Commit 05d227ef authored Jan 17, 2023 by Tom Lendacky Committed by Joerg Roedel Jan 20, 2023

iommu/amd: Do not clear event/ppr log buffer when snp is enabled

Current code clears event log and ppr log entry after processing it due
to hardware errata ([1]  erratum #732, #733). We do not have hardware
issue on SNP enabled system.

When SNP is enabled, the event logs, PPR log and completion wait buffer
are read-only to the host (see SNP FW ABI spec [2]). Clearing those entry
will result in a kernel #PF for an RMP violation. Hence do not clear
event and ppr log entry after processing it.

[1] http://developer.amd.com/wordpress/media/2012/10/48931_15h_Mod_10h-1Fh_Rev_Guide.pdf
[2] https://www.amd.com/system/files/TechDocs/56860.pdf



Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20230117044038.5728-1-vasant.hegde@amd.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>

parent 080920e5

drivers/iommu/amd/iommu.c

+14 −4

Original line number	Diff line number	Diff line
		@@ -667,6 +667,13 @@ static void iommu_print_event(struct amd_iommu iommu, void __evt)
		event[0], event[1], event[2], event[3]);
		}

		/*
		* To detect the hardware errata 732 we need to clear the
		* entry back to zero. This issue does not exist on SNP
		* enabled system. Also this buffer is not writeable on
		* SNP enabled system.
		*/
		if (!amd_iommu_snp_en)
		memset(__evt, 0, 4 * sizeof(u32));
		}

		@@ -736,9 +743,12 @@ static void iommu_poll_ppr_log(struct amd_iommu *iommu)
		entry[1] = raw[1];

		/*
		* To detect the hardware bug we need to clear the entry
		* back to zero.
		* To detect the hardware errata 733 we need to clear the
		* entry back to zero. This issue does not exist on SNP
		* enabled system. Also this buffer is not writeable on
		* SNP enabled system.
		*/
		if (!amd_iommu_snp_en)
		raw[0] = raw[1] = 0UL;

		/* Update head pointer of hardware ring-buffer */