From: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
To: Roger Pau Monne <roger.pau@citrix.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 18:49:47 +0200 [thread overview]
Message-ID: <aftxLNbCYKnLrEXM@mail-itl> (raw)
In-Reply-To: <20260506135514.47310-1-roger.pau@citrix.com>
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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...
--
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
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next prev parent reply other threads:[~2026-05-06 16:50 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 ` Marek Marczykowski-Górecki [this message]
2026-05-06 16:55 ` [PATCH v2 0/2] iommu/amd-vi: remove zeroing of " Roger Pau Monné
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