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

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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>
This commit is contained in:
Tom Lendacky 2023-01-17 04:40:38 +00:00 committed by Joerg Roedel
parent 080920e521
commit 05d227efbd
1 changed files with 14 additions and 4 deletions
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18
drivers/iommu/amd/iommu.c
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@ -667,7 +667,14 @@ static void iommu_print_event(struct amd_iommu *iommu, void *__evt)
event[0], event[1], event[2], event[3]);
}
memset(__evt, 0, 4 * sizeof(u32));
/*
* 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));
}
static void iommu_poll_events(struct amd_iommu *iommu)
@ -736,10 +743,13 @@ 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.
*/
raw[0] = raw[1] = 0UL;
if (!amd_iommu_snp_en)
raw[0] = raw[1] = 0UL;
/* Update head pointer of hardware ring-buffer */
head = (head + PPR_ENTRY_SIZE) % PPR_LOG_SIZE;