[Qemu-devel] Re: [PATCH 1/2] pci: Automatically patch PCI vendor id and device id in PCI ROM

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

On Tue, Oct 19, 2010 at 11:08:21PM +0200, Stefan Weil wrote:
> PCI devices with different vendor or device ids sometimes share
> the same rom code. Only the ids and the checksum
> differs in a boot rom for such devices.
> 
> The i825xx ethernet controller family is a typical example
> which is implemented in hw/eepro100.c. It uses at least
> 3 different device ids, so normally 3 boot roms would be needed.
> 
> By automatically patching vendor id and device id (and the checksum)
> in qemu, all emulated family members can share the same boot rom.
> 
> VGA bios roms are another example with different vendor and device ids.
> 
> Only qemu's built-in default rom files will be patched.
> 
> v2:
>     * Patch also the vendor id (and remove the sanity check for vendor id).
> 
> v3:
>     * Don't patch a rom file when its name was set by the user.
>       Thus we avoid modifications of unknown rom data.
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Markus Armbruster <armbru@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Stefan Weil <weil@mail.berlios.de>

Looks safe enough for me.
Applied.

> ---
>  hw/pci.c |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 files changed, 69 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 1280d4d..74cbea5 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -78,7 +78,7 @@ static struct BusInfo pci_bus_info = {
>  
>  static void pci_update_mappings(PCIDevice *d);
>  static void pci_set_irq(void *opaque, int irq_num, int level);
> -static int pci_add_option_rom(PCIDevice *pdev);
> +static int pci_add_option_rom(PCIDevice *pdev, bool is_default_rom);
>  static void pci_del_option_rom(PCIDevice *pdev);
>  
>  static uint16_t pci_default_sub_vendor_id = PCI_SUBVENDOR_ID_REDHAT_QUMRANET;
> @@ -1672,6 +1672,7 @@ static int pci_qdev_init(DeviceState *qdev, DeviceInfo *base)
>      PCIDeviceInfo *info = container_of(base, PCIDeviceInfo, qdev);
>      PCIBus *bus;
>      int devfn, rc;
> +    bool is_default_rom;
>  
>      /* initialize cap_present for pci_is_express() and pci_config_size() */
>      if (info->is_express) {
> @@ -1692,9 +1693,12 @@ static int pci_qdev_init(DeviceState *qdev, DeviceInfo *base)
>      }
>  
>      /* rom loading */
> -    if (pci_dev->romfile == NULL && info->romfile != NULL)
> +    is_default_rom = false;
> +    if (pci_dev->romfile == NULL && info->romfile != NULL) {
>          pci_dev->romfile = qemu_strdup(info->romfile);
> -    pci_add_option_rom(pci_dev);
> +        is_default_rom = true;
> +    }
> +    pci_add_option_rom(pci_dev, is_default_rom);
>  
>      if (qdev->hotplugged) {
>          rc = bus->hotplug(bus->hotplug_qdev, pci_dev, 1);
> @@ -1797,8 +1801,64 @@ static void pci_map_option_rom(PCIDevice *pdev, int region_num, pcibus_t addr, p
>      cpu_register_physical_memory(addr, size, pdev->rom_offset);
>  }
>  
> +/* Patch the PCI vendor and device ids in a PCI rom image if necessary.
> +   This is needed for an option rom which is used for more than one device. */
> +static void pci_patch_ids(PCIDevice *pdev, uint8_t *ptr, int size)
> +{
> +    uint16_t vendor_id;
> +    uint16_t device_id;
> +    uint16_t rom_vendor_id;
> +    uint16_t rom_device_id;
> +    uint16_t rom_magic;
> +    uint16_t pcir_offset;
> +    uint8_t checksum;
> +
> +    /* Words in rom data are little endian (like in PCI configuration),
> +       so they can be read / written with pci_get_word / pci_set_word. */
> +
> +    /* Only a valid rom will be patched. */
> +    rom_magic = pci_get_word(ptr);
> +    if (rom_magic != 0xaa55) {
> +        PCI_DPRINTF("Bad ROM magic %04x\n", rom_magic);
> +        return;
> +    }
> +    pcir_offset = pci_get_word(ptr + 0x18);
> +    if (pcir_offset + 8 >= size || memcmp(ptr + pcir_offset, "PCIR", 4)) {
> +        PCI_DPRINTF("Bad PCIR offset 0x%x or signature\n", pcir_offset);
> +        return;
> +    }
> +
> +    vendor_id = pci_get_word(pdev->config + PCI_VENDOR_ID);
> +    device_id = pci_get_word(pdev->config + PCI_DEVICE_ID);
> +    rom_vendor_id = pci_get_word(ptr + pcir_offset + 4);
> +    rom_device_id = pci_get_word(ptr + pcir_offset + 6);
> +
> +    PCI_DPRINTF("%s: ROM id %04x%04x / PCI id %04x%04x\n", pdev->romfile,
> +                vendor_id, device_id, rom_vendor_id, rom_device_id);
> +
> +    checksum = ptr[6];
> +
> +    if (vendor_id != rom_vendor_id) {
> +        /* Patch vendor id and checksum (at offset 6 for etherboot roms). */
> +        checksum += (uint8_t)rom_vendor_id + (uint8_t)(rom_vendor_id >> 8);
> +        checksum -= (uint8_t)vendor_id + (uint8_t)(vendor_id >> 8);
> +        PCI_DPRINTF("ROM checksum %02x / %02x\n", ptr[6], checksum);
> +        ptr[6] = checksum;
> +        pci_set_word(ptr + pcir_offset + 4, vendor_id);
> +    }
> +
> +    if (device_id != rom_device_id) {
> +        /* Patch device id and checksum (at offset 6 for etherboot roms). */
> +        checksum += (uint8_t)rom_device_id + (uint8_t)(rom_device_id >> 8);
> +        checksum -= (uint8_t)device_id + (uint8_t)(device_id >> 8);
> +        PCI_DPRINTF("ROM checksum %02x / %02x\n", ptr[6], checksum);
> +        ptr[6] = checksum;
> +        pci_set_word(ptr + pcir_offset + 6, device_id);
> +    }
> +}
> +
>  /* Add an option rom for the device */
> -static int pci_add_option_rom(PCIDevice *pdev)
> +static int pci_add_option_rom(PCIDevice *pdev, bool is_default_rom)
>  {
>      int size;
>      char *path;
> @@ -1849,6 +1909,11 @@ static int pci_add_option_rom(PCIDevice *pdev)
>      load_image(path, ptr);
>      qemu_free(path);
>  
> +    if (is_default_rom) {
> +        /* Only the default rom images will be patched (if needed). */
> +        pci_patch_ids(pdev, ptr, size);
> +    }
> +
>      pci_register_bar(pdev, PCI_ROM_SLOT, size,
>                       0, pci_map_option_rom);
>  
> -- 
> 1.7.1