From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Michael Kelley <mhklinux@outlook.com>
Cc: "haiyangz@microsoft.com" <haiyangz@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
"decui@microsoft.com" <decui@microsoft.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"hpa@zytor.com" <hpa@zytor.com>, "arnd@arndb.de" <arnd@arndb.de>,
"tytso@mit.edu" <tytso@mit.edu>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] x86/hyperv: Use Hyper-V entropy to seed guest random number generator
Date: Wed, 13 Mar 2024 22:33:05 -0600 [thread overview]
Message-ID: <CAHmME9rGm++fA+1=_MkPfdPEsKmDk_P8j_XnUoGC4rED7OYcgw@mail.gmail.com> (raw)
In-Reply-To: <BN7PR02MB4148FA0075DCB43F1971485BD4292@BN7PR02MB4148.namprd02.prod.outlook.com>
Hi Michael,
On Wed, Mar 13, 2024 at 10:30 PM Michael Kelley <mhklinux@outlook.com> wrote:
> By default, Linux doesn't verify checksums when accessing ACPI tables
> during early boot, though you can add "acpi_force_table_verification"
> to the kernel boot line. The default is shown in dmesg like this:
>
> [ 0.004419] ACPI: Early table checksum verification disabled
>
> The checksum of all tables is checked slightly later in boot, though
> it's after my entropy code has run. Without the checksum fixup,
> this error is output:
>
> [ 0.053752] ACPI BIOS Warning (bug): Incorrect checksum in table
> [OEM0] - 0x8B, should be 0x82 (20230628/utcksum-58)
>
> At this point, the checksum error doesn't really matter, but I
> don't want the warning showing up. I need to experiment a
> bit, but probably the best approach is to set the data length to
> zero (and adjust the checksum) while leaving the rest of the ACPI
> table header intact. It will be more difficult to make the table
> disappear entirely as it appears in a global list of ACPI tables.
That makes sense. If the length is getting set to zero and the data
itself zeroed, I would assume that the checksum evaluates to some
constant value (0? ~0? dunno how it's computed), so that should ease
things a bit.
Jason
prev parent reply other threads:[~2024-03-14 4:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-07 18:48 [PATCH v2 1/1] x86/hyperv: Use Hyper-V entropy to seed guest random number generator mhkelley58
2024-03-13 4:50 ` Long Li
2024-03-13 5:29 ` Michael Kelley
2024-03-13 16:36 ` Long Li
2024-03-13 23:32 ` Jason A. Donenfeld
2024-03-14 0:30 ` Michael Kelley
2024-03-14 3:05 ` Jason A. Donenfeld
2024-03-14 4:30 ` Michael Kelley
2024-03-14 4:33 ` Jason A. Donenfeld [this message]
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