Re: [Xen-devel] [PATCH 2/3] xen-pcifront: Sanity check the MSI/MSI-X values

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2011-02-16 at 22:17 +0000, Konrad Rzeszutek Wilk wrote:
> Check the returned vector values for any values that are
> odd or plain incorrect (say vector value zero), and if so
> print a warning. Also fixup the return values.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  drivers/pci/xen-pcifront.c |   17 ++++++++++++++---
>  1 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index 3a5a6fc..6acf6ae 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -277,13 +277,20 @@ static int pci_frontend_enable_msix(struct pci_dev *dev,
>  	if (likely(!err)) {
>  		if (likely(!op.value)) {
>  			/* we get the result */
> -			for (i = 0; i < nvec; i++)
> +			for (i = 0; i < nvec; i++) {
> +				if (op.msix_entries[i].vector <= 0) {
> +					dev_warn(&dev->dev, "MSI-X entry %d" \
> +						" is zero!\n", i);

The test says "<= 0" but the text says "== 0". Perhaps
					dev_warn(&dev->dev, "MSI-X entry %d has invalid vector %d\n",
						 i, op.msix_entries[i].vector);

> 
> +					err = -EINVAL;
> +					continue;

Do we need / should we set *(*vector+i) to something to indicate its
invalidness rather than leave it potentially uninitialised?

> +				}
>  				*(*vector+i) = op.msix_entries[i].vector;

BTW does the double indirection of the vector serve a purpose?
Everywhere I can see just updates *(*vector+i), I can't see any realloc
of the array itself etc.

Removing the extra level of indirection leads to vector[i] = foo instead
which is much easier on the eye.

> -			return 0;
> +			}
> +			return err;
>  		} else {
>  			printk(KERN_DEBUG "enable msix get value %x\n",
>  				op.value);
> -			return op.value;
> +			return err;

I think all of these "return err"s can now be pulled out to the end of
the function? makes it clearer what the return is.

>  		}
>  	} else {
>  		dev_err(&dev->dev, "enable msix get err %x\n", err);
> @@ -325,6 +332,10 @@ static int pci_frontend_enable_msi(struct pci_dev *dev, int **vector)
>  	err = do_pci_op(pdev, &op);
>  	if (likely(!err)) {
>  		*(*vector) = op.value;
> +		if (op.value <= 0) {
> +			dev_warn(&dev->dev, "MSI entry is zero!\n");

Same comment re <= vs == 0.

> +			err = -EINVAL;
> +		}
>  	} else {
>  		dev_err(&dev->dev, "pci frontend enable msi failed for dev "
>  				    "%x:%x\n", op.bus, op.devfn);