From: "NOMURA JUNICHI(野村 淳一)" <junichi.nomura@nec.com>
To: Yian Chen <yian.chen@intel.com>
Cc: "iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"jroedel@suse.de" <jroedel@suse.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iommu/vt-d: Check VT-d RMRR region in BIOS is reported as reserved
Date: Tue, 18 Feb 2020 08:28:34 +0000 [thread overview]
Message-ID: <64a5843d-850d-e58c-4fc2-0a0eeeb656dc@nec.com> (raw)
In-Reply-To: <20191015164932.18185-1-yian.chen@intel.com>
Hi,
On 10/16/19 1:49 AM, Yian Chen wrote:
> VT-d RMRR (Reserved Memory Region Reporting) regions are reserved
> for device use only and should not be part of allocable memory pool of OS.
>
> BIOS e820_table reports complete memory map to OS, including OS usable
> memory ranges and BIOS reserved memory ranges etc.
>
> x86 BIOS may not be trusted to include RMRR regions as reserved type
> of memory in its e820 memory map, hence validate every RMRR entry
> with the e820 memory map to make sure the RMRR regions will not be
> used by OS for any other purposes.
I found "bad RMRR" warnings starting to appear on some x86 servers
since v5.5-rc1 and it gets even louder since v5.6-rc1. The "bad"
RMRR is for the area resides in ACPI NVS memory region. For example,
# dmesg|grep RMRR
DMAR: RMRR base: 0x000000a2290000 end: 0x000000a2292fff
DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR [0x00000000a2290000-0x00000000a2292fff], contact BIOS vendor for fixes
Your BIOS is broken; bad RMRR [0x00000000a2290000-0x00000000a2292fff]
# dmesg|grep NVS
BIOS-e820: [mem 0x00000000a067a000-0x00000000a2a79fff] ACPI NVS
reserve setup_data: [mem 0x00000000a067a000-0x00000000a2a79fff] ACPI NVS
PM: Registering ACPI NVS region [mem 0xa067a000-0xa2a79fff] (37748736 bytes)
The warnings come from arch_rmrr_sanity_check() since it checks whether
the region is E820_TYPE_RESERVED. However, if the purpose of the check
is to detect RMRR has regions that may be used by OS as free memory,
isn't E820_TYPE_NVS safe, too?
--
Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.
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prev parent reply other threads:[~2020-02-18 10:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 16:49 [PATCH] iommu/vt-d: Check VT-d RMRR region in BIOS is reported as reserved Yian Chen
2019-10-16 0:25 ` Lu Baolu
2019-10-16 7:51 ` Joerg Roedel
2019-10-16 17:21 ` Chen, Yian
2020-02-18 8:28 ` NOMURA JUNICHI(野村 淳一) [this message]
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