On 2/26/21 9:23 AM, David Edmondson wrote:
> On Friday, 2021-02-26 at 00:02:38 +01, Philippe Mathieu-Daudé wrote:
>
>> If the block drive is read-only we will model a "protected" flash
>> device. We can thus use memory_region_init_rom_device_from_file()
>> which mmap the backing file when creating the MemoryRegion.
>> If the same backing file is used by multiple QEMU instances, this
>> reduces the memory footprint (this is often the case with the
>> CODE flash image from OVMF and AAVMF).
>>
>> Suggested-by: Stefan Hajnoczi <stefa...@redhat.com>
>> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
>> ---
>> hw/block/pflash_cfi01.c | 20 ++++++++++++++------
>> hw/block/pflash_cfi02.c | 18 ++++++++++++++----
>> 2 files changed, 28 insertions(+), 10 deletions(-)
>>
>> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
>> index a5fa8d8b74a..5757391df1c 100644
>> --- a/hw/block/pflash_cfi01.c
>> +++ b/hw/block/pflash_cfi01.c
>> @@ -743,11 +743,19 @@ static void pflash_cfi01_realize(DeviceState *dev,
>> Error **errp)
>> pfl->ro = 0;
>> }
>>
>> - memory_region_init_rom_device(
>> - &pfl->mem, OBJECT(dev),
>> - &pflash_cfi01_ops,
>> - pfl,
>> - pfl->name, total_len, errp);
>> + if (pfl->blk && pfl->ro) {
>> + memory_region_init_rom_device_from_file(&pfl->mem, OBJECT(dev),
>> + &pflash_cfi01_ops, pfl,
>> + pfl->name, total_len,
>> + qemu_real_host_page_size,
>> + RAM_SHARED,
>> + blk_bs(pfl->blk)->filename,
>
> How will this behave if someone does:
>
> -drive file=OVMF_CODE.fd.qcow2,index=0,if=pflash,format=qcow2,readonly=on
>
> Honestly, I'm not sure why they would, but it works today.
OK I can add a check for "raw" driver, but I don't know to check for
offset == 0.
