_cpus

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 11 Apr 2017 10:37:26 +0100
From:   James Hogan <james.hogan@...tec.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     Radim Krčmář <rkrcmar@...hat.com>,
        <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        Christoffer Dall <cdall@...aro.org>,
        Andrew Jones <drjones@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cornelia.huck@...ibm.com>,
        Paul Mackerras <paulus@...abs.org>
Subject: Re: [PATCH RFC 1/6] KVM: fix guest_mode optimization in
 kvm_make_all_cpus_request()

Hi Paolo,

On Tue, Apr 11, 2017 at 01:25:04PM +0800, Paolo Bonzini wrote:
> On 07/04/2017 05:02, James Hogan wrote:
> > This presumably changes the behaviour on x86, from != OUTSIDE_GUEST_MODE
> > to == IN_GUEST_MODE. so:
> > - you'll no longer get IPIs if its in READING_SHADOW_PAGE_TABLES (which
> >   MIPS also now uses when accessing mappings outside of guest mode and
> >   depends upon to wait until the old mappings are no longer in use).
> 
> This is wrong, the purpose of READING_SHADOW_PAGE_TABLES is "kvm_flush_remote_tlbs
> should send me an IPI, because I want to stop kvm_flush_remote_tlbs until I'm done
> reading the page tables".

That sounds equivalent to what I meant for MIPS, i.e.
kvm_flush_remote_tlbs() does the waiting (not the thing accessing guest
mappings).

Cheers
James

Download attachment "signature.asc" of type "application/pgp-signature" (802 bytes)