[PATCH 2/3] tools/libxl: Grant permission for mapping opregions to the target domain

[Grzegorz Uriasz <gorbak25@xxxxxxxxx>]

IGD VGA devices require a special opregion MMIO region which functions as
an extra BAR in the PCI configuration space. Right now qemu is assigning those
permissions - this is failing inside a linux based stubdomain as the
stubdomain is not privileged. This patch grants the permissions for
opregions in libxl instead of qemu. Granting permissions in qemu may be removed
when this patch get's merged - for now linux based stubdomains which use IGD's
need to patch qemu and include this patch in xen for IGD passthrough to work.

Signed-off-by: Grzegorz Uriasz <gorbak25@xxxxxxxxx>
---
 tools/libxl/libxl_pci.c | 46 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
index 436190f790..48b1d8073b 100644
--- a/tools/libxl/libxl_pci.c
+++ b/tools/libxl/libxl_pci.c
@@ -2497,7 +2497,51 @@ static int libxl__grant_legacy_vga_permissions(libxl__gc 
*gc, const uint32_t dom
 }
 
 static int libxl__grant_igd_opregion_permission(libxl__gc *gc, const uint32_t 
domid) {
-    return 0;
+    char* sysfs_path;
+    FILE* f;
+    uint32_t igd_host_opregion;
+    int ret = 0;
+    uint32_t stubdom_domid = libxl_get_stubdom_id(CTX, domid);
+
+    sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/config", 0, 0, 2, 0);
+    f = fopen(sysfs_path, "r");
+    if (!f) {
+        LOGED(ERROR, domid, "Unable to access IGD config space");
+        return ERROR_FAIL;
+    }
+
+    ret = fseek(f, 0xfc, SEEK_SET);
+    if (ret < 0) {
+        LOGED(ERROR, domid, "Unable to lseek in PCI config space");
+        goto out;
+    }
+
+    ret = fread((void*)&igd_host_opregion, 4, 1, f);
+    if (ret < 0) {
+        LOGED(ERROR, domid, "Unable to read opregion register");
+        goto out;
+    }
+
+    ret = xc_domain_iomem_permission(CTX->xch, stubdom_domid,
+                                     (unsigned long)(igd_host_opregion >> 
XC_PAGE_SHIFT), 0x3, 1);
+    if (ret < 0) {
+        LOGED(ERROR, domid,
+              "failed to give stubdom%d access to %"PRIx32" opregions for igd 
passthrough", stubdom_domid, igd_host_opregion);
+        goto out;
+    }
+
+    ret = xc_domain_iomem_permission(CTX->xch, domid,
+                                     (unsigned long)(igd_host_opregion >> 
XC_PAGE_SHIFT), 0x3, 1);
+    if (ret < 0) {
+        LOGED(ERROR, domid,
+              "failed to give dom%d access to %"PRIx32" opregions for igd 
passthrough", domid, igd_host_opregion);
+        goto out;
+    }
+
+    out:
+    if(f)
+        fclose(f);
+    return ret;
 }
 
 int libxl__grant_vga_iomem_permission(libxl__gc *gc, const uint32_t domid,
-- 
2.27.0