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b=sRw+vSq2/Q1C4fVGO9dee8tCbZAcgBlP4S/EpuRWPXzvSLATqms +YVGuGobamnSqzEZwZvxO2IYjzhklQj6ZkRX0wf6iKzQCWz9CvhcoTk5Sm9n9w6z JfnYo44Rk5+kjsnkA9g1e+w+BVIxWpB6Dx/auD1p1zTHY3iSGZdFxL1riz3Si6rd dAqd27+25AtFUA3O5jJynpklib7CRlihmSF4jwtMKVrxDW1tVnCEV60VVi2nmc8b 4G1UoahLX3U7lnIcnpGq+X/+TQfRjHENnbAhPFfd5a3KijVT8Wu+Snj/vs0d3VWe qwi8zvsFE0z72r+fWL765E75+GbcFKQHzXw== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefgedrtddtgddukeekuddtucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfurfetoffkrfgpnffqhgenuceu rghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujf gurhepfffhvfevuffkfhggtggujgesghdtreertddtjeenucfhrhhomhepofgrrhgvkhcu ofgrrhgtiiihkhhofihskhhiqdfikphrvggtkhhiuceomhgrrhhmrghrvghksehinhhvih hsihgslhgvthhhihhnghhslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepieeluddv keejueekhfffteegfeeiffefjeejvdeijedvgfejheetuddvkeffudeinecuffhomhgrih hnpehkvghrnhgvlhdrohhrghenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhep mhgrihhlfhhrohhmpehmrghrmhgrrhgvkhesihhnvhhishhisghlvghthhhinhhgshhlrg gsrdgtohhmpdhnsggprhgtphhtthhopedutddpmhhouggvpehsmhhtphhouhhtpdhrtghp thhtohepjhgsvghulhhitghhsehsuhhsvgdrtghomhdprhgtphhtthhopehtvgguugihrd grshhtihgvsehvrghtvghsrdhtvggthhdprhgtphhtthhopegrnhgurhgvfidrtghoohhp vghrfeestghithhrihigrdgtohhmpdhrtghpthhtoheprghnthhhohhnhidrphgvrhgrrh gusehvrghtvghsrdhtvggthhdprhgtphhtthhopehmihgthhgrlhdrohhriigvlhesrghm ugdrtghomhdprhgtphhtthhopehjuhhlihgvnhesgigvnhdrohhrghdprhgtphhtthhope hrohhgvghrrdhprghusegtihhtrhhigidrtghomhdprhgtphhtthhopehsshhtrggsvghl lhhinhhisehkvghrnhgvlhdrohhrghdprhgtphhtthhopeguphhsmhhithhhsegrphgvrh htuhhsshholhhuthhiohhnshdrtghomh X-ME-Proxy: Feedback-ID: i1568416f:Fastmail Date: Fri, 6 Feb 2026 12:52:18 +0100 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: Teddy Astie , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , Roger Pau =?utf-8?B?TW9ubsOp?= , Stefano Stabellini , "Daniel P. Smith" , xen-devel@lists.xenproject.org Subject: Re: [PATCH] efi: Enable EFI_SET_VIRTUAL_ADDRESS_MAP by default Message-ID: References: <82dfede43d81c2072f90b01d12fe5ef18c80fc24.1770312308.git.teddy.astie@vates.tech> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cPD7qH7Wc/gZxncq" Content-Disposition: inline In-Reply-To: --cPD7qH7Wc/gZxncq Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Fri, 6 Feb 2026 12:52:18 +0100 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: Teddy Astie , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , Roger Pau =?utf-8?B?TW9ubsOp?= , Stefano Stabellini , "Daniel P. Smith" , xen-devel@lists.xenproject.org Subject: Re: [PATCH] efi: Enable EFI_SET_VIRTUAL_ADDRESS_MAP by default On Fri, Feb 06, 2026 at 07:29:49AM +0100, Jan Beulich wrote: > On 05.02.2026 18:27, Teddy Astie wrote: > > Many machines fail to boot if this option is disabled, as > > there are no known drawback toggling this option, enable it > > by default. >=20 > "no known drawback" ignores why it wasn't enabled originally. Imo this > wants at least mentioning, if not discussing. Relevant discussion was at https://lore.kernel.org/xen-devel/4e46a667-da69-= 9f25-387e-4dd45db10cda@suse.com/ (previous attempt at switching the default) And also, (large) part of the reason for this being off by default initially was it being close to 4.13 release: https://lore.kernel.org/xen-devel/272a9354-bcb4-50a4-a251-6a453221d6e3@citr= ix.com/ Now it's substantially earlier in the 4.22 release cycle. But yes, some note in patch description would be nice. > > --- a/xen/common/Kconfig > > +++ b/xen/common/Kconfig > > @@ -363,13 +363,14 @@ config KEXEC > > =20 > > config EFI_SET_VIRTUAL_ADDRESS_MAP > > bool "EFI: call SetVirtualAddressMap()" if EXPERT > > + default y > > help > > Call EFI SetVirtualAddressMap() runtime service to setup memory = map for > > further runtime services. According to UEFI spec, it isn't stric= tly > > necessary, but many UEFI implementations misbehave when this cal= l is > > missing. > > =20 > > - If unsure, say N. > > + If unsure, say Y. >=20 > When this was added, it was actually hacked in with the aim of minimal > intrusiveness. When we now default it to on, I wonder if other changes > shouldn't be made (maybe not right in this patch, but perhaps in a > single series). For example, identity mapping (with its implied > restrictions) ought to be possible to do away with when the option is > enabled. Whether the separate EFI page tables would still be needed > also is questionable. This is an interesting question, but IMHO the current approach is safer (or rather: more reliable) - which is relevant given how many UEFI systems are not exactly spec compliant... One approach that could be tried is to mirror what Linux does, but I don't see it as necessary for flipping the default. And in fact I would rather prefer to not do that at the same time - the current approach is battle tested by several downstream projects on a large number of systems. > I further wonder whether the EXPERT dependency of the prompt wouldn't > better be dropped when flipping the default. IMO the EXPERT dependency is still relevant. This option is basically "break Xen on a large number of UEFI systems". --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --cPD7qH7Wc/gZxncq Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmmF1fIACgkQ24/THMrX 1ywpaAf+IdQvew+Tmba3gd8DfFsbt/AqXwj2y9McV+0qoKjZ7VuLLj5Z3L5rY48Q nI/n/5w8Jbanh/uK4/o87ApPxnw4SRKftr3w308s3lQPE/qoxwy7BPpbULaguMV+ yUEO9cQTTPprSsY7qcu58HCWKgWF0jA1x2IA3uKU8WyDdxEdQ7dvJp3FX/xWSzaG W8j1TVAj1XIoisNe8q6aPB9+wtFaecCj9m7eRU0C873ax6y5V+ZbWah6z/GVX118 4QW0JligkgQY5Wb6kJyQ/0O5e8qC24E2nbtVAtx+bfMY4n+4PmUAKgRrcBqM5wst FWNkBl5ASrJR4AgrxPnY3Y32xTk8Hg== =rCxC -----END PGP SIGNATURE----- --cPD7qH7Wc/gZxncq--