[Xen-devel] [PATCH 1/3] x86-64/MMCFG: correct base address computation for regions not starting at bus 0

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

As per the specification, the base address reported by ACPI is the one
that would be used if the region started at bus 0. Hence the
start_bus_number offset needs to be added not only to the virtual
address, but also the physical one when establishing the mapping, and
it then needs to be subtracted when obtaining the virtual address for
doing accesses.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- a/xen/arch/x86/x86_64/mmconfig_64.c
+++ b/xen/arch/x86/x86_64/mmconfig_64.c
@@ -25,7 +25,7 @@ struct mmcfg_virt {
 static struct mmcfg_virt *pci_mmcfg_virt;
 static int __initdata mmcfg_pci_segment_shift;
 
-static char __iomem *get_virt(unsigned int seg, unsigned bus)
+static char __iomem *get_virt(unsigned int seg, unsigned int *bus)
 {
     struct acpi_mcfg_allocation *cfg;
     int cfg_num;
@@ -33,9 +33,11 @@ static char __iomem *get_virt(unsigned i
     for (cfg_num = 0; cfg_num < pci_mmcfg_config_num; cfg_num++) {
         cfg = pci_mmcfg_virt[cfg_num].cfg;
         if (cfg->pci_segment == seg &&
-            (cfg->start_bus_number <= bus) &&
-            (cfg->end_bus_number >= bus))
+            (cfg->start_bus_number <= *bus) &&
+            (cfg->end_bus_number >= *bus)) {
+            *bus -= cfg->start_bus_number;
             return pci_mmcfg_virt[cfg_num].virt;
+        }
     }
 
     /* Fall back to type 0 */
@@ -46,7 +48,7 @@ static char __iomem *pci_dev_base(unsign
 {
     char __iomem *addr;
 
-    addr = get_virt(seg, bus);
+    addr = get_virt(seg, &bus);
     if (!addr)
         return NULL;
      return addr + ((bus << 20) | (devfn << 12));
@@ -121,8 +123,11 @@ static void __iomem * __init mcfg_iorema
     if (virt + size < virt || virt + size > PCI_MCFG_VIRT_END)
         return NULL;
 
-    map_pages_to_xen(virt, cfg->address >> PAGE_SHIFT,
-                     size >> PAGE_SHIFT, PAGE_HYPERVISOR_NOCACHE);
+    if (map_pages_to_xen(virt,
+                         (cfg->address >> PAGE_SHIFT) +
+                         (cfg->start_bus_number << (20 - PAGE_SHIFT)),
+                         size >> PAGE_SHIFT, PAGE_HYPERVISOR_NOCACHE))
+        return NULL;
 
     return (void __iomem *) virt;
 }

Attachment: x86_64-mmcfg-base.patch
Description: Text document

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