From: Charlotte Tan charlotte@extrahop.com
[ Upstream commit 5566e68d829f5d87670d5984c1c2ccb4c518405f ]
arch_rmrr_sanity_check() warns if the RMRR is not covered by an ACPI Reserved region, but it seems like it should accept an NVS region as well. The ACPI spec https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html uses similar wording for "Reserved" and "NVS" region types; for NVS regions it says "This range of addresses is in use or reserved by the system and must not be used by the operating system."
There is an old comment on this mailing list that also suggests NVS regions should pass the arch_rmrr_sanity_check() test:
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?
This patch overlaps with another proposed patch that would add the region type to the log since sometimes the bug reporter sees this log on the console but doesn't know to include the kernel log:
https://lore.kernel.org/lkml/20220611204859.234975-3-atomlin@redhat.com/
Here's an example of the "Firmware Bug" apparent false positive (wrapped for line length):
DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR [0x000000006f760000-0x000000006f762fff], contact BIOS vendor for fixes DMAR: [Firmware Bug]: Your BIOS is broken; bad RMRR [0x000000006f760000-0x000000006f762fff]
This is the snippet from the e820 table:
BIOS-e820: [mem 0x0000000068bff000-0x000000006ebfefff] reserved BIOS-e820: [mem 0x000000006ebff000-0x000000006f9fefff] ACPI NVS BIOS-e820: [mem 0x000000006f9ff000-0x000000006fffefff] ACPI data
Fixes: f036c7fa0ab6 ("iommu/vt-d: Check VT-d RMRR region in BIOS is reported as reserved") Cc: Will Mortensen will@extrahop.com Link: https://lore.kernel.org/linux-iommu/64a5843d-850d-e58c-4fc2-0a0eeeb656dc@nec... Link: https://bugzilla.kernel.org/show_bug.cgi?id=216443 Signed-off-by: Charlotte Tan charlotte@extrahop.com Reviewed-by: Aaron Tomlin atomlin@redhat.com Link: https://lore.kernel.org/r/20220929044449.32515-1-charlotte@extrahop.com Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/iommu.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h index 0bef44d30a27..2fd52b65deac 100644 --- a/arch/x86/include/asm/iommu.h +++ b/arch/x86/include/asm/iommu.h @@ -25,8 +25,10 @@ arch_rmrr_sanity_check(struct acpi_dmar_reserved_memory *rmrr) { u64 start = rmrr->base_address; u64 end = rmrr->end_address + 1; + int entry_type;
- if (e820__mapped_all(start, end, E820_TYPE_RESERVED)) + entry_type = e820__get_entry_type(start, end); + if (entry_type == E820_TYPE_RESERVED || entry_type == E820_TYPE_NVS) return 0;
pr_err(FW_BUG "No firmware reserved region can cover this RMRR [%#018Lx-%#018Lx], contact BIOS vendor for fixes\n",