Re: [Xen-devel] [PATCH 1/3] pci/xen: Use xen_allocate_pirq_msi

Ian Campbell
2011-02-17T08:41:36Z

On Wed, 2011-02-16 at 22:17 +0000, Konrad Rzeszutek Wilk wrote:
> There is no need to use the old interface.

xen_allocate_pirq -> xen_map_pirq_gsi -> PHYSDEVOP_alloc_irq_vector IFF
xen_initial_domain() in addition to the kernel side book-keeping side of
things (set chip and handler, update irq_info etc) whereas
xen_allocate_pirq_msi just does the kernel book keeping.

Also xen_allocate_pirq allocates an IRQ in the 1-1 GSI space whereas
xen_allocate_pirq_msi allocates a dynamic one in the >GSI IRQ space.

So this change is actually a semantic change and not just a switch to a
new interface. I think the change is OK (because the caller is domU
only?) but a comment explaining this would be appreciated.

> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> arch/x86/pci/xen.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
> index 25cd4a0..6432f75 100644
> --- a/arch/x86/pci/xen.c
> +++ b/arch/x86/pci/xen.c
> @@ -157,14 +157,14 @@ static int xen_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> goto error;
> i = 0;
> list_for_each_entry(msidesc, &dev->msi_list, list) {
> - irq = xen_allocate_pirq(v[i], 0, /* not sharable */
> + xen_allocate_pirq_msi(
> (type == PCI_CAP_ID_MSIX) ?
> - "pcifront-msi-x" : "pcifront-msi");
> + "pcifront-msi-x" : "pcifront-msi",
> + &irq, &v[i], XEN_ALLOC_IRQ);

All callers have this (type == MSIX) ? "msi-x" : "msi" construct,
differing only in their use of a "pcifront-" prefix. Something which
could be hoisted into the function perhaps?

Another aside: I think there are other cleanups which could be made to
the various pirq allocation/mapping interfaces (of which there seem to
be too many, or at least their individual unique qualities are
indistinguishable by their names), I made a start on this at one point
since I wanted to get rid of the pirq_to_irq[nr_irqs] array, for obvious
reasons, but didn't finish it off. I'll hopefully revisit this soon.

Ian.

> if (irq < 0) {
> ret = -1;
> goto free;
> }
> -
> ret = set_irq_msi(irq, msidesc);
> if (ret)
> goto error_while;