From: "Roger Pau Monné" <roger.pau@citrix.com>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: xen-devel@lists.xenproject.org, Jan Beulich <jbeulich@suse.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Jason Andryuk <jason.andryuk@amd.com>,
Teddy Astie <teddy.astie@vates.tech>
Subject: Re: [PATCH v2 0/2] iommu/amd-vi: remove zeroing of MMIO region
Date: Wed, 6 May 2026 18:55:19 +0200 [thread overview]
Message-ID: <aftydxyqHXaaZqBx@macbook.local> (raw)
In-Reply-To: <aftxLNbCYKnLrEXM@mail-itl>
On Wed, May 06, 2026 at 06:49:47PM +0200, Marek Marczykowski-Górecki wrote:
> On Wed, May 06, 2026 at 03:55:12PM +0200, Roger Pau Monne wrote:
> > Hello,
> >
> > Unconditionally zeroing the whole IOMMU MMIO region is dangerous, at
> > least on an upcoming platform this does put the IOMMU in a broken state
> > that's not recoverable by the init procedure in Xen.
> >
> > Get rid of the zeroing, and instead attempt to disable the IOMMU ahead
> > of enabling it.
>
> Just to mention it here, while this looks like a step in the right
> direction, even better would be to not disable IOMMU at boot, but
> reconfigure it - to preserve uninterrupted protection when boot time DMA
> protection is enabled in firmware. But that's definitely more work...
Yes, we are aware of this. But IMO booting with the IOMMU enabled
will be a new feature, this is strictly a fix that we can "safely"
backport to stable branches to deal with broken hardware.
Thanks, Roger.
prev parent reply other threads:[~2026-05-06 16:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-06 13:55 [PATCH v2 0/2] iommu/amd-vi: remove zeroing of MMIO region Roger Pau Monne
2026-05-06 13:55 ` [PATCH v2 1/2] iommu/amd-vi: allow disable_iommu() against non-initialized IOMMUs Roger Pau Monne
2026-05-06 13:55 ` [PATCH v2 2/2] iommu/amd-vi: do not zero IOMMU MMIO region Roger Pau Monne
2026-05-06 16:18 ` Andrew Cooper
2026-05-06 16:31 ` Roger Pau Monné
2026-05-07 7:57 ` Jan Beulich
2026-05-06 16:49 ` [PATCH v2 0/2] iommu/amd-vi: remove zeroing of " Marek Marczykowski-Górecki
2026-05-06 16:55 ` Roger Pau Monné [this message]
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