Re: [PATCH] dev-assignment: handle device with incorrect PCIe Cap structure size

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jul 26, 2011 at 06:08:09PM -0400, Donald Dutile wrote:
> The bcm5761 provides a PCIe Cap structure (capid=0x10)
> that is invalid, providing one that is 8 bytes shorter
> than the v2 PCIe spec defines.
> This leads to a memory corruption when mapped for device-assigment.
> 
> Add a check in assigned_device_pci_cap_init() to correct
> this hw error for this device, and try to catch other ones
> and print warnings if they exists.
> 
> Signed-off-by: Donald Dutile <ddutile@redhat.com>
> cc: Alex Williamson <alex.williamson@redhat.com>
> cc: Michael S. Tsirking <mst@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> 
>  hw/device-assignment.c |   29 ++++++++++++++++++++++++-----
>  1 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/device-assignment.c b/hw/device-assignment.c
> index 36ad6b0..e073840 100644
> --- a/hw/device-assignment.c
> +++ b/hw/device-assignment.c
> @@ -1419,18 +1419,37 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>      }
>  
>      if ((pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_EXP, 0))) {
> -        uint8_t version;
> +        uint8_t version, size;
>          uint16_t type, devctl, lnkcap, lnksta;
>          uint32_t devcap;
> -        int size = 0x3c; /* version 2 size */
>  
>          version = pci_get_byte(pci_dev->config + pos + PCI_EXP_FLAGS);
>          version &= PCI_EXP_FLAGS_VERS;
>          if (version == 1) {
>              size = 0x14;
> -        } else if (version > 2) {
> -            fprintf(stderr, "Unsupported PCI express capability version %d\n",
> -                    version);
> +        } else if (version == 2) {
> +            /*
> +             * Check for non-std size, accept reduced size to 0x34,
> +             * which is what bcm5761 implemented, violating the 
> +             * PCIe v3.0 spec that regs should exist and be read as 0,
> +             * not optionally provided and shorten the struct size.
> +             */
> +            size = MIN(0x3c, PCI_CONFIG_SPACE_SIZE - pos);
> +            if (size < 0x34) {
> +                fprintf(stderr,
> +                        "%s: Invalid size PCIe cap-id 0x%x \n",
> +                        __func__, PCI_CAP_ID_EXP);
> +                return -EINVAL;
> +            } else if (size != 0x3c) {
> +                fprintf(stderr,
> +                        "WARNING, %s: PCIe cap-id 0x%x has "
> +                        "non-standard size 0x%x; std size should be 0x3c \n",
> +                         __func__, PCI_CAP_ID_EXP, size);
> +            } 
> +        } else {
> +            fprintf(stderr, 
> +                    "%s: Unsupported PCI express capability version %d\n",
> +                    __func__, version);
>              return -EINVAL;
>          }
>