On 25/05/16 16:55, Andre Przywara wrote:

Hi Christoffer,

On 03/04/16 10:15, Christoffer Dall wrote:

quoted

On Sat, Mar 26, 2016 at 02:13:59AM +0000, Andre Przywara wrote:

quoted

The ARM GICv3 ITS MSI controller requires a device ID to be able to
assign the proper interrupt vector. On real hardware, this ID is
sampled from the bus. To be able to emulate an ITS controller, extend
the KVM MSI interface to let userspace provide such a device ID. For
PCI devices, the device ID is simply the 16-bit bus-device-function
triplet, which should be easily available to the userland tool.

Also there is a new KVM capability which advertises whether the
current VM requires a device ID to be set along with the MSI data.
This flag is still reported as not available everywhere, later we will
enable it when ITS emulation is used.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Eric Auger <redacted>
---
 Documentation/virtual/kvm/api.txt | 12 ++++++++++--
 include/uapi/linux/kvm.h          |  5 ++++-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index cb2ef0b..8f7351d 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt

@@ -2163,10 +2163,18 @@ struct kvm_msi {
 	__u32 address_hi;
 	__u32 data;
 	__u32 flags;
-	__u8  pad[16];
+	__u32 devid;

Are we imposing any unfortunate restrictions for other architectures by
using a u32 over a u64 for the device ID?

Mmmh, good point. I guess not only for other architectures, but also for
the future in general.

Are there any objections against increasing this to a u64?

I'm not sure this is really necessary. A PCI RID is 16bit, and expanding
it to 32bit is already making quite a bit of space for further extension.

Also, some architecture might be unhappy of having a 64bit quantity that
is not 64bit aligned...

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...