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

Ian Campbell
2011-02-18T14:11:23Z

On Fri, 2011-02-18 at 14:07 +0000, Konrad Rzeszutek Wilk wrote:
> On Thu, Feb 17, 2011 at 09:30:03AM -0500, Konrad Rzeszutek Wilk wrote:
> > On Thu, Feb 17, 2011 at 08:41:31AM +0000, Ian Campbell wrote:
> > > 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.
> >
> > Which is OK. These are MSIs.
> > >
> > > 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
> >
> > Right.
> >
> > > only?) but a comment explaining this would be appreciated.
> >
> > Correct: "domU side".
> >
> > Will fix it up.
>
> How does this look to you?
>
> From eb832bece3131ecbdb509f7f2a9bc53f6692177c Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Date: Wed, 16 Feb 2011 13:43:04 -0500
> Subject: [PATCH 3/5] pci/xen: Use xen_allocate_pirq_msi instead of xen_allocate_pirq
>
> 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.
>
> All of this is uneccessary as this code path is only executed
> when we run as a domU PV guest with an MSI/MSI-X PCI card passed in.
> Hence we can jump straight to allocating an dynamic IRQ (and
> binding it to the proper PIRQ) and skip the rest.
>
> In short: this change is a cosmetic one.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Looks good,

Reviewed-by: Ian Campbell <ian.campbell@citrix.com>

BTW I'm currently testing a series of further cleanups, to the
xen_create_msi_irq and xen_allocate_pcirq_msi stuff in particular.

I hope to post it today, assuming my test boxes co-operate...

Ian.

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