PCI Express Capability RMW accessors don't properly protect against concurrent access. Link Control Register is written by a number of things in the kernel in a RMW fashion without any concurrency control. This could in the unlucky case lead to losing one of the updates. One of the most obvious path which can race with most of the other LNKCTL RMW operations seems to be ASPM policy sysfs write which triggers LNKCTL update. Similarly, Root Control Register can be concurrently accessed by AER and PME. Make pcie_capability_clear_and_set_word() (and other RMW accessors that call it) to use a per device spinlock to protect the RMW operations to the Capability Registers that require locking. Convert open-coded LNKCTL RMW operations to use pcie_capability_clear_and_set_word() to benefit from the locking. As for LNKCTL2, all current users are safe so I left those changes to be part of PCIe bandwidth control work I'll send separately later. It will add LNKCTL2 RMW ops that require locking. I went with the wrapper approach I suggested to Lukas even if I personally feel it's over-engineering for a case that doesn't current exist in the kernel code. That, however, is contained in the first patch so it can be easily changed without affecting the other patches. I felt better to do these as fixes first before altering code related to duplicated ASPM code in drivers. Replacing the custom ASPM code in drivers with calls to core will not necessarily yield the same states as previously even if disabling ASPM becomes always possible because re-enabling ASPM would still be prohibited (some drivers do disable and enable ASPM back later). Thus, the ASPM "cleanups" would have higher regression potential. The series is based on top of the "PCI/ASPM: Handle link retraining race" patch I sent earlier but is not yet applied. v2: - Keep the RMW ops caller API the same - Make pcie_capability_clear_and_set_word() a wrapper that uses locked/unlocked variant based on the capability reg - Extracted LNKCTL2 changes out from this series to keep this purely a series which fixes something (LNKCTL2 RMW lock is necessary only when PCIe BW control is introduced). - Added Fixes tags (it's a bit rathole but yeah, they're there now). - Renamed cap_lock to pcie_cap_lock - Changed ath1* to clear the ASPMC field before setting it Ilpo Järvinen (9): PCI: Add locking to RMW PCI Express Capability Register accessors PCI: pciehp: Use RMW accessors for changing LNKCTL PCI/ASPM: Use RMW accessors for changing LNKCTL drm/amdgpu: Use RMW accessors for changing LNKCTL drm/radeon: Use RMW accessors for changing LNKCTL net/mlx5: Use RMW accessors for changing LNKCTL wifi: ath11k: Use RMW accessors for changing LNKCTL wifi: ath12k: Use RMW accessors for changing LNKCTL wifi: ath10k: Use RMW accessors for changing LNKCTL drivers/gpu/drm/amd/amdgpu/cik.c | 36 +++++------------ drivers/gpu/drm/amd/amdgpu/si.c | 36 +++++------------ drivers/gpu/drm/radeon/cik.c | 36 +++++------------ drivers/gpu/drm/radeon/si.c | 37 +++++------------- .../ethernet/mellanox/mlx5/core/fw_reset.c | 9 +---- drivers/net/wireless/ath/ath10k/pci.c | 9 +++-- drivers/net/wireless/ath/ath11k/pci.c | 10 +++-- drivers/net/wireless/ath/ath12k/pci.c | 10 +++-- drivers/pci/access.c | 20 ++++++++-- drivers/pci/hotplug/pciehp_hpc.c | 12 ++---- drivers/pci/pcie/aspm.c | 39 ++++++++----------- drivers/pci/probe.c | 1 + include/linux/pci.h | 34 +++++++++++++++- 13 files changed, 128 insertions(+), 161 deletions(-) -- 2.30.2
