Messages in this thread | | | Subject | Re: [PATCH] iommu/amd: Fix event counter availability check | From | Paul Menzel <> | Date | Sun, 21 Feb 2021 14:44:36 +0100 |
| |
Dear Alexander,
Am 01.06.20 um 04:48 schrieb Paul Menzel:
[…]
> Am 31.05.20 um 09:22 schrieb Alexander Monakov: > >> Adding Shuah Khan to Cc: I've noticed you've seen this issue on Ryzen 2400GE; >> can you have a look at the patch? Would be nice to know if it fixes the >> problem for you too. > >> On Fri, 29 May 2020, Alexander Monakov wrote: >> >>> 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. > > I guess it’s a firmware bug, but I contacted the linux-pci folks [1].
Unfortunately, it’s still present in Linux 5.11.
>>> 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 > > Thank you very much for fixing this issue, which is almost two years old > for me. > > Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> > MSI MSI MS-7A37/B350M MORTAR with AMD Ryzen 3 2200G > Link: https://lore.kernel.org/linux-iommu/20180727102710.GA6738@8bytes.org/
Just a small note, that I am applying your patch, but it looks like there is still some timing issue. At least today, I noticed it during one boot with Linux 5.11. (Before I never noticed it again in the several years, but I am not always paying attention and do not save the logs.)
Kind regards,
Paul
> [1]: https://lore.kernel.org/linux-pci/8579bd14-e369-1141-917b-204d20cff528@molgen.mpg.de/
| |