Re: [Qemu-devel] [PATCH v2 3/6] pci: Fix the wrong return value judgment condition

[Marcel Apfelbaum <marcel@redhat.com>]

On 02/06/2017 10:54, Mao Zhongyi wrote:
> On success, pci_add_capability2() returns a positive value. On
> failure, it sets an error and return a negative value. It doesn't
> always return 0. So the judgment condtion of pci_add_capability2()
> is wrong if it contains the situation where return value equal to
> 0. Fix the error checks from its callers.
> 

Hi,
I would suggest changing the above to a simpler:

pci_add_capability returns a strictly positive value on success,
correct asserts.

Thanks,
Marcel

> Cc: dmitry@daynix.com
> Cc: jasowang@redhat.com
> Cc: alex.williamson@redhat.com
> Cc: marcel@redhat.com
> Cc: mst@redhat.com
> Cc: armbru@redhat.com
> Signed-off-by: Mao Zhongyi <maozy.fnst@cn.fujitsu.com>
> ---
>   hw/net/e1000e.c   | 2 +-
>   hw/net/eepro100.c | 2 +-
>   hw/vfio/pci.c     | 2 +-
>   3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/net/e1000e.c b/hw/net/e1000e.c
> index 6e23493..8259d67 100644
> --- a/hw/net/e1000e.c
> +++ b/hw/net/e1000e.c
> @@ -374,7 +374,7 @@ e1000e_add_pm_capability(PCIDevice *pdev, uint8_t offset, uint16_t pmc)
>   {
>       int ret = pci_add_capability(pdev, PCI_CAP_ID_PM, offset, PCI_PM_SIZEOF);
>   
> -    if (ret >= 0) {
> +    if (ret > 0) {
>           pci_set_word(pdev->config + offset + PCI_PM_PMC,
>                        PCI_PM_CAP_VER_1_1 |
>                        pmc);
> diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
> index 4bf71f2..da36816 100644
> --- a/hw/net/eepro100.c
> +++ b/hw/net/eepro100.c
> @@ -571,7 +571,7 @@ static void e100_pci_reset(EEPRO100State * s)
>           int cfg_offset = 0xdc;
>           int r = pci_add_capability(&s->dev, PCI_CAP_ID_PM,
>                                      cfg_offset, PCI_PM_SIZEOF);
> -        assert(r >= 0);
> +        assert(r > 0);
>           pci_set_word(pci_conf + cfg_offset + PCI_PM_PMC, 0x7e21);
>   #if 0 /* TODO: replace dummy code for power management emulation. */
>           /* TODO: Power Management Control / Status. */
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 32aca77..5881968 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -1744,7 +1744,7 @@ static int vfio_setup_pcie_cap(VFIOPCIDevice *vdev, int pos, uint8_t size,
>       }
>   
>       pos = pci_add_capability(&vdev->pdev, PCI_CAP_ID_EXP, pos, size);
> -    if (pos >= 0) {
> +    if (pos > 0) {
>           vdev->pdev.exp.exp_cap = pos;
>       }
>   
>