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micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="j8Y+pyk47lYf6y1a" Content-Disposition: inline In-Reply-To: <20260506135514.47310-1-roger.pau@citrix.com> X-purgate-ID: tlsNG-d62444/1778086194-AD5AFFF4-42852402/0/0 X-purgate-type: clean X-purgate-size: 1949 --j8Y+pyk47lYf6y1a Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Wed, 6 May 2026 18:49:47 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Roger Pau Monne Cc: xen-devel@lists.xenproject.org, Jan Beulich , Andrew Cooper , Jason Andryuk , Teddy Astie Subject: Re: [PATCH v2 0/2] iommu/amd-vi: remove zeroing of MMIO region On Wed, May 06, 2026 at 03:55:12PM +0200, Roger Pau Monne wrote: > Hello, >=20 > 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. >=20 > 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... --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --j8Y+pyk47lYf6y1a Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmn7cSwACgkQ24/THMrX 1yyZxQf8CUJvMP7I1sv1PMxXjTsfAkxSupuMPirems1yZ7ya/Qq6eUBU5MSAVO6E 1INLuyh3xsdiXHkVWZEN58ugv/G7S00FrBcjQs0qjZlYRgLdkZJGtBsDEyszbHzW x3y8STslRt7A6091KHjQwfbUK2ft0tOJVcxQRGipIhQYyDyQh1CRE4FWFgHEGiDc P6+jF3guzNBskqtnt2dUQL2YxGH7wh4Os6oDEIwqDMlozH1eQP2SPSTU1w3sgi+r QOlGHAjrMwLtKR/+YzagBuImky9XAmkbWRX4thHiWIDNSp/h4qq8JanlUdATBgd4 ul18mLA1eUVeYh6JrAO8x2KqY5Hz6w== =6TDJ -----END PGP SIGNATURE----- --j8Y+pyk47lYf6y1a--