linux-kernel - Re: [PATCH 0/8] KVM: xen: update shared_info and vcpu

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 for Android: free password hash cracker in your pocket

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

Message-ID: <bb3ed190771eca5481613abcae05f5f5c3084c47.camel@infradead.org>
Date:   Thu, 14 Sep 2023 11:15:28 +0200
From:   David Woodhouse <dwmw2@...radead.org>
To:     Paul Durrant <paul@....org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Paul Durrant <pdurrant@...zon.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: Re: [PATCH 0/8] KVM: xen: update shared_info and vcpu_info handling

On Thu, 2023-09-14 at 08:49 +0000, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@...zon.com>
> 
> Currently we treat the shared_info page as guest memory and the VMM informs
> KVM of its location using a GFN. However it is not guest memory as such;
> it's an overlay page. So we pointlessly invalidate and re-cache a mapping
> to the *same page* of memory every time the guest requests that shared_info
> be mapped into its address space. Let's avoid doing that by modifying the
> pfncache code to allow activation using a fixed userspace HVA as well as
> a GPA.

Looks sane to me in general; thanks.

The changes to the pfncache ended up being a little bit more than I
originally anticipated when I said you just needed to disable the
GPA→uHVA lookup via memslots which was about 10 lines... but I think
it's still true that it's worth using the pfncache to avoid reproducing
the intricate mmu_notifier invalidations.


Download attachment "smime.p7s" of type "application/pkcs7-signature" (5965 bytes)