On 14/11/16 11:38, Jan Beulich wrote:
>>>> On 14.11.16 at 12:01, <andrew.coop...@citrix.com> wrote:
>> Luckily, hvm_hypervisor_cpuid_leaf() and vmx_hypervisor_cpuid_leaf() are safe
>> to execute in the context of a PV guest, but HVM-specific feature flags
>> shouldn't be visible to PV guests.
>>
>> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> Reviewed-by: Jan Beulich <jbeul...@suse.com>
> albeit ...
>
>> --- a/xen/arch/x86/traps.c
>> +++ b/xen/arch/x86/traps.c
>> @@ -928,6 +928,11 @@ int cpuid_hypervisor_leaves( uint32_t idx, uint32_t
>> sub_idx,
>> break;
>>
>> case 4:
>> + if ( !has_hvm_container_domain(currd) )
>> + {
>> + *eax = *ebx = *ecx = *edx = 0;
>> + break;
>> + }
>> hvm_hypervisor_cpuid_leaf(sub_idx, eax, ebx, ecx, edx);
>> break;
> ... this being the last leaf, wouldn't we better limit the number of
> leaves (reported in leaf 0) to 3 for PV?
I considered this, but decided not to.
The current max leaf handling is fragile, owing to some dubious control
from the toolstack, and the existence of XEN_CPUID_MAX_NUM_LEAVES in the
public API is absolutely broken.
I am going to need to rework this all anyway, and its not clear whether
we can/should report less than 4 leaves to PV guests.
~Andrew
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