Re: [PATCH] PCI: designware: Fix dw_handle_msi_irq() on 64-bit BE configs

[Joao Pinto <Joao.Pinto@synopsys.com>]

Hi Ben,

Às 12:46 AM de 7/21/2017, Ben Hutchings escreveu:
> Commit 1b497e6493c4 "PCI: dwc: Fix uninitialized variable in
> dw_handle_msi_irq()" fixed one problem for 64-bit architectures but
> left another.  The find_next_bit() function assumes native ordering of
> bits within each word (unsigned long), so passing a pointer to a u32
> variable will cause it to scan the following 32 bits on a 64-bit
> big-endian configuration.  Alternately it could result in an alignment
> fault on some architectures.
> 
> Copy the status to an unsigned long variable before using
> find_next_bit().
> 
> Fixes: 1b497e6493c4 ("PCI: dwc: Fix uninitialized variable in ...")
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
> This is compile-tested only.
> 
> Ben.
> 
>  drivers/pci/dwc/pcie-designware-host.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
> index d29c020da082..511fc9188f98 100644
> --- a/drivers/pci/dwc/pcie-designware-host.c
> +++ b/drivers/pci/dwc/pcie-designware-host.c
> @@ -57,6 +57,7 @@ static struct irq_chip dw_msi_irq_chip = {
>  irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
>  {
>  	u32 val;
> +	unsigned long bits;

Could you please declare the variable in a ordered fashion (after "int i, pos,
irq;")? I suggest to change the variable name to "status" and val would be a
temporary variable only.

>  	int i, pos, irq;
>  	irqreturn_t ret = IRQ_NONE;
>  
> @@ -65,11 +66,11 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
>  				    &val);
>  		if (!val)
>  			continue;
> +		bits = val;
>  
>  		ret = IRQ_HANDLED;
>  		pos = 0;
> -		while ((pos = find_next_bit((unsigned long *) &val, 32,
> -					    pos)) != 32) {
> +		while ((pos = find_next_bit(&bits, 32, pos)) != 32) {
>  			irq = irq_find_mapping(pp->irq_domain, i * 32 + pos);
>  			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12,
>  					    4, 1 << pos);
> 

Thanks,
Joao