[PATCH] xen/pt: Emulate multifunction bit in header type

[PATCH] xen/pt: Emulate multifunction bit in header type

[Ross Lagerwall via]

The intention of the code appears to have been to unconditionally set
the multifunction bit but since the emulation mask is 0x00 it has no
effect. Instead, emulate the bit and set it based on the multifunction
property of the PCIDevice (which can be set using QAPI).

This allows making passthrough devices appear as functions in a Xen
guest.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
---
 hw/xen/xen_pt_config_init.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
index 2b8680b112fa..e6ec32e3ccd2 100644
--- a/hw/xen/xen_pt_config_init.c
+++ b/hw/xen/xen_pt_config_init.c
@@ -291,7 +291,10 @@ static int xen_pt_header_type_reg_init(XenPCIPassthroughState *s,
                                        uint32_t *data)
 {
     /* read PCI_HEADER_TYPE */
-    *data = reg->init_val | 0x80;
+    *data = reg->init_val;
+    if ((PCI_DEVICE(s)->cap_present & QEMU_PCI_CAP_MULTIFUNCTION)) {
+        *data |= PCI_HEADER_TYPE_MULTI_FUNCTION;
+    }
     return 0;
 }
 
@@ -676,7 +679,7 @@ static XenPTRegInfo xen_pt_emu_reg_header0[] = {
         .size       = 1,
         .init_val   = 0x00,
         .ro_mask    = 0xFF,
-        .emu_mask   = 0x00,
+        .emu_mask   = PCI_HEADER_TYPE_MULTI_FUNCTION,
         .init       = xen_pt_header_type_reg_init,
         .u.b.read   = xen_pt_byte_reg_read,
         .u.b.write  = xen_pt_byte_reg_write,
-- 
2.41.0

Re: [PATCH] xen/pt: Emulate multifunction bit in header type

[Paul Durrant]

On 03/11/2023 17:26, Ross Lagerwall wrote:
> The intention of the code appears to have been to unconditionally set
> the multifunction bit but since the emulation mask is 0x00 it has no
> effect. Instead, emulate the bit and set it based on the multifunction
> property of the PCIDevice (which can be set using QAPI).
> 
> This allows making passthrough devices appear as functions in a Xen
> guest.
> 
> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>

Reviewed-by: Paul Durrant <paul@xen.org>