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iommu/amd: Fix IOMMU perf counter clobbering during init 

init_iommu_perf_ctr() clobbers the register when it checks write access
to IOMMU perf counters and fails to restore when they are writable.

Add save and restore to fix it.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Fixes: 30861ddc9c ("perf/x86/amd: Add IOMMU Performance Counter resource management")
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Shuah Khan 2020-01-23 15:32:14 -07:00 committed by Joerg Roedel
parent bf708cfb2f
commit 8c17bbf6c8
1 changed files with 18 additions and 6 deletions
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24
drivers/iommu/amd_iommu_init.c
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@ -1655,27 +1655,39 @@ static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
static void init_iommu_perf_ctr(struct amd_iommu *iommu)
{
struct pci_dev *pdev = iommu->dev;
u64 val = 0xabcd, val2 = 0;
u64 val = 0xabcd, val2 = 0, save_reg = 0;
if (!iommu_feature(iommu, FEATURE_PC))
return;
amd_iommu_pc_present = true;
/* save the value to restore, if writable */
if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
goto pc_false;
/* Check if the performance counters can be written to */
if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
(iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
(val != val2)) {
pci_err(pdev, "Unable to write to IOMMU perf counter.\n");
amd_iommu_pc_present = false;
return;
}
(val != val2))
goto pc_false;
/* restore */
if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
goto pc_false;
pci_info(pdev, "IOMMU performance counters supported\n");
val = readl(iommu->mmio_base + MMIO_CNTR_CONF_OFFSET);
iommu->max_banks = (u8) ((val >> 12) & 0x3f);
iommu->max_counters = (u8) ((val >> 7) & 0xf);
return;
pc_false:
pci_err(pdev, "Unable to read/write to IOMMU perf counter.\n");
amd_iommu_pc_present = false;
return;
}
static ssize_t amd_iommu_show_cap(struct device *dev,