[PATCH v6 2/3] PCI: Allow ATS to be always on for pre-CXL devices
From: Nicolin Chen <hidden>
Date: 2026-05-21 20:34:54
Also in:
linux-cxl, linux-iommu, linux-pci, lkml
Subsystem:
pci subsystem, the rest · Maintainers:
Bjorn Helgaas, Linus Torvalds
Some NVIDIA GPU/NIC devices, though they don't implement CXL config space, have many CXL-like properties. Call this kind "pre-CXL". Similar to CXL.cache capability, these pre-CXL devices also require the ATS function even when their RIDs are IOMMU bypassed, i.e. keep ATS "always on" v.s. "on demand" when a non-zero PASID line gets enabled in SVA use cases. Introduce pci_dev_specific_ats_required() quirk function to scan a list of IDs for these devices. Then, include it in pci_ats_required(). Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Nirmoy Das <redacted> Tested-by: Nirmoy Das <redacted> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Dave Jiang <dave.jiang@intel.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Nicolin Chen <redacted> --- drivers/pci/pci.h | 9 +++++++++ drivers/pci/ats.c | 3 ++- drivers/pci/quirks.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 4a14f88e543a2..e8ad27abb1cfe 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h@@ -1155,6 +1155,15 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, bool probe) } #endif +#if defined(CONFIG_PCI_QUIRKS) && defined(CONFIG_PCI_ATS) +bool pci_dev_specific_ats_required(struct pci_dev *dev); +#else +static inline bool pci_dev_specific_ats_required(struct pci_dev *dev) +{ + return false; +} +#endif + #if defined(CONFIG_PCI_QUIRKS) && defined(CONFIG_ARM64) int acpi_get_rc_resources(struct device *dev, const char *hid, u16 segment, struct resource *res);
diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 84cd06d74fc9c..96efa00d97433 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c@@ -247,7 +247,8 @@ bool pci_ats_required(struct pci_dev *pdev) if (pdev->is_virtfn) pdev = pci_physfn(pdev); - return pci_cxl_ats_required(pdev); + return pci_cxl_ats_required(pdev) || + pci_dev_specific_ats_required(pdev); } EXPORT_SYMBOL_GPL(pci_ats_required);
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index caaed1a01dc02..c0242f3e9f063 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c@@ -5715,6 +5715,48 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1457, quirk_intel_e2000_no_ats); DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1459, quirk_intel_e2000_no_ats); DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x145a, quirk_intel_e2000_no_ats); DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x145c, quirk_intel_e2000_no_ats); + +static bool quirk_nvidia_gpu_ats_required(struct pci_dev *pdev) +{ + switch (pdev->device) { + case 0x2e00 ... 0x2e3f: /* GB20B */ + return true; + } + return false; +} + +static const struct pci_dev_ats_required { + u16 vendor; + u16 device; + bool (*ats_required)(struct pci_dev *dev); +} pci_dev_ats_required[] = { + /* NVIDIA GPUs */ + { PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID, quirk_nvidia_gpu_ats_required }, + /* NVIDIA CX10 Family NVlink-C2C */ + { PCI_VENDOR_ID_MELLANOX, 0x2101, NULL }, + { 0 } +}; + +/* + * Some NVIDIA devices do not implement CXL config space, but present as PCIe + * devices that can issue CXL-like cache operations like CXL.cache. Thus, they + * require ATS to obtain host physical addresses, like pci_cxl_ats_required(). + */ +bool pci_dev_specific_ats_required(struct pci_dev *pdev) +{ + const struct pci_dev_ats_required *i; + + for (i = pci_dev_ats_required; i->vendor; i++) { + if (i->vendor != pdev->vendor) + continue; + if (i->ats_required && i->ats_required(pdev)) + return true; + if (!i->ats_required && i->device == pdev->device) + return true; + } + + return false; +} #endif /* CONFIG_PCI_ATS */ /* Freescale PCIe doesn't support MSI in RC mode */
--
2.43.0