Re: [Qemu-devel] [qemu-s390x] [PATCH v4 2/2] s390x: Enable KVM huge page backing support

[Thomas Huth]

On 08/02/2018 08:53 AM, Janosch Frank wrote:
> On 01.08.2018 18:47, Thomas Huth wrote:
>> On 08/01/2018 03:19 PM, Janosch Frank wrote:
>>> +static int kvm_s390_configure_mempath_backing(KVMState *s)
>>> +{
>>> +    size_t path_psize = qemu_mempath_getpagesize(mem_path);
>>> +
>>> +    if (path_psize == 4 * KiB)
>>> +        return 0;
>>
>> Missing curly braces.
> 
> urgh, right, this is not the kernel.
> 
>>
>>> +    if (path_psize != 1 * MiB) {
>>> +        error_report("Memory backing with 2G pages was specified, "
>>> +                     "but KVM does not support this memory backing");
>>
>> May I suggest to use a text that rather matches the condition of the
>> if-statement (just in case there will be other sizes in the future...),
>> e.g. "Memory backing is only supported for 1 MiB huge pages" or
>> something similar.
>>
>>  Thomas
>>
> 
> That's actually the gist of it. s390 supports 4k, 1M and 2G and looking
> at the POP I don't see a big chance of having any more sizes, as there
> are not a lot of software bits left and adding support in OSs is a pain.
> Also don't hold your breath for 2G, it would need a rewrite of gmap.c.

Well, never say never ... but if you want to keep the current text,
that's fine for me, too.

 Thomas

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