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Date: Wed, 2 Feb 2022 16:41:46 +0100
From: Borislav Petkov <bp@...en8.de>
To: Brijesh Singh <brijesh.singh@....com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
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Andy Lutomirski <luto@...nel.org>,
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brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v9 18/43] x86/kernel: Validate ROM memory before
accessing when SEV-SNP is active
On Fri, Jan 28, 2022 at 11:17:39AM -0600, Brijesh Singh wrote:
> @@ -197,11 +198,21 @@ static int __init romchecksum(const unsigned char *rom, unsigned long length)
>
> void __init probe_roms(void)
> {
> - const unsigned char *rom;
> unsigned long start, length, upper;
> + const unsigned char *rom;
> unsigned char c;
> int i;
>
> + /*
> + * The ROM memory is not part of the E820 system RAM and is not pre-validated
> + * by the BIOS. The kernel page table maps the ROM region as encrypted memory,
> + * the SEV-SNP requires the encrypted memory must be validated before the
> + * access. Validate the ROM before accessing it.
> + */
Lemme massage it:
/*
* The ROM memory range is not part of the e820 table and is therefore not
* pre-validated by BIOS. The kernel page table maps the ROM region as encrypted
* memory, and SEV-SNP requires encrypted memory to be validated before access.
* Do that here.
*/
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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