Re: [Qemu-devel] [PATCH] Permit zero-sized qemu_malloc() & friends

[Avi Kivity <avi@redhat.com>]

On 12/06/2009 08:12 PM, malc wrote:
>
>> Init is pretty easy to handle.  I'm worried about runtime where you can't
>> report an error to the guest.  Real hardware doesn't oom.
>>      
> Here, i do agree, but mostly because most of the users of allocation
> functions just themselves returned NULL or -1 or whatever and never
> really bothered to report anything, so the addition of OOM check that
> you've added made the code less cluttered.
>    

My point is that it would take a major rework, and would probably 
involve removing the allocations instead of handling any errors.  For 
example, a scsi device would tell the block device the upper bound of 
aiocbs it could possibly issue, and the maximum number of sg elements in 
a request, and qcow2 (or any other backing format driver) would 
preallocate enough resources to satisfy the worst case.  And we still 
can't handle a syscall returning ENOMEM.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.