diff options
| author | Yongji Xie <elohimes@gmail.com> | 2017-04-10 19:58:12 +0800 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2017-04-19 12:51:25 -0500 |
| commit | 0a701aa6378496ea54fb065c68b41d918e372e94 (patch) | |
| tree | 333c248bd0b7d7abbd8b249cd63e0f5753f3c267 /drivers/pci | |
| parent | c9c75143a5962c4c26d2f2c99b7a6e06f421f5e1 (diff) | |
PCI: Add pcibios_default_alignment() for arch-specific alignment control
When VFIO passes through a PCI device to a guest, it does not allow the
guest to mmap BARs that are smaller than PAGE_SIZE unless it can reserve
the rest of the page (see vfio_pci_probe_mmaps()). This is because a page
might contain several small BARs for unrelated devices and a guest should
not be able to access all of them.
VFIO emulates guest accesses to non-mappable BARs, which is functional but
slow. On systems with large page sizes, e.g., PowerNV with 64K pages, BARs
are more likely to share a page and performance is more likely to be a
problem.
Add a weak function to set default alignment for all PCI devices. An arch
can override it to force the PCI core to place memory BARs on their own
pages.
Signed-off-by: Yongji Xie <elohimes@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci')
| -rw-r--r-- | drivers/pci/pci.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 679af2a253ad..d22fb35be26e 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4947,6 +4947,11 @@ void pci_ignore_hotplug(struct pci_dev *dev) } EXPORT_SYMBOL_GPL(pci_ignore_hotplug); +resource_size_t __weak pcibios_default_alignment(void) +{ + return 0; +} + #define RESOURCE_ALIGNMENT_PARAM_SIZE COMMAND_LINE_SIZE static char resource_alignment_param[RESOURCE_ALIGNMENT_PARAM_SIZE] = {0}; static DEFINE_SPINLOCK(resource_alignment_lock); @@ -4962,14 +4967,15 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev) { int seg, bus, slot, func, align_order, count; unsigned short vendor, device, subsystem_vendor, subsystem_device; - resource_size_t align = 0; + resource_size_t align = pcibios_default_alignment(); char *p; spin_lock(&resource_alignment_lock); p = resource_alignment_param; - if (!*p) + if (!*p && !align) goto out; if (pci_has_flag(PCI_PROBE_ONLY)) { + align = 0; pr_info_once("PCI: Ignoring requested alignments (PCI_PROBE_ONLY)\n"); goto out; } |