Re: [Qemu-devel] [PATCH] qemu: improve hugepage allocation failure message

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/01/2018 21:16, Haozhong Zhang wrote:
> On 01/09/18 17:37 -0200, Marcelo Tosatti wrote:
>>
>> Improve hugepage allocation failure message, indicating
>> whats happening to the user.
>>
>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>
>> diff --git a/exec.c b/exec.c
>> index 4722e521d4..439abedb98 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -1643,7 +1643,8 @@ static void *file_ram_alloc(RAMBlock *block,
>>                           block->flags & RAM_SHARED);
>>      if (area == MAP_FAILED) {
>>          error_setg_errno(errp, errno,
>> -                         "unable to map backing store for guest RAM");
>> +                         "unable to map backing store for guest RAM, "
>> +                         "falling back to malloc based RAM allocation");
>>          return NULL;
>>      }
>>  
> 
> The backing store here is not always hugetlbfs, e.g., it can be NVDIMM
> and even regular files. In those cases, the failure of file_ram_alloc()
> does not fall back to malloc.

It's also not happending if !mem_prealloc.  Let's instead add an
error_report in allocate_system_memory_nonnuma (and it's probably better
to use MAP_ANON instead of malloc in the message).

Paolo