Re: [patch 33/39] PCI/MSI: Sanitize MSI-X checks

[Bjorn Helgaas]

On Fri, Nov 11, 2022 at 02:55:07PM +0100, Thomas Gleixner wrote:
> There is no point in doing the same sanity checks over and over in a loop
> during MSI-X enablement. Put them in front of the loop and return early
> when they fail.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

> ---
>  drivers/pci/msi/msi.c |   67 +++++++++++++++++++++++++-------------------------
>  1 file changed, 34 insertions(+), 33 deletions(-)
> 
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -721,47 +721,31 @@ static int msix_capability_init(struct p
>  	return ret;
>  }
>  
> -static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
> -			     int nvec, struct irq_affinity *affd, int flags)
> +static bool pci_msix_validate_entries(struct msix_entry *entries, int nvec, int hwsize)
>  {
> -	int nr_entries;
>  	int i, j;
>  
> -	if (!pci_msi_supported(dev, nvec) || dev->current_state != PCI_D0)
> -		return -EINVAL;
> +	if (!entries)
> +		return true;
>  
> -	nr_entries = pci_msix_vec_count(dev);
> -	if (nr_entries < 0)
> -		return nr_entries;
> -	if (nvec > nr_entries && !(flags & PCI_IRQ_VIRTUAL))
> -		return nr_entries;
> -
> -	if (entries) {
> -		/* Check for any invalid entries */
> -		for (i = 0; i < nvec; i++) {
> -			if (entries[i].entry >= nr_entries)
> -				return -EINVAL;		/* invalid entry */
> -			for (j = i + 1; j < nvec; j++) {
> -				if (entries[i].entry == entries[j].entry)
> -					return -EINVAL;	/* duplicate entry */
> -			}
> +	for (i = 0; i < nvec; i++) {
> +		/* Entry within hardware limit? */
> +		if (entries[i].entry >= hwsize)
> +			return false;
> +
> +		/* Check for duplicate entries */
> +		for (j = i + 1; j < nvec; j++) {
> +			if (entries[i].entry == entries[j].entry)
> +				return false;
>  		}
>  	}
> -
> -	/* Check whether driver already requested for MSI IRQ */
> -	if (dev->msi_enabled) {
> -		pci_info(dev, "can't enable MSI-X (MSI IRQ already assigned)\n");
> -		return -EINVAL;
> -	}
> -	return msix_capability_init(dev, entries, nvec, affd);
> +	return true;
>  }
>  
> -int __pci_enable_msix_range(struct pci_dev *dev,
> -			    struct msix_entry *entries, int minvec,
> -			    int maxvec, struct irq_affinity *affd,
> -			    int flags)
> +int __pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries, int minvec,
> +			    int maxvec, struct irq_affinity *affd, int flags)
>  {
> -	int rc, nvec = maxvec;
> +	int hwsize, rc, nvec = maxvec;
>  
>  	if (maxvec < minvec)
>  		return -ERANGE;
> @@ -774,6 +758,23 @@ int __pci_enable_msix_range(struct pci_d
>  	if (WARN_ON_ONCE(dev->msix_enabled))
>  		return -EINVAL;
>  
> +	if (!pci_msi_supported(dev, nvec) || dev->current_state != PCI_D0)
> +		return -EINVAL;
> +
> +	hwsize = pci_msix_vec_count(dev);
> +	if (hwsize < 0)
> +		return hwsize;
> +
> +	if (!pci_msix_validate_entries(entries, nvec, hwsize))
> +		return -EINVAL;
> +
> +	/* PCI_IRQ_VIRTUAL is a horrible hack! */
> +	if (nvec > hwsize && !(flags & PCI_IRQ_VIRTUAL))
> +		nvec = hwsize;
> +
> +	if (nvec < minvec)
> +		return -ENOSPC;
> +
>  	rc = pci_setup_msi_context(dev);
>  	if (rc)
>  		return rc;
> @@ -785,7 +786,7 @@ int __pci_enable_msix_range(struct pci_d
>  				return -ENOSPC;
>  		}
>  
> -		rc = __pci_enable_msix(dev, entries, nvec, affd, flags);
> +		rc = msix_capability_init(dev, entries, nvec, affd);
>  		if (rc == 0)
>  			return nvec;
>  
>