Re: [PATCH v2 2/2] pci: add romsize property

[Laszlo Ersek]

On 02/02/21 11:05, David Edmondson wrote:
> On Friday, 2021-01-29 at 20:28:38 +01, Paolo Bonzini wrote:
> 
>> This property can be useful for distros to set up known-good ROM sizes for
>> migration purposes.  The VM will fail to start if the ROM is too large,
>> and migration compatibility will not be broken if the ROM is too small.
>>
>> Note that even though romsize is a uint32_t, it has to be between 1
>> (because empty ROM files are not accepted, and romsize must be greater
>> than the file) and 2^31 (because values above are not powers of two and
>> are rejected).
>>
>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Reviewed-by: Peter Xu <peterx@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>  hw/pci/pci.c             | 19 +++++++++++++++++--
>>  hw/xen/xen_pt_load_rom.c | 14 ++++++++++++--
>>  include/hw/pci/pci.h     |  1 +
>>  3 files changed, 30 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index bbce10050b..5b3fe3c294 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -68,6 +68,7 @@ static void pcibus_reset(BusState *qbus);
>>  static Property pci_props[] = {
>>      DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
>>      DEFINE_PROP_STRING("romfile", PCIDevice, romfile),
>> +    DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, -1),
>>      DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, 1),
>>      DEFINE_PROP_BIT("multifunction", PCIDevice, cap_present,
>>                      QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
>> @@ -2107,6 +2108,11 @@ static void pci_qdev_realize(DeviceState *qdev, Error 
>> **errp)
>>      bool is_default_rom;
>>      uint16_t class_id;
>>  
>> +    if (pci_dev->romsize != -1 && !is_power_of_2(pci_dev->romsize)) {
>> +        error_setg(errp, "ROM size %d is not a power of two", 
>> pci_dev->romsize);
>> +        return;
> 
> It would be nice to be consistent with the format type when reporting
> errors - it's %d here...
> 
>> +    }
>> +
>>      /* initialize cap_present for pci_is_express() and pci_config_size(),
>>       * Note that hybrid PCIs are not set automatically and need to manage
>>       * QEMU_PCI_CAP_EXPRESS manually */
>> @@ -2372,7 +2378,16 @@ static void pci_add_option_rom(PCIDevice *pdev, bool 
>> is_default_rom,
>>          g_free(path);
>>          return;
>>      }
>> -    size = pow2ceil(size);
>> +    if (pdev->romsize != -1) {
>> +        if (size > pdev->romsize) {
>> +            error_setg(errp, "romfile \"%s\" (%u bytes) is too large for 
>> ROM size %u",
>> +                       pdev->romfile, (uint32_t)size, pdev->romsize);
> 
> %u here...
> 
>> +            g_free(path);
>> +            return;
>> +        }
>> +    } else {
>> +        pdev->romsize = pow2ceil(size);
>> +    }
>>  
>>      vmsd = qdev_get_vmsd(DEVICE(pdev));
>>  
>> @@ -2382,7 +2397,7 @@ static void pci_add_option_rom(PCIDevice *pdev, bool 
>> is_default_rom,
>>          snprintf(name, sizeof(name), "%s.rom", 
>> object_get_typename(OBJECT(pdev)));
>>      }
>>      pdev->has_rom = true;
>> -    memory_region_init_rom(&pdev->rom, OBJECT(pdev), name, size, 
>> &error_fatal);
>> +    memory_region_init_rom(&pdev->rom, OBJECT(pdev), name, pdev->romsize, 
>> &error_fatal);
>>      ptr = memory_region_get_ram_ptr(&pdev->rom);
>>      if (load_image_size(path, ptr, size) < 0) {
>>          error_setg(errp, "failed to load romfile \"%s\"", pdev->romfile);
>> diff --git a/hw/xen/xen_pt_load_rom.c b/hw/xen/xen_pt_load_rom.c
>> index a50a80837e..153812f8cd 100644
>> --- a/hw/xen/xen_pt_load_rom.c
>> +++ b/hw/xen/xen_pt_load_rom.c
>> @@ -53,10 +53,20 @@ void *pci_assign_dev_load_option_rom(PCIDevice *dev,
>>      }
>>      fseek(fp, 0, SEEK_SET);
>>  
>> +    if (dev->romsize != -1) {
>> +        if (st.st_size > dev->romsize) {
>> +            error_report("ROM BAR \"%s\" (%ld bytes) is too large for ROM 
>> size %d",
> 
> %d here...
> 
>> +                         rom_file, (long) st.st_size, dev->romsize);
>> +            goto close_rom;
>> +        }
>> +    } else {
>> +        dev->romsize = st.st_size;
>> +    }
>> +
>>      snprintf(name, sizeof(name), "%s.rom", object_get_typename(owner));
>> -    memory_region_init_ram(&dev->rom, owner, name, st.st_size, 
>> &error_abort);
>> +    memory_region_init_ram(&dev->rom, owner, name, dev->romsize, 
>> &error_abort);
>>      ptr = memory_region_get_ram_ptr(&dev->rom);
>> -    memset(ptr, 0xff, st.st_size);
>> +    memset(ptr, 0xff, dev->romsize);
>>  
>>      if (!fread(ptr, 1, st.st_size, fp)) {
>>          error_report("pci-assign: Cannot read from host %s", rom_file);
>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>> index 259f9c992d..b028245b62 100644
>> --- a/include/hw/pci/pci.h
>> +++ b/include/hw/pci/pci.h
>> @@ -343,6 +343,7 @@ struct PCIDevice {
>>  
>>      /* Location of option rom */
>>      char *romfile;
>> +    uint32_t romsize;
>>      bool has_rom;
>>      MemoryRegion rom;
>>      uint32_t rom_bar;
>> -- 
>> 2.29.2
> 
> dme.
> 

I believe this may be worth a v3; for that:

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo