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Tue, 03 Aug 2021 13:52:25 +0000 (UTC) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id B31DA5C00E1; Tue, 3 Aug 2021 09:52:25 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Tue, 03 Aug 2021 09:52:25 -0400 Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 3 Aug 2021 09:52:24 -0400 (EDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 25dfe777-96a1-45da-9ac5-5cf27872cf15 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=ltLepX ykxxHhw3LwO+AcN+PFeuahYfjI3GmCX08PcUs=; b=OxobtOMDmPj604kZcSOLO3 b+m7tuwVqZzxg7WETKCdaqWuGYt2TB3wqsMTJIW8SVBIThHj4CnshkhvrO1bQYYn EAn/MD+5sK+gl5vInI8yC0PbQRoJJ+31V7/JOCyEctGlFMkZP4vmydHK6RZ4/Vx7 Be5Cd6GRbm3v6Eq8ne3Vf3dv6nolTItS2jzFNNbeinZKBMfbuJ/pGpoOpnPZpMLF O7k7U+vbwjE1JCdAYZ6MH4IfMV6Bsem2d+mnz3QQcQZJRiXShEhBTtoutPZctOog CQj0UUuch1i1Jh+IE4oKDECjv9/ORttTlFkdQB2q70J5jhcWA3opQExt0JCfUf3Q == X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrieeggdeiiecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvuffkfhggtggujgesghdtroertddtjeenucfhrhhomhepofgrrhgvkhcu ofgrrhgtiiihkhhofihskhhiqdfikphrvggtkhhiuceomhgrrhhmrghrvghksehinhhvih hsihgslhgvthhhihhnghhslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepieeiheej geetgeegiefghfekkeeifeejudehvdffhfeigfekhfdvveefjeffvdefnecuvehluhhsth gvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepmhgrrhhmrghrvghksehi nhhvihhsihgslhgvthhhihhnghhslhgrsgdrtghomh X-ME-Proxy: Date: Tue, 3 Aug 2021 15:52:20 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Kevin Tian , Andrew Cooper Subject: Re: [PATCH] VT-d: Tylersburg errata apply to further steppings Message-ID: References: <07ded368-5c12-c06e-fd94-d7ae52d18836@suse.com> <10425176-438f-370b-9d60-183d6e0f5441@suse.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="yRbA9OzDeI5UJ5Nl" Content-Disposition: inline In-Reply-To: --yRbA9OzDeI5UJ5Nl Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Tue, 3 Aug 2021 15:52:20 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Kevin Tian , Andrew Cooper Subject: Re: [PATCH] VT-d: Tylersburg errata apply to further steppings On Tue, Aug 03, 2021 at 03:44:10PM +0200, Jan Beulich wrote: > On 03.08.2021 15:30, Marek Marczykowski-G=C3=B3recki wrote: > > On Tue, Aug 03, 2021 at 03:16:14PM +0200, Jan Beulich wrote: > >> On 03.08.2021 15:12, Marek Marczykowski-G=C3=B3recki wrote: > >>> On Tue, Aug 03, 2021 at 03:06:50PM +0200, Jan Beulich wrote: > >>>> On 03.08.2021 15:01, Marek Marczykowski-G=C3=B3recki wrote: > >>>>> Ok, then, just setting iommu_intremap=3Dfalse should do the right t= hing, > >>>> > >>>> ... if "iommu=3Dforce" is in use (but not otherwise), ... > >>> > >>> But that's the purpose of iommu=3Dforce, no? > >>> With "iommu=3Dforce": strictly require IOMMU > >>> Without "iommu=3Dforce": use IOMMU on best-effort basis > >>> > >>> It makes sense to refuse the boot if intremap is broken in the first > >>> case. But also, it makes sense to allow using IOMMU without intremp in > >>> the second case. > >> > >> I agree with both statements. What I disagree with is that the latter > >> happens by default (instead of only upon admin override), including > >> the case of intremap being unavailable in the first place. > >=20 > > "upon admin override" - do I read the code right, that iommu=3Dno-intre= map > > will actually achieve this effect? >=20 > In the case of this quirk - yes, as the call to the checking function is > gated by a check of iommu_intremap. But by "admin override" I meant a > per-guest attribute, not a host-wide one that isn't explicitly meant to > cover all guests. >=20 > > Will that allow to use IOMMU without > > interrupt remapping on a hardware where it's broken? In that case, maybe > > at least add this info to the log message? >=20 > You mean to suggest the use of this option? I'd rather not, to be honest. > I don't think options like this should be suggested to be used. I'd > prefer if we had less of such options, i.e. if they went away after some > initial integration phase. Indeed, in fact I agree, this should be per-guest configurable option (and in some cases, it kind of is - toolstack will refuse to boot a=20 domain with PCI devices if IOMMU is missing). But, as you noted earlier, there is no way to require intremap, on per-domain basis (regardless of what the default behavior would be). As for optionally requiring IOMMU host-wide, this still makes sense, as IOMMU could be used not only for PCI passthrough, but also to protect dom0 from some (possibly hot-plugged) devices - using quarantine feature. There may be also some desired interactions with Intel TXT (which AFAIR itself requires working VT-d). --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --yRbA9OzDeI5UJ5Nl Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmEJShQACgkQ24/THMrX 1yw4sgf/YiTQchoSReND5JD2iSCV1ssEQeWCy0Z315lOwTVxwpAZmi5m2o09n9ku iGFKNlayXk5k+rdeDv5DCgUo2cJy6U/mxy2O6f/Gl/8maPxxTJRAb+JYSIDVqGsm bOuLT0Thd7SQt+2OiQhocMmDqUT5nBoiya+FzWPLLthXl8gFQEMKIAe2rOntTqsD 5Pt1JAm0i3yuBbcEdAQCTcXNW31hENUSkSvZsJatU9+bMKL78wR9KXCCTGtK1bX5 9zWO2mIVpV7Ddm0+dQF+syZRkSRN+cdTVcVjvt1hRyoMoRUjfOACNSnPWknNy2Vp By8MmSrlH0EEvFLAFSKLm6QLbZ93vA== =0MRW -----END PGP SIGNATURE----- --yRbA9OzDeI5UJ5Nl--