linux-kernel - Re: [RFC PATCH 2/2] KVM: arm64: vgic-its: Unmap all vPEs on shutdown

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]

Message-ID: <b0047fa676bf887ef534fa8dff064d32149533a9.camel@infradead.org>
Date: Tue, 22 Jul 2025 12:35:40 +0200
From: David Woodhouse <dwmw2@...radead.org>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
 Zenghui Yu <yuzenghui@...wei.com>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Paolo Bonzini
 <pbonzini@...hat.com>, Sebastian Ott <sebott@...hat.com>, Andre Przywara
 <andre.przywara@....com>, Thorsten Blum <thorsten.blum@...ux.dev>, Shameer
 Kolothum <shameerali.kolothum.thodi@...wei.com>,
 linux-arm-kernel@...ts.infradead.org,  kvmarm@...ts.linux.dev,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: "Saidi, Ali" <alisaidi@...zon.com>
Subject: Re: [RFC PATCH 2/2] KVM: arm64: vgic-its: Unmap all vPEs on shutdown

On Mon, 2025-06-23 at 18:38 +0200, David Woodhouse wrote:
> On Mon, 2025-06-23 at 14:27 +0100, David Woodhouse wrote:
> > From: David Woodhouse <dwmw@...zon.co.uk>
> > 
> > We observed systems going dark on kexec, due to corruption of the new
> > kernel's text (and sometimes the initrd). This was eventually determined
> > to be caused by the vLPI pending tables used by the GIC in the previous
> > kernel, which were not being quiesced properly.
> 
> FWIW this is a previous hack we attempted which *didn't* work. (For
> illustration only; ignore the syscore .kexec hook. We addressed that
> differently in the end with
> https://lore.kernel.org/kexec/20231213064004.2419447-1-jgowans@amazon.com/ )
> 
> At the point where the its_kexec() hook in this patch has completed, we
> poisoned the (ex-) vLPI pending tables and then scanned for corruption
> in them. We saw the same characteristic pattern of corruption which had
> been breaking the next kernel after kexec: 32 bytes copied from offset
> 0 to offset 32 in a page, followed by bytes 0, 1, 32, 33, 34, 35 being
> zeroed.
> 
> Adding a few milliseconds of sleep before the poisoning was enough to
> make the problem go away. As is the patch which calls unmap_all_vpes()
> ∀ kvm.
> 
> Of course, if the GIC were behind an IOMMU as all DMA-capable devices
> should be, this might never have happened...

Any thoughts on this? I'd really appreciate some guidance from Arm on
precisely what is *expected* of the operating system here, to quiesce
the GIC correctly. 

Download attachment "smime.p7s" of type "application/pkcs7-signature" (5069 bytes)