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b=W0oXX0szqDgdSTeB/KEeZh7Cl2cIze+CyzopAHfap8qN 32R3ImpWrthY81ghneDUHxt/l+imx11Zi/u/2FYTZx2EQRUAwq93fU92+qqoFrSL Zk43bB2tKEzoq42Yp+64gWr+X5ys09o73ALmW2p/y59r0DmZUdOpxN5+poGtaUt4 nFEHL2ZkkL/RKZRIQWbKJINKLa7y7pz7IVeG+43qsbZ8St/TwMOoRI0JIyJ+YSod EI/ekuY4ZalUPN/Yk2FhEUuSZCAfX5Jibu9/ttnC/iVXmdifA8ljOcd6x7uBz4w4 seQ+1rpA3/KreXTETgnUQeJNyViGo8NsTbKvJtOmfw== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrudekuddggeeiucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvfevuffkfhggtggujgesghdtreertddtjeenucfhrhhomhepofgrrhgv khcuofgrrhgtiiihkhhofihskhhiqdfikphrvggtkhhiuceomhgrrhhmrghrvghksehinh hvihhsihgslhgvthhhihhnghhslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepieel uddvkeejueekhfffteegfeeiffefjeejvdeijedvgfejheetuddvkeffudeinecuffhomh grihhnpehkvghrnhgvlhdrohhrghenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgr mhepmhgrihhlfhhrohhmpehmrghrmhgrrhgvkhesihhnvhhishhisghlvghthhhinhhgsh hlrggsrdgtohhm X-ME-Proxy: Feedback-ID: i1568416f:Fastmail Date: Thu, 23 Feb 2023 14:08:13 +0100 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: Demi Marie Obenour , Andrew Cooper , George Dunlap , Julien Grall , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org Subject: Re: [PATCH] Call SetVirtualAddressMap() by default Message-ID: References: <9a0e5021a612951c4174c45099edc8a4fb5bd3bb.1677091168.git.demi@invisiblethingslab.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Qf6HhAtMH2yMFTkg" Content-Disposition: inline In-Reply-To: --Qf6HhAtMH2yMFTkg Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Thu, 23 Feb 2023 14:08:13 +0100 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Jan Beulich Cc: Demi Marie Obenour , Andrew Cooper , George Dunlap , Julien Grall , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org Subject: Re: [PATCH] Call SetVirtualAddressMap() by default On Thu, Feb 23, 2023 at 11:16:28AM +0100, Jan Beulich wrote: > On 22.02.2023 20:14, Demi Marie Obenour wrote: > > To quote Andrew Cooper: > >=20 > >> I know we've had this argument before, but not calling > >> SetVirtualAddressMap() isn't a viable option. It's a prerequisite to > >> function on literally millions of devices > >=20 > > Qubes OS has been shipping EFI_SET_VIRTUAL_ADDRESS_MAP for years, and I > > believe OpenXT and EVE ship it as well. Mark EFI_SET_VIRTUAL_ADDRESS_MAP > > as SUPPORTED and enable it by default. >=20 > This is insufficient justification. The main reason why we don't call > it is because it can be called only once. Any entity taking over later > (e.g. via kexec) can't do anything anymore about the virtual address > associations once set. Hence what's needed to justify a change like > this is an explanation of why this restriction is not really an issue > to anyone in any case. AFAIR from the discussion about the original patch, kexec under Xen does not preserve runtime services working anyway, so this limitation is more about some possible kexec implementation in the future, not actually breaking something right now. And since Linux calls SetVirtualAddressMap() _and_ supports kexec just fine, it's definitely possible to design this future kexec extension to work after SetVirtualAddressMap() too. Relevant parts of that older discussion: - https://lore.kernel.org/all/272a9354-bcb4-50a4-a251-6a453221d6e3@citrix.c= om/T/#u - https://lore.kernel.org/all/20191009235725.GT8065@mail-itl/T/#u --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --Qf6HhAtMH2yMFTkg Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmP3ZTwACgkQ24/THMrX 1yzLBggAlJUX6xnte1Yvtl2HFhnzX/AW+FzB4FV3hWSaJH2gmqurshobv4tCR2qe aRb32CUPiG7PKwWIbBxQfsMsdKMMZb6UJgqyLmeqGCf3ktdWtvfDVVj17bBTXIEo R0cGXexrh2kIUp+41OL/aob0OvOr8RbvjCWGgv0i4/JzL1AV0dL5/vd8Yj4GQDMm 3NRgZCIyl+HptTJBAD4PInI6IQq9TDNnjWnkksfDA3KPoKN70HlJTlTPUtf2MTtT L6A1F1p+C2UX08YpwAAo1TFBkonYVUzNgpzC8T18dWwG2FrSMHhpqDK/4v9ncO9g GLLJN+DyhJk4BSE1H/IvT58ETbfStg== =Vrkm -----END PGP SIGNATURE----- --Qf6HhAtMH2yMFTkg--