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b=MSg432abCvOWSCFezPjXwBgUcJ5RPLoA4C+RrM/04k64 1oeJ1h/GF9pOwCnfHqFWHGbsS7GT8l74SK514NSvBZETdozsNmZgt2pvnf+VjG3G bsQ0q+onay+hkDKiZD6P/VFDfuphBpN3sqbhkFvieKt4cFqerMHOwvJROer5d7iL 6K9y0yZ2Cpt6koNpV/8128PT8szKXxJ2dM+Z4hS5aSHA+uKXMSgS3oiUFYLoSi9W 8orRNZ5xxrPMp6WyzFS4cWATJXNARcuxIn+r0b4/OkA/ifDBX0RFgx513VDflNYH egCAuPr9/edV9ty+4nSzae4NW6fF49rOwrm2FIetjA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrudeigdduvdelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvfevuffkfhggtggujgesghdtreertddtjeenucfhrhhomhepffgvmhhi ucforghrihgvucfqsggvnhhouhhruceouggvmhhisehinhhvihhsihgslhgvthhhihhngh hslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepvdejteegkefhteduhffgteffgeff gfduvdfghfffieefieekkedtheegteehffelnecuvehluhhsthgvrhfuihiivgeptdenuc frrghrrghmpehmrghilhhfrhhomhepuggvmhhisehinhhvihhsihgslhgvthhhihhnghhs lhgrsgdrtghomh X-ME-Proxy: Feedback-ID: iac594737:Fastmail Date: Tue, 6 Dec 2022 14:47:42 -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="kuuIfO5fhwcHDiCZ" Content-Disposition: inline In-Reply-To: --kuuIfO5fhwcHDiCZ Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Tue, 6 Dec 2022 14:47:42 -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 Which PTEs should I check? --=20 Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab --kuuIfO5fhwcHDiCZ Content-Type: application/pgp-signature; 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