linux-kernel - Re: [Xen-devel] [PATCH 1/3] pci/xen: Use xen_allocate_pirq

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Date:	Fri, 18 Feb 2011 14:11:18 +0000
From:	Ian Campbell <Ian.Campbell@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Konrad Rzeszutek Wilk <konrad@...nel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [Xen-devel] [PATCH 1/3] pci/xen: Use xen_allocate_pirq_msi

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@...cle.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@...cle.com>

Looks good,

Reviewed-by: Ian Campbell <ian.campbell@...rix.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;


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