From: Alex Williamson Date: Fri, 16 Sep 2022 20:44:48 +0000 (-0600) Subject: PCI: Expose PCIe Resizable BAR support via sysfs X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=91fa127794ac1c48069479b9d45eb4c7378c0e30;p=linux.git PCI: Expose PCIe Resizable BAR support via sysfs Add a simple sysfs interface to Resizable BAR support, largely for the purposes of assigning such devices to a VM through VFIO. Resizable BARs present a difficult feature to expose to a VM through emulation, as resizing a BAR is done on the host. It can fail, and often does, but we have no means via emulation of a PCIe REBAR capability to handle the error cases. A vfio-pci specific ioctl interface is also cumbersome as there are often multiple devices within the same bridge aperture and handling them is a challenge. In the interface proposed here, expanding a BAR potentially requires such devices to be soft-removed during the resize operation and rescanned after, in order for all the necessary resources to be released. A pci-sysfs interface is also more universal than a vfio specific interface. Please see the ABI documentation update for usage. Link: https://lore.kernel.org/r/166336088796.3597940.14973499936692558556.stgit@omen Signed-off-by: Alex Williamson Signed-off-by: Bjorn Helgaas Reviewed-by: Christian König Cc: Krzysztof Wilczyński --- diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 6fc2c2efe8ab2..840727fc75dcf 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -457,3 +457,36 @@ Description: The file is writable if the PF is bound to a driver that implements ->sriov_set_msix_vec_count(). + +What: /sys/bus/pci/devices/.../resourceN_resize +Date: September 2022 +Contact: Alex Williamson +Description: + These files provide an interface to PCIe Resizable BAR support. + A file is created for each BAR resource (N) supported by the + PCIe Resizable BAR extended capability of the device. Reading + each file exposes the bitmap of available resource sizes: + + # cat resource1_resize + 00000000000001c0 + + The bitmap represents supported resource sizes for the BAR, + where bit0 = 1MB, bit1 = 2MB, bit2 = 4MB, etc. In the above + example the device supports 64MB, 128MB, and 256MB BAR sizes. + + When writing the file, the user provides the bit position of + the desired resource size, for example: + + # echo 7 > resource1_resize + + This indicates to set the size value corresponding to bit 7, + 128MB. The resulting size is 2 ^ (bit# + 20). This definition + matches the PCIe specification of this capability. + + In order to make use of resource resizing, all PCI drivers must + be unbound from the device and peer devices under the same + parent bridge may need to be soft removed. In the case of + VGA devices, writing a resize value will remove low level + console drivers from the device. Raw users of pci-sysfs + resourceN attributes must be terminated prior to resizing. + Success of the resizing operation is not guaranteed. diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index fc804e08e3cb5..0a2eeb82cebde 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -28,6 +28,7 @@ #include #include #include +#include #include "pci.h" static int sysfs_initialized; /* = 0 */ @@ -1373,6 +1374,112 @@ static const struct attribute_group pci_dev_reset_attr_group = { .is_visible = pci_dev_reset_attr_is_visible, }; +#define pci_dev_resource_resize_attr(n) \ +static ssize_t resource##n##_resize_show(struct device *dev, \ + struct device_attribute *attr, \ + char * buf) \ +{ \ + struct pci_dev *pdev = to_pci_dev(dev); \ + ssize_t ret; \ + \ + pci_config_pm_runtime_get(pdev); \ + \ + ret = sysfs_emit(buf, "%016llx\n", \ + (u64)pci_rebar_get_possible_sizes(pdev, n)); \ + \ + pci_config_pm_runtime_put(pdev); \ + \ + return ret; \ +} \ + \ +static ssize_t resource##n##_resize_store(struct device *dev, \ + struct device_attribute *attr,\ + const char *buf, size_t count)\ +{ \ + struct pci_dev *pdev = to_pci_dev(dev); \ + unsigned long size, flags; \ + int ret, i; \ + u16 cmd; \ + \ + if (kstrtoul(buf, 0, &size) < 0) \ + return -EINVAL; \ + \ + device_lock(dev); \ + if (dev->driver) { \ + ret = -EBUSY; \ + goto unlock; \ + } \ + \ + pci_config_pm_runtime_get(pdev); \ + \ + if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA) { \ + ret = aperture_remove_conflicting_pci_devices(pdev, \ + "resourceN_resize"); \ + if (ret) \ + goto pm_put; \ + } \ + \ + pci_read_config_word(pdev, PCI_COMMAND, &cmd); \ + pci_write_config_word(pdev, PCI_COMMAND, \ + cmd & ~PCI_COMMAND_MEMORY); \ + \ + flags = pci_resource_flags(pdev, n); \ + \ + pci_remove_resource_files(pdev); \ + \ + for (i = 0; i < PCI_STD_NUM_BARS; i++) { \ + if (pci_resource_len(pdev, i) && \ + pci_resource_flags(pdev, i) == flags) \ + pci_release_resource(pdev, i); \ + } \ + \ + ret = pci_resize_resource(pdev, n, size); \ + \ + pci_assign_unassigned_bus_resources(pdev->bus); \ + \ + if (pci_create_resource_files(pdev)) \ + pci_warn(pdev, "Failed to recreate resource files after BAR resizing\n");\ + \ + pci_write_config_word(pdev, PCI_COMMAND, cmd); \ +pm_put: \ + pci_config_pm_runtime_put(pdev); \ +unlock: \ + device_unlock(dev); \ + \ + return ret ? ret : count; \ +} \ +static DEVICE_ATTR_RW(resource##n##_resize) + +pci_dev_resource_resize_attr(0); +pci_dev_resource_resize_attr(1); +pci_dev_resource_resize_attr(2); +pci_dev_resource_resize_attr(3); +pci_dev_resource_resize_attr(4); +pci_dev_resource_resize_attr(5); + +static struct attribute *resource_resize_attrs[] = { + &dev_attr_resource0_resize.attr, + &dev_attr_resource1_resize.attr, + &dev_attr_resource2_resize.attr, + &dev_attr_resource3_resize.attr, + &dev_attr_resource4_resize.attr, + &dev_attr_resource5_resize.attr, + NULL, +}; + +static umode_t resource_resize_is_visible(struct kobject *kobj, + struct attribute *a, int n) +{ + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj)); + + return pci_rebar_get_current_size(pdev, n) < 0 ? 0 : a->mode; +} + +static const struct attribute_group pci_dev_resource_resize_group = { + .attrs = resource_resize_attrs, + .is_visible = resource_resize_is_visible, +}; + int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev) { if (!sysfs_initialized) @@ -1494,6 +1601,7 @@ const struct attribute_group *pci_dev_groups[] = { #ifdef CONFIG_ACPI &pci_dev_acpi_attr_group, #endif + &pci_dev_resource_resize_group, NULL, };