Re: [Qemu-devel] [PATCH 2/2 v2] vfio: blacklist loading of unstable roms

[Alex Williamson]

On Wed, 2014-02-19 at 15:20 -0500, Bandan Das wrote:
> Certain cards such as the Broadcom BCM57810 have rom quirks
> that exhibit unstable system behavior duing device assignment. In
> the particular case of 57810, rom execution hangs and if a FLR
> follows, the device becomes inoperable until a power cycle. This
> is a simple change to blacklist loading of rom for such cards
> unless the user specifies a romfile or rombar=1 on the cmd line
> 
> Signed-off-by: Bandan Das <address@hidden>
> ---
>  hw/misc/vfio.c | 58 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> index 8db182f..58f348e 100644
> --- a/hw/misc/vfio.c
> +++ b/hw/misc/vfio.c
> @@ -209,6 +209,16 @@ typedef struct VFIOGroup {
>      QLIST_ENTRY(VFIOGroup) container_next;
>  } VFIOGroup;
>  
> +typedef struct VFIORomBlacklistEntry {
> +    uint16_t vendor_id;
> +    uint16_t device_id;
> +} VFIORomBlacklistEntry;
> +
> +static const VFIORomBlacklistEntry romblacklist[] = {
> +    /* Broadcom BCM 57810 */
> +    { 0x14e4, 0x168e }
> +};
> +

Ideally we'd want to be able to reference a bugzilla here so we have
some reference in the code to track developments.  Also, can we capture
the ROM version known to cause this problem so if somebody later says
that it works we can have something to compare?  The PCI firmware spec
defines the data structure.  Effectively you can dump the ROM from the
device, run xxd on it and look for the "PCIR" string that defines the
start of the PCI data structure.  The 2 bytes at offset 12h (where 0h is
the 'P' in "PCIR") have a revision level field.

>  #define MSIX_CAP_LENGTH 12
>  
>  static QLIST_HEAD(, VFIOContainer)
> @@ -1197,6 +1207,26 @@ static const MemoryRegionOps vfio_rom_ops = {
>      .endianness = DEVICE_LITTLE_ENDIAN,
>  };
>  
> +static bool vfio_blacklist_opt_rom(VFIODevice *vdev)
> +{
> +    PCIDevice *pdev = &vdev->pdev;
> +    uint16_t vendor_id, device_id;
> +    int count = 0;
> +
> +    vendor_id = pci_get_word(pdev->config + PCI_VENDOR_ID);
> +    device_id = pci_get_word(pdev->config + PCI_DEVICE_ID);
> +
> +    while (count < ARRAY_SIZE(romblacklist)) {
> +        if (romblacklist[count].vendor_id == vendor_id &&
> +            romblacklist[count].device_id == device_id) {
> +                return true;
> +        }
> +        count++;
> +    }
> +
> +    return false;
> +}
> +
>  static void vfio_pci_size_rom(VFIODevice *vdev)
>  {
>      uint32_t orig, size = cpu_to_le32((uint32_t)PCI_ROM_ADDRESS_MASK);
> @@ -1204,9 +1234,37 @@ static void vfio_pci_size_rom(VFIODevice *vdev)
>      char name[32];
>  
>      if (vdev->pdev.romfile || !vdev->pdev.rom_bar) {
> +        /* Since pci handles romfile, just print a message and return */
> +        if (vfio_blacklist_opt_rom(vdev) && vdev->pdev.romfile) {
> +            error_printf("Warning : Device at %04x:%02x:%02x.%x "
> +                         "is known to cause system instability issues during 
> "
> +                         "option rom execution. "
> +                         "Proceeding anyway since user specified romfile\n",
> +                         vdev->host.domain, vdev->host.bus, vdev->host.slot,
> +                         vdev->host.function);
> +        }
>          return;
>      }
>  
> +    if (vfio_blacklist_opt_rom(vdev) && vdev->pdev.rom_bar) {
> +        if (vdev->pdev.rom_bar == 1) {
> +            error_printf("Warning : Device at %04x:%02x:%02x.%x "
> +                         "is known to cause system instability issues during 
> "
> +                         "option rom execution. "
> +                         "Proceeding anyway since user specified rombar=1\n",
> +                         vdev->host.domain, vdev->host.bus, vdev->host.slot,
> +                         vdev->host.function);
> +        } else {
> +            error_printf("Warning : Rom loading for device at "
> +                         "%04x:%02x:%02x.%x has been disabled due to "
> +                         "system instability issues. "
> +                         "Specify rombar=1 or romfile to force\n",
> +                         vdev->host.domain, vdev->host.bus, vdev->host.slot,
> +                         vdev->host.function);
> +            return;
> +        }
> +    }
> +

What happens if this card, or some later user of this blacklisting, has
SKUs that don't have a ROM?  Aren't we going to print this last warning
regardless of whether we found anything to load?  Just shifting this
whole block down below the next couple tests is probably sufficient.
Thanks,

Alex

>      /*
>       * Use the same size ROM BAR as the physical device.  The contents
>       * will get filled in later when the guest tries to read it.