Messages in this thread Patch in this message | | | From | Alexander Monakov <> | Subject | [PATCH] iommu/amd: Fix event counter availability check | Date | Fri, 29 May 2020 23:07:38 +0300 |
| |
The driver performs an extra check if the IOMMU's capabilities advertise presence of performance counters: it verifies that counters are writable by writing a hard-coded value to a counter and testing that reading that counter gives back the same value.
Unfortunately it does so quite early, even before pci_enable_device is called for the IOMMU, i.e. when accessing its MMIO space is not guaranteed to work. On Ryzen 4500U CPU, this actually breaks the test: the driver assumes the counters are not writable, and disables the functionality.
Moving init_iommu_perf_ctr just after iommu_flush_all_caches resolves the issue. This is the earliest point in amd_iommu_init_pci where the call succeeds on my laptop.
Signed-off-by: Alexander Monakov <amonakov@ispras.ru> Cc: Joerg Roedel <joro@8bytes.org> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> Cc: iommu@lists.linux-foundation.org ---
PS. I'm seeing another hiccup with IOMMU probing on my system: pci 0000:00:00.2: can't derive routing for PCI INT A pci 0000:00:00.2: PCI INT A: not connected
Hopefully I can figure it out, but I'd appreciate hints.
drivers/iommu/amd_iommu_init.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index 5b81fd16f5fa..1b7ec6b6a282 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -1788,8 +1788,6 @@ static int __init iommu_init_pci(struct amd_iommu *iommu) if (iommu->cap & (1UL << IOMMU_CAP_NPCACHE)) amd_iommu_np_cache = true; - init_iommu_perf_ctr(iommu); - if (is_rd890_iommu(iommu->dev)) { int i, j; @@ -1891,8 +1889,10 @@ static int __init amd_iommu_init_pci(void) init_device_table_dma(); - for_each_iommu(iommu) + for_each_iommu(iommu) { iommu_flush_all_caches(iommu); + init_iommu_perf_ctr(iommu); + } if (!ret) print_iommu_info(); base-commit: 75caf310d16cc5e2f851c048cd597f5437013368 -- 2.26.2
| |