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Re: [Xen-devel] [PATCH 09/28] ARM: GICv3 ITS: map device and LPIs to the ITS on physdev_op hypercall



Hi Julien,


On 01/31/2017 10:18 AM, Julien Grall wrote:


On 31/01/17 16:02, Jaggi, Manish wrote:


On 1/31/2017 8:47 PM, Julien Grall wrote:


On 31/01/17 14:08, Jaggi, Manish wrote:
Hi Julien,

On 1/31/2017 7:16 PM, Julien Grall wrote:
On 31/01/17 13:19, Jaggi, Manish wrote:
On 1/31/2017 6:13 PM, Julien Grall wrote:
On 31/01/17 10:29, Jaggi, Manish wrote:
If you please go back to your comment where you wrote "we need to find another way to get the DeviceID", I was referring that we should add that another way in this series so that correct DeviceID is programmed in ITS.

This is not the first time I am saying this, just saying "we should add that another way..." is not helpful. You should also provide some details on what you would do.

Julien, As you suggested we need to find another way, I assumed you had something in mind.

I gave suggestions on my e-mail but you may have missed it...

Since we both agree that sbdf!=deviceID, the current series of ITS patches will program the incorrect deviceID so there is a need to
have a way to map sbdf with deviceID in xen.

One option could be to add a new hypercall to supply sbdf and deviceID to xen.

... as well as the part where I am saying that I am not in favor to
implement an hypercall temporarily, and against adding a new hypercall
for only a couple of weeks. As you may know PHYSDEV hypercall are part
of the stable ABI and once they are added they cannot be removed.

So we need to be sure the hypercall is necessary. In this case, the
hypercall is not necessary as all the information can be found in the
firmware tables. However this is not implemented yet and part of the
discussion on PCI Passthrough (see [1]).

We need a temporary solution that does not involve any commitment on the
ABI until Xen is able to discover PCI.


Why can't we handle ITS device creation whenever a virtual ITS driver receives the MAPD command from dom0/domU. In case of dom0, it's straight forward dom0 always passes the real ITS device through MAPD command. This way we can support PCIe devices without hard-coded MSI(x) limit 32, and platform devices transparently. I used the below code to platform and PCIe device MSI(x) functionality on QDF2400 server platform.

@@ -383,10 +384,17 @@ static int its_handle_mapd(struct virt_its *its, uint64_t *cmdptr)
     int size = its_cmd_get_size(cmdptr);
     bool valid = its_cmd_get_validbit(cmdptr);
paddr_t itt_addr = its_cmd_mask_field(cmdptr, 2, 0, 52) & GENMASK(51, 8);
+    int ret;

     if ( !its->dev_table )
         return -1;

+    size = size < 4 ? 4 : size;
+ ret = gicv3_its_map_guest_device(hardware_domain, devid, devid, size + 1,
+                                     valid);
+    if (ret < 0)
+        return ret;
+


--
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux 
Foundation Collaborative Project.


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