Re: [Xen-devel] [PATCH v7 24/32] xen/x86: allow disabling all emulated devices inside of Xen

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.10.15 at 17:20, <roger.pau@xxxxxxxxxx> wrote:
> El 19/10/15 a les 16.23, Jan Beulich ha escrit:
>>>>> On 02.10.15 at 17:48, <roger.pau@xxxxxxxxxx> wrote:
>>> Only allow enabling or disabling all the emulated devices inside of Xen,
>>> right now Xen doesn't support enabling specific emulated devices only.
>>>
>>> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
>>> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> ---
>>> Changes since v5:
>>>  - Add Andrew Cooper Reviewed-by.
>>> ---
>>>  xen/arch/x86/domain.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
>>> index 79182a4..a3b1c9b 100644
>>> --- a/xen/arch/x86/domain.c
>>> +++ b/xen/arch/x86/domain.c
>>> @@ -526,7 +526,8 @@ int arch_domain_create(struct domain *d, unsigned int 
>>> domcr_flags,
>>>                 d->domain_id, config->emulation_flags);
>>>          return -EINVAL;
>>>      }
>>> -    if ( (is_hvm_domain(d) && config->emulation_flags != XEN_X86_EMU_ALL) 
>>> ||
>>> +    if ( (is_hvm_domain(d) && config->emulation_flags != XEN_X86_EMU_ALL &&
>>> +         config->emulation_flags != 0) ||
>>>           (is_pv_domain(d) && config->emulation_flags != 0) )
>> 
>> Would there be any bad in simplifying this to
>> 
>>     if ( config->emulation_flags != 0 && (!is_hvm_domain(d) || 
>> config->emulation_flags != XEN_X86_EMU_ALL) )
>> 
>> (i.e. allowing flags to be zero for all kinds)?
> 
> IMHO I find this harder to read, but I guess that's a question of taste,
> I've replaced it with your suggestion.

I have a hard time seeing how a 3 component logical expression
can be harder to read than a 5 component one.

Jan

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