Re: [kvm-unit-tests 2/5] x86: vmx: Named constant: EPT_ADDR_MASK

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2016-03-01 22:16, Peter Feiner wrote:
> On Tue, Mar 1, 2016 at 1:12 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>>
>> On 01/03/2016 20:30, Peter Feiner wrote:
>>> Signed-off-by: Peter Feiner <pfeiner@google.com>
>>> ---
>>>  x86/vmx.c | 6 +++---
>>>  x86/vmx.h | 1 +
>>>  2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/x86/vmx.c b/x86/vmx.c
>>> index 3fa1a73..9811a28 100644
>>> --- a/x86/vmx.c
>>> +++ b/x86/vmx.c
>>> @@ -246,7 +246,7 @@ void install_ept_entry(unsigned long *pml4,
>>>                                       | EPT_RA | EPT_WA | EPT_EA;
>>>               } else
>>>                       pt[offset] &= ~EPT_LARGE_PAGE;
>>> -             pt = phys_to_virt(pt[offset] & 0xffffffffff000ull);
>>> +             pt = phys_to_virt(pt[offset] & EPT_ADDR_MASK);
>>>       }
>>>       offset = ((unsigned long)guest_addr >> ((level-1) *
>>>                       EPT_PGDIR_WIDTH + 12)) & EPT_PGDIR_MASK;
>>> @@ -334,7 +334,7 @@ unsigned long get_ept_pte(unsigned long *pml4,
>>>                       break;
>>>               if (l < 4 && (pte & EPT_LARGE_PAGE))
>>>                       return pte;
>>> -             pt = (unsigned long *)(pte & 0xffffffffff000ull);
>>> +             pt = (unsigned long *)(pte & EPT_ADDR_MASK);
>>>       }
>>>       offset = (guest_addr >> (((l-1) * EPT_PGDIR_WIDTH) + 12))
>>>                       & EPT_PGDIR_MASK;
>>> @@ -378,7 +378,7 @@ int set_ept_pte(unsigned long *pml4, unsigned long guest_addr,
>>>                       break;
>>>               if (!(pt[offset] & (EPT_PRESENT)))
>>>                       return -1;
>>> -             pt = (unsigned long *)(pt[offset] & 0xffffffffff000ull);
>>> +             pt = (unsigned long *)(pt[offset] & EPT_ADDR_MASK);
>>>       }
>>>       offset = (guest_addr >> (((l-1) * EPT_PGDIR_WIDTH) + 12))
>>>                       & EPT_PGDIR_MASK;
>>> diff --git a/x86/vmx.h b/x86/vmx.h
>>> index cae9274..c2a2121 100644
>>> --- a/x86/vmx.h
>>> +++ b/x86/vmx.h
>>> @@ -466,6 +466,7 @@ enum Ctrl1 {
>>>  #define EPT_PAGE_LEVEL               4
>>>  #define EPT_PGDIR_WIDTH              9
>>>  #define EPT_PGDIR_MASK               511
>>> +#define EPT_ADDR_MASK                0xffffffffff000ul
>>
>> This is just PAGE_MASK, defined one line below. :)
>>
>> Paolo
>>
>>>  #define PAGE_MASK            (~(PAGE_SIZE-1))
>>>  #define PAGE_MASK_2M         (~(PAGE_SIZE_2M-1))
>>>
>>>
> 
> It's not precisely the same thing since PAGE_MASK sets the upper
> reserved bits :-)
> 
> I'll send v2.

Consider defining the constant as GENMASK(51, 12) (from linux/bitops.h).

A while back, I re-invented this macro for Jailhouse, and I just
realized that the kernel has the very same thing. It makes such bitmasks
much more readable (and verifiable when looking at specs).

Jan

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