From: Demi Marie Obenour <demi@invisiblethingslab.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: "Juergen Gross" <jgross@suse.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Kees Cook" <keescook@chromium.org>,
"Anton Vorontsov" <anton@enomsg.org>,
"Colin Cross" <ccross@android.com>,
"Tony Luck" <tony.luck@intel.com>,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
linux-efi@vger.kernel.org
Subject: Re: [PATCH v4 2/2] Support ESRT in Xen dom0
Date: Fri, 30 Sep 2022 14:21:22 -0400 [thread overview]
Message-ID: <YzczpIYop5olD4hj@itl-email> (raw)
In-Reply-To: <CAMj1kXEs-o8jvNqRiW+Ue2i52RBgg4iktg8UONCACk8-Gx4XXA@mail.gmail.com>
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On Fri, Sep 30, 2022 at 06:36:11PM +0200, Ard Biesheuvel wrote:
> On Fri, 30 Sept 2022 at 01:02, Demi Marie Obenour
> <demi@invisiblethingslab.com> wrote:
> >
> > fwupd requires access to the EFI System Resource Table (ESRT) to
> > discover which firmware can be updated by the OS. Currently, Linux does
> > not expose the ESRT when running as a Xen dom0. Therefore, it is not
> > possible to use fwupd in a Xen dom0, which is a serious problem for e.g.
> > Qubes OS.
> >
> > Before Xen 4.17, this was not fixable due to hypervisor limitations.
> > The UEFI specification requires the ESRT to be in EfiBootServicesData
> > memory, which Xen will use for whatever purposes it likes. Therefore,
> > Linux cannot safely access the ESRT, as Xen may have overwritten it.
> >
> > Starting with Xen 4.17, Xen checks if the ESRT is in EfiBootServicesData
> > or EfiRuntimeServicesData memory. If the ESRT is in EfiBootServicesData
> > memory, Xen replaces the ESRT with a copy in memory that it has
> > reserved. Such memory is currently of type EFI_RUNTIME_SERVICES_DATA,
> > but in the future it will be of type EFI_ACPI_RECLAIM_MEMORY. This
> > ensures that the ESRT can safely be accessed by the OS.
> >
> > When running as a Xen dom0, use the new
> > xen_config_table_memory_region_max() function to determine if Xen has
> > reserved the ESRT and, if so, find the end of the memory region
> > containing it. This allows programs such as fwupd which require the
> > ESRT to run under Xen, and so makes fwupd support in Qubes OS possible.
> >
> > Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
>
> Why do we need this patch? I'd expect esrt_table_exists() to return
> false when patch 1/2 is applied.
efi_enabled(EFI_MEMMAP) is false under Xen, so there needs to be an
alternative way to get the end of the memory region containing the ESRT.
That is what this patch provides.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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next prev parent reply other threads:[~2022-09-30 18:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-29 23:02 [PATCH v4 0/2] EFI improvements for Xen dom0 Demi Marie Obenour
2022-09-29 23:02 ` [PATCH v4 1/2] Avoid using EFI tables Xen may have clobbered Demi Marie Obenour
2022-09-30 6:44 ` Jan Beulich
2022-09-30 16:30 ` Ard Biesheuvel
2022-09-30 17:11 ` Demi Marie Obenour
2022-09-30 18:27 ` Ard Biesheuvel
2022-09-30 18:50 ` Demi Marie Obenour
2022-10-01 0:30 ` Demi Marie Obenour
2022-10-04 8:22 ` Jan Beulich
2022-10-04 15:46 ` Demi Marie Obenour
2022-10-05 6:15 ` Jan Beulich
2022-10-05 18:11 ` Demi Marie Obenour
2022-10-05 21:28 ` Ard Biesheuvel
2022-10-06 1:40 ` Demi Marie Obenour
2022-10-06 7:31 ` Ard Biesheuvel
2022-10-06 14:43 ` Demi Marie Obenour
2022-10-06 16:19 ` Ard Biesheuvel
2022-10-06 17:22 ` Demi Marie Obenour
2022-10-06 17:56 ` Ard Biesheuvel
2022-10-06 9:22 ` Jan Beulich
2022-09-30 16:38 ` Demi Marie Obenour
2022-09-30 16:25 ` Ard Biesheuvel
2022-09-30 18:15 ` Demi Marie Obenour
2022-09-30 18:42 ` Ard Biesheuvel
2022-09-30 19:00 ` Demi Marie Obenour
2022-09-29 23:02 ` [PATCH v4 2/2] Support ESRT in Xen dom0 Demi Marie Obenour
2022-09-30 16:36 ` Ard Biesheuvel
2022-09-30 18:21 ` Demi Marie Obenour [this message]
2022-09-30 19:11 ` Ard Biesheuvel
2022-09-30 20:20 ` Demi Marie Obenour
2022-09-30 20:59 ` Ard Biesheuvel
2022-09-30 21:24 ` Ard Biesheuvel
2022-09-30 22:22 ` Demi Marie Obenour
2022-09-30 22:25 ` Demi Marie Obenour
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