Re: [Xen-devel] [PATCH] Re-enable LTR/OBFF when device is owned by pciback

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Sun, Apr 22, 2012 at 03:25:04PM +0000, Hao, Xudong wrote:
> When PCIE device which has LTR/OBFF capabilities is owned by pciback, 
> LTR/OBFF feature may be disabled. This patch re-enable LTR and OBFF, so that 
> guest with device assigned can be benefitted.

Shouldn't they be reset when the device is de-assigned from the guest as well?
> 
> Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
> 
> diff --git a/drivers/xen/xen-pciback/pci_stub.c 
> b/drivers/xen/xen-pciback/pci_stub.c
> index 19834d1..82aac5b 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -334,6 +334,14 @@ static int __devinit pcistub_init_device(struct pci_dev 
> *dev)
>       dev_dbg(&dev->dev, "reset device\n");
>       xen_pcibk_reset_device(dev);
>  
> +     /* set default value */
> +     unsigned long type = PCI_EXP_OBFF_SIGNAL_ALWAYS;
> +     int snoop_lat_ns = 1024, nosnoop_lat_ns = 1024; /* 1024ns is max value 
> */


Please put them in the appropiate location - at the start of the 
function.

> +
> +     /* Enable LTR and OBFF before do device assignment */
> +     /* LTR(Latency tolerance reporting) allows devices to send messages to 
> the
> +      * root complex indicating their latency tolerance for snooped & 
> unsnooped
> +      * memory transactions. 
> +      */
> +     pci_enable_ltr(dev);
> +     pci_set_ltr(dev, snoop_lat_ns, nosnoop_lat_ns);

OK, but didn't you just come with up those values?

> +
> +     /* OBFF (optimized buffer flush/fill), where supported, can help improve
> +      * energy efficiency by giving devices information about when 
> interrupts and
> +      * other activity will have a reduced power impact.
> +      */
> +     pci_enable_obff(dev, type);
> +
>       dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
>       return 0;

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