On 09/18/20 15:41, Philippe Mathieu-Daudé wrote:
> Cc'ing firmware experts.
>
> On 9/18/20 2:26 PM, haibinzhang(寮犳捣鏂�) wrote:
>> Default size of arm-virt pflash image is 64MB which
>> will cost extra 128MB(64MBx2) memory per qemu process
>> and 12.5GB for 100 qemu processes. Host memory is
>> precious and it is valuable to reduce pflash image size.
>> For compatibility arm-virt uses real size when mapping.
>
> Flash#0 is a device because eventually its model will handle
> sector/block protection, so firmware can do CapsuleUpdate
> (updating itself). Meanwhile you could treat flash#0 as a pure
> ROM device... But this wouldn't be the 'arm-virt' machine anymore.
>
>>
>> Signed-off-by: Haibin Zhang <haibinzh...@tencent.com>
>> ---
>> hw/arm/virt.c | 22 ++++++++++++++++++++--
>> 1 file changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index acf9bfbece..3545e12865 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -50,6 +50,7 @@
>> #include "sysemu/sysemu.h"
>> #include "sysemu/tpm.h"
>> #include "sysemu/kvm.h"
>> +#include "sysemu/block-backend.h"
>> #include "hw/loader.h"
>> #include "exec/address-spaces.h"
>> #include "qemu/bitops.h"
>> @@ -1001,10 +1002,27 @@ static void virt_flash_map(VirtMachineState *vms,
>> */
>> hwaddr flashsize = vms->memmap[VIRT_FLASH].size / 2;
>> hwaddr flashbase = vms->memmap[VIRT_FLASH].base;
>> + int64_t realsize;
>> + BlockBackend *blk;
>>
>> - virt_flash_map1(vms->flash[0], flashbase, flashsize,
>> + realsize = flashsize;
>> + blk = pflash_cfi01_get_blk(vms->flash[0]);
>> + if (blk) {
>> + realsize = blk_getlength(blk);
>> + realsize = realsize < flashsize ? realsize : flashsize;
>> + }
>
> Stefan recently posted "nvdimm: read-only file support" which
> might be a better way to achieve what you want:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg741137.html
>
>> +
>> + virt_flash_map1(vms->flash[0], flashbase, realsize,
>> secure_sysmem);
>> - virt_flash_map1(vms->flash[1], flashbase + flashsize, flashsize,
>> +
>> + realsize = flashsize;
>> + blk = pflash_cfi01_get_blk(vms->flash[1]);
>> + if (blk) {
>> + realsize = blk_getlength(blk);
>> + realsize = realsize < flashsize ? realsize : flashsize;
>> + }
>> +
>> + virt_flash_map1(vms->flash[1], flashbase + flashsize, realsize,
>> sysmem);
>> }
>>
>> --
>> 2.23.0
>>
>
We've been here before.
[Qemu-devel] [RFC PATCH] hw/arm/virt: use variable size of flash device to
save memory
https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg06773.html
http://mid.mail-archive.com/20190325125142.11628-1-zhengxiang9@huawei.com
I don't have anything to add.
Laszlo
