Re: [PATCH] x86/vtd: fix EPT page table sharing check

[Jan Beulich <jbeulich@xxxxxxxx>]

On 17.04.2020 13:16, Roger Pau Monné wrote:
> On Fri, Apr 17, 2020 at 12:57:16PM +0200, Jan Beulich wrote:
>> On 17.04.2020 12:26, Roger Pau Monne wrote:
>>> --- a/xen/drivers/passthrough/vtd/iommu.c
>>> +++ b/xen/drivers/passthrough/vtd/iommu.c
>>> @@ -1914,8 +1914,10 @@ static int __init vtd_ept_page_compatible(struct 
>>> vtd_iommu *iommu)
>>>      if ( rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, ept_cap) != 0 ) 
>>>          return 0;
>>>  
>>> -    return (ept_has_2mb(ept_cap) && opt_hap_2mb) == cap_sps_2mb(vtd_cap) &&
>>> -           (ept_has_1gb(ept_cap) && opt_hap_1gb) == cap_sps_1gb(vtd_cap);
>>> +    return ((ept_has_2mb(ept_cap) && opt_hap_2mb) ? cap_sps_2mb(vtd_cap)
>>> +                                                  : true) &&
>>> +           ((ept_has_1gb(ept_cap) && opt_hap_1gb) ? cap_sps_1gb(vtd_cap)
>>> +                                                  : true);
>>
>> I have to admit that I always find it odd to have "true" or "false"
>> as the 2nd or 3rd operand of a ternary. How about simply changing
>> == to <= in the original expression?
> 
> I find it weird to use <= to compare booleans, but I can change it.

In the end Kevin will have to judge what variant to use.

> Let me post a new version with the adjustments to the commit message
> and this requested change.

Thanks.

Jan