Re: [Qemu-devel] [PATCH] exec.c: workaround regression caused by alignment change in d2f39ad

[Christian Borntraeger]

On 10/24/2016 02:58 PM, Paolo Bonzini wrote:
> 
> 
> On 24/10/2016 14:49, Haozhong Zhang wrote:
>> Commit d2f39ad "exec.c: Ensure right alignment also for file backed ram"
>> added an additional alignment requirement on the size of backend file
>> besides the previous page size. On x86, the alignment is changed from
>> 4KB in QEMU 2.6 to 2MB in QEMU 2.7.
>>
>> This change breaks certain usages in QEMU 2.7 on x86, e.g.
>>     -object memory-backend-file,id=mem1,mem-path=/tmp/,size=$SZ
>>     -device pc-dimm,id=dimm1,memdev=mem1
>> where $SZ is multiple of 4KB but not 2MB (e.g. 1023M). QEMU 2.7
>> reports the following error message and aborts:
>> qemu-system-x86_64: -device pc-dimm,memdev=mem1,id=nv1: backend memory size 
>> must be multiple of 0x200000
>>
>> The same regression may also happen in other platforms as indicated by
>> Igor Mammedov. This change is however necessary for s390 according to
>> the commit message of d2f39ad, so we workaround the regression by taking
>> the change only on s390.
>>
>> Signed-off-by: Haozhong Zhang <address@hidden>
>> Reported-by: "Xu, Anthony" <address@hidden>
>> ---
>>  exec.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/exec.c b/exec.c
>> index e63c5a1..55915ea 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -1254,7 +1254,11 @@ static void *file_ram_alloc(RAMBlock *block,
>>      }
>>  
>>      block->page_size = qemu_fd_getpagesize(fd);
>> +#if defined(__s390x__)
>>      block->mr->align = MAX(block->page_size, QEMU_VMALLOC_ALIGN);
>> +#else
>> +    block->mr->align = block->page_size;
>> +#endif
> 
> Better:
> 
>       block->mr->align = block->page_size;
> #ifdef __s390x__
>       if (kvm_enabled()) {
>           block->mr->align = MAX(block->mr->align, QEMU_VMALLOC_ALIGN);
>       }
> #endif
> 
> Queued with this change.

Thanks.
Acked-by: Christian Borntraeger <address@hidden>

> 
> Paolo
> 
>>  
>>      if (memory < block->page_size) {
>>          error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
>>
> 
>