Re: [RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()
On 2014/11/17 17:22, Paolo Bonzini wrote:
On 17/11/2014 02:34, Chen, Tiejun wrote:
On 2014/11/14 18:06, Paolo Bonzini wrote:
On 14/11/2014 10:31, Tiejun Chen wrote:
In some real scenarios 'start' may not be less than 'end' like
maxphyaddr = 52.
Signed-off-by: Tiejun Chen
---
arch/x86/kvm/mmu.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index bde8ee7..0e98b5e 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -58,6 +58,8 @@
static inline u64 rsvd_bits(int s, int e)
{
+if (unlikely(s > e))
+return 0;
return ((1ULL << (e - s + 1)) - 1) << s;
}
s == e + 1 is supported:
(1ULL << (e - (e + 1) + 1)) - 1) << s ==
(1ULL << (e - (e + 1) + 1)) - 1) << s
= (1ULL << (e - e - 1) + 1)) - 1) << s
= (1ULL << (-1) + 1)) - 1) << s
no,
You're right since I'm seeing "()" wrongly.
Sorry to bother you.
Thanks
Tiejun
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Re: [RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()
On 17/11/2014 02:34, Chen, Tiejun wrote:
> On 2014/11/14 18:06, Paolo Bonzini wrote:
>>
>>
>> On 14/11/2014 10:31, Tiejun Chen wrote:
>>> In some real scenarios 'start' may not be less than 'end' like
>>> maxphyaddr = 52.
>>>
>>> Signed-off-by: Tiejun Chen
>>> ---
>>> arch/x86/kvm/mmu.h | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
>>> index bde8ee7..0e98b5e 100644
>>> --- a/arch/x86/kvm/mmu.h
>>> +++ b/arch/x86/kvm/mmu.h
>>> @@ -58,6 +58,8 @@
>>>
>>> static inline u64 rsvd_bits(int s, int e)
>>> {
>>> +if (unlikely(s > e))
>>> +return 0;
>>> return ((1ULL << (e - s + 1)) - 1) << s;
>>> }
>>>
>>>
>>
>> s == e + 1 is supported:
>>
>> (1ULL << (e - (e + 1) + 1)) - 1) << s ==
>
> (1ULL << (e - (e + 1) + 1)) - 1) << s
> = (1ULL << (e - e - 1) + 1)) - 1) << s
> = (1ULL << (-1) + 1)) - 1) << s
no,
((1ULL << (-1 + 1)) - 1) << s
> = (1ULL << (0) - 1) << s
((1ULL << (0)) - 1) << s
> = (1ULL << (- 1) << s
(1 - 1) << s
0 << s
Paolo
>
> Am I missing something?
>
> Thanks
> Tiejun
>
>> (1ULL << 0) << s ==
>> 0
>>
>> Is there any case where s is even bigger?
>>
>> Paolo
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majord...@vger.kernel.org
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>>
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Re: [RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()
On 2014/11/14 18:06, Paolo Bonzini wrote:
On 14/11/2014 10:31, Tiejun Chen wrote:
In some real scenarios 'start' may not be less than 'end' like
maxphyaddr = 52.
Signed-off-by: Tiejun Chen
---
arch/x86/kvm/mmu.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index bde8ee7..0e98b5e 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -58,6 +58,8 @@
static inline u64 rsvd_bits(int s, int e)
{
+ if (unlikely(s > e))
+ return 0;
return ((1ULL << (e - s + 1)) - 1) << s;
}
s == e + 1 is supported:
(1ULL << (e - (e + 1) + 1)) - 1) << s ==
(1ULL << (e - (e + 1) + 1)) - 1) << s
= (1ULL << (e - e - 1) + 1)) - 1) << s
= (1ULL << (-1) + 1)) - 1) << s
= (1ULL << (0) - 1) << s
= (1ULL << (- 1) << s
Am I missing something?
Thanks
Tiejun
(1ULL << 0) << s ==
0
Is there any case where s is even bigger?
Paolo
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Re: [RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()
On 14/11/2014 10:31, Tiejun Chen wrote:
> In some real scenarios 'start' may not be less than 'end' like
> maxphyaddr = 52.
>
> Signed-off-by: Tiejun Chen
> ---
> arch/x86/kvm/mmu.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index bde8ee7..0e98b5e 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -58,6 +58,8 @@
>
> static inline u64 rsvd_bits(int s, int e)
> {
> + if (unlikely(s > e))
> + return 0;
> return ((1ULL << (e - s + 1)) - 1) << s;
> }
>
>
s == e + 1 is supported:
(1ULL << (e - (e + 1) + 1)) - 1) << s ==
(1ULL << 0) << s ==
0
Is there any case where s is even bigger?
Paolo
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[RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()
In some real scenarios 'start' may not be less than 'end' like
maxphyaddr = 52.
Signed-off-by: Tiejun Chen
---
arch/x86/kvm/mmu.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index bde8ee7..0e98b5e 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -58,6 +58,8 @@
static inline u64 rsvd_bits(int s, int e)
{
+ if (unlikely(s > e))
+ return 0;
return ((1ULL << (e - s + 1)) - 1) << s;
}
--
1.9.1
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