From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Lennart Poettering <mzxreary@0pointer.de>,
Ard Biesheuvel <ardb@kernel.org>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Mikko Rapeli <mikko.rapeli@linaro.org>,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-integrity@vger.kernel.org
Subject: Re: [PATCH] efi: expose TPM event log to userspace via sysfs
Date: Thu, 25 Apr 2024 09:24:48 -0400 [thread overview]
Message-ID: <f6259f0a28b80db78d28475105ae7f37655a58ee.camel@HansenPartnership.com> (raw)
In-Reply-To: <ZiopXE6-AucAB9NM@gardel-login>
On Thu, 2024-04-25 at 11:58 +0200, Lennart Poettering wrote:
[...]
> General purpose distros typically don't build all TPM drivers into
> the kernel, but ship some in the initrd instead. Then, udev is
> responsible for iterating all buses/devices and auto-loading the
> necessary drivers. Each loaded bus driver might make more devices
> available for which more drivers then need to be loaded, and so on.
> Some of the busses are "slow" in the sense that we don't really know
> a precise time when we know that all devices have now shown up, there
> might always be slow devices that haven't popped up yet. Iterating
> through the entire tree of devices in sysfs is often quite slow in
> itself too, it's one of the most time consuming parts of the boot in
> fact. This all is done asynchronously hence: we
> enumerate/trigger/kmod all devices as quickly as we can, but we
> continue doing other stuff at the same time.
So let me make a suggestion that you can use now. Since all you
currently care about is the EFI/ACPI device, there is always a single
sysfs entry that corresponds to that (so you shouldn't need the log
entry as an indicator):
/sys/bus/acpi/devices/MSFT0101\:00
That link (or a kobject uevent if you prefer to look for that) will
always appear regardless of whether a driver has attached or not. When
the driver actually attaches, a driver/ directory will appear where the
link points.
The device link is added when the acpi scan is initiated as a
subsys_initcall, which is before all the filesystem initcalls, so it
should run before the initrd is mounted.
Is this enough for now and we can think about a more generic indicator
that all drivers have been probed later?
James
next prev parent reply other threads:[~2024-04-25 13:24 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240422112711.362779-1-mikko.rapeli@linaro.org>
[not found] ` <6e751959b9056884c1b9d3ba23e303d1737d8763.camel@HansenPartnership.com>
[not found] ` <ZiZhSfgeAdrbnaVL@nuoska>
[not found] ` <CAC_iWjKA-xRH=3FK+=woXsB8AW4+_mVhJhUQnL8iFKxGzOwKiA@mail.gmail.com>
2024-04-22 13:38 ` [PATCH] efi: expose TPM event log to userspace via sysfs James Bottomley
2024-04-22 13:54 ` Ilias Apalodimas
2024-04-22 14:31 ` James Bottomley
2024-04-22 15:22 ` Ilias Apalodimas
2024-04-24 17:15 ` Ard Biesheuvel
2024-04-25 8:56 ` Mikko Rapeli
2024-04-25 13:50 ` Jarkko Sakkinen
2024-04-25 9:58 ` Lennart Poettering
2024-04-25 10:36 ` Ard Biesheuvel
2024-04-25 11:13 ` Lennart Poettering
2024-04-25 11:47 ` Ilias Apalodimas
2024-04-25 13:36 ` Lennart Poettering
2024-04-25 13:46 ` James Bottomley
2024-04-25 13:24 ` James Bottomley [this message]
2024-04-25 13:39 ` Mikko Rapeli
2024-04-25 13:40 ` Lennart Poettering
2024-04-25 14:01 ` Jarkko Sakkinen
2024-04-26 7:35 ` Jarkko Sakkinen
2024-04-26 7:40 ` Jarkko Sakkinen
2024-04-26 8:19 ` Mikko Rapeli
2024-04-26 8:23 ` Jarkko Sakkinen
2024-04-22 14:57 ` Mikko Rapeli
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