linux-kernel - Re: [PATCH v2] xen: add support for MSI message groups

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Date:	Fri, 28 Feb 2014 13:00:22 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Roger Pau Monné <roger.pau@...rix.com>
CC:	xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH v2] xen: add support for MSI message groups

On 02/28/2014 12:46 PM, Roger Pau Monné wrote:
> On 28/02/14 18:20, Boris Ostrovsky wrote:
>> On 02/27/2014 01:45 PM, Boris Ostrovsky wrote:
>>> On 02/27/2014 01:15 PM, Roger Pau Monne wrote:
>>>> Add support for MSI message groups for Xen Dom0 using the
>>>> MAP_PIRQ_TYPE_MULTI_MSI pirq map type.
>>>>
>>>> In order to keep track of which pirq is the first one in the group all
>>>> pirqs in the MSI group except for the first one have the newly
>>>> introduced PIRQ_MSI_GROUP flag set. This prevents calling
>>>> PHYSDEVOP_unmap_pirq on them, since the unmap must be done with the
>>>> first pirq in the group.
>>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>>>
>>>
>>
>> I was just looking at xen_setup_msi_irqs() (for a different reason) and
>> I am no longer sure this patch does anything:
>>
>> static int xen_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
>> {
>>          int irq, ret, i;
>>          struct msi_desc *msidesc;
>>          int *v;
>>
>>          if (type == PCI_CAP_ID_MSI && nvec > 1)
>>                  return 1;
>> ....
>>
>> Same thing for xen_hvm_setup_msi_irqs().
> As said in the commit message this is only for Dom0, so the function
> modified is xen_initdom_setup_msi_irqs (were this check is removed).

Then what is the reason for these changes:

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 103e702..905956f 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -178,6 +178,7 @@ static int xen_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
  	i = 0;
  	list_for_each_entry(msidesc, &dev->msi_list, list) {
  		irq = xen_bind_pirq_msi_to_irq(dev, msidesc, v[i],
+					       (type == PCI_CAP_ID_MSI) ? nvec : 1,
  					       (type == PCI_CAP_ID_MSIX) ?
  					       "pcifront-msi-x" :
  					       "pcifront-msi",
@@ -245,6 +246,7 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
  				"xen: msi already bound to pirq=%d\n", pirq);
  		}
  		irq = xen_bind_pirq_msi_to_irq(dev, msidesc, pirq,
+					       (type == PCI_CAP_ID_MSI) ? nvec : 1,
  					       (type == PCI_CAP_ID_MSIX) ?
  					       "msi-x" : "msi",
  					       DOMID_SELF);

Should you simply pass 1?

-boris

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