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b=kSAkat/A4orU1hw1E0qGNnJmOi9HSZhOlS0H2NAs4JHg DWGzj35TUhgJJxAxa0SJvRgvHyo86A1ytAE3Mg6abqmUXK9eRHfcDRK4dbMlTtPs Q6HC8F6TOaJMW2yX3leeKu+nvl4szOnKwiJAe7p1RtPpvu5cKJQTfFYcOkb4neuN YIIiwPZDoZNn2YUCWuyo8EhGfsqJNNeArhMWblzjEmHeTKmPtPSJYEoF7wvsFu84 MI/Y5yc/OO3mQ3bWGlX9YsWDGyQ6ji5QFkhIJVsSqC3yOpc/LKKUUF1kVsKj1VaR og5T+p8KPgn2To+pwdI/3ryhyF3iwF/vOsvDaaAcXA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrvdelgdefiecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvvefukfhfgggtuggjsehgtderredttdejnecuhfhrohhmpeffvghmihcu ofgrrhhivgcuqfgsvghnohhurhcuoeguvghmihesihhnvhhishhisghlvghthhhinhhgsh hlrggsrdgtohhmqeenucggtffrrghtthgvrhhnpeegteelueelleeiheetkeeiueeftedt fefgkeeufeefgeehleeiteejgfejjeevjeenucffohhmrghinhepfhhrvggvuggvshhkth hophdrohhrghenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhr ohhmpeguvghmihesihhnvhhishhisghlvghthhhinhhgshhlrggsrdgtohhm X-ME-Proxy: Feedback-ID: iac594737:Fastmail Date: Mon, 12 Dec 2022 20:31:29 -0500 From: Demi Marie Obenour To: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= Cc: Andrew Cooper , "xen-devel@lists.xenproject.org" , Jan Beulich , Roger Pau Monne , Wei Liu , George Dunlap , "Tim (Xen.org)" , Juergen Gross Subject: Re: [RFC PATCH 8/8] Use Linux's PAT Message-ID: References: <9f0bd911ba6c7fe1b7285f232154d42807145ced.1670300446.git.demi@invisiblethingslab.com> <4b2a87e1-89d1-b5fb-bd92-b891c8cea98a@citrix.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="UWZR7xcu43SLGH1P" Content-Disposition: inline In-Reply-To: --UWZR7xcu43SLGH1P Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Mon, 12 Dec 2022 20:31:29 -0500 From: Demi Marie Obenour To: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= Cc: Andrew Cooper , "xen-devel@lists.xenproject.org" , Jan Beulich , Roger Pau Monne , Wei Liu , George Dunlap , "Tim (Xen.org)" , Juergen Gross Subject: Re: [RFC PATCH 8/8] Use Linux's PAT On Tue, Dec 06, 2022 at 07:12:06PM +0100, Marek Marczykowski-G=C3=B3recki w= rote: > On Tue, Dec 06, 2022 at 01:01:41PM -0500, Demi Marie Obenour wrote: > > On Tue, Dec 06, 2022 at 11:38:03AM +0000, Andrew Cooper wrote: > > > On 06/12/2022 04:33, Demi Marie Obenour wrote: > > > > This is purely for testing, to see if it works around a bug in i915= =2E It > > > > is not intended to be merged. > > > > > > > > NOT-signed-off-by: DO NOT MERGE > > >=20 > > > Following up on Marek's report on IRC/Matrix, you're saying that this > > > change does actually fix screen corruption issues on AlderLake, and > > > something on TigerLake too? > >=20 > > Correct > >=20 > > > If that is actually the case, then one of two things is happening.=C2= =A0 Either, > > >=20 > > > 1) Drivers in Linux are bypassing the regular caching APIs, or > >=20 > > This would not surprise me at all. > >=20 > > > 2) The translation logic between Linux's idea of cacheability and Xen= 's > > > PAT values is buggy. > >=20 > > How could I check for this? >=20 > See Andy's unit test idea on #xendevel: >=20 > as a pretty simple "unit" test in dom0, it might be a good idea to > have a module which watches the PTE in question, and cycles through > various of the memremap_*() APIs and checks the raw PTE that gets > written after Linux and Xen are done fighting with it This confirmed that the translation logic is correct, which means that i195 is buggy. I filed https://gitlab.freedesktop.org/drm/intel/-/issues/7= 648 for that. --=20 Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab --UWZR7xcu43SLGH1P Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEdodNnxM2uiJZBxxxsoi1X/+cIsEFAmOX1fQACgkQsoi1X/+c IsGzwBAApKIVzOPVGQdtmZMqvq8mHF3lSYc02JHR9nnxQpsrKSifDH7hDGd7Bgh4 DeFPZ35/wSXv/A/R4Emdf2cJ2SwDNqa03AuWiI1LZred5/+vPri15KGRKHGcuZ4n zCmORs4FyFCJPpPyvSEcCWQS9qIeLM7ozQrh9wkKKxB8dz1nC1nq/jPSzyTDjEX/ NORcOvLkEAwpwJr0amTYNfxTf6xerG22dqd6NU30xpCzH4nIwvYYEqaMr4CzAvbl F86xw08Wagno2EL3OhSJXQeNmOg7lretTzkNTFv2mU6tgz2XZFiXwEgB4dTmBULI LWgEul3gcsXtB1HxzkkuP9rR6cXniQn2tGgRhNcSAd2x/O9L/j99RCqwUs3Byqai 4EjdR9Dpob36e0tnoFz21jS3ebIhbmossB/S3WEA9NicJMDlmE4QJQEPANgHAW+K 872j1W12yl70DIOZcMC6tJRCrohtIPSgiAhSmMHU4PN85odALmD1TrCLB9HydrRA QgWO6bfhHxynKpmTjVx7GDX+Y1mEMJFIOqRtl2aTrmYPfCoNGwdkxg2EZKfAiYqd tSFWU2tX0+00fV0jJE5UNIHV3Sn20iUfFvAVie8pramqOXIFkF2hGiVW0bGQ9+my DLMMZ3MejbCEEvlz1mgFF0Vv+3WXMsjnAuT76GXAbd/CdPbtlpc= =7fL3 -----END PGP SIGNATURE----- --UWZR7xcu43SLGH1P--