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Describe generic PCI driver quiescing, exclusive HDM range reservation, cache and IOMMU handling, function-scope restrictions, and state restoration. Clarify that the method does not offline memory or revoke mappings, and that it requests CXL Reset Memory Clear. Signed-off-by: Srirangan Madhavan --- Documentation/ABI/testing/sysfs-bus-pci | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 55ea1db749a1..248d4f427589 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -153,6 +153,31 @@ Description: "default" enables all supported reset methods in the default ordering. + If present, "cxl_reset" selects CXL Reset for CXL Type 2 + devices that advertise CXL Reset and CXL Reset Memory Clear + support. The method is only listed for single-function devices, + and reset is rejected if the device has enabled VFs, so CXL Reset + cannot affect another PCI function. + + When reset is triggered through the reset attribute, the generic + PCI reset path calls the device driver's reset_prepare() callback, + when provided, and disables PCI I/O, memory decoding, and bus + mastering before invoking this method. + The method then rejects the operation if cached HDM state is + unavailable or an affected HDM range cannot be exclusively + reserved. It does not offline memory or revoke mappings; CXL.mem + users are expected to retain conflicting iomem resources while + access to an affected range remains active. + + Before issuing CXL Reset, the kernel invalidates CPU caches for + affected HDM ranges where supported, disables CXL.cache, initiates + cache write-back where supported, and blocks IOMMU translations + where applicable. After reset, it restores PCI config state needed + to access HDM MMIO, cached HDM decoder state, and the CXL Device + DVSEC Cache and Mem Enable controls before completing PCI reset + recovery. "cxl_reset" requests CXL Reset Memory Clear so that a + successful generic PCI reset does not preserve tenant memory. + What: /sys/bus/pci/devices/.../reset Date: July 2009 Contact: Michael S. Tsirkin -- 2.43.0