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From: Balbir Singh <bsingharora@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Paul Mackerras <paulus@ozlabs.org>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Subject: Re: [RFC][PATCH] Remove duplicate setting of the B field in tlbie
Date: Wed, 14 Sep 2016 16:15:51 +1000	[thread overview]
Message-ID: <4ec47547-2bdf-9d11-b65c-96660aa27bcd@gmail.com> (raw)
In-Reply-To: <8737l3jd1u.fsf@linux.vnet.ibm.com>



On 14/09/16 14:55, Aneesh Kumar K.V wrote:
> Balbir Singh <bsingharora@gmail.com> writes:
> 
>> Remove duplicate setting of the the "B" field when doing a tlbie(l).
>> In compute_tlbie_rb(), the "B" field is set again just before
>> returning the rb value to be used for tlbie(l).
>>
>> Signed-off-by: Balbir Singh <bsingharora@gmail.com>
>> ---
>> Quickly boot tested a VM with these changes in kvm with 64k
>> as the page size for the guest.
>>
>>  arch/powerpc/include/asm/kvm_book3s_64.h | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
>> index 88d17b4..63b6900 100644
>> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
>> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
>> @@ -159,7 +159,6 @@ static inline unsigned long compute_tlbie_rb(unsigned long v, unsigned long r,
>>  	/* This covers 14..54 bits of va*/
>>  	rb = (v & ~0x7fUL) << 16;		/* AVA field */
>>
>> -	rb |= (v >> HPTE_V_SSIZE_SHIFT) << 8;	/*  B field */
>>  	/*
>>  	 * AVA in v had cleared lower 23 bits. We need to derive
>>  	 * that from pteg index
> 
> Can we keep this and remove the other. This is much easier to follow
> than
> 
> 	rb |= (v >> 54) & 0x300;		/* B field */
> 

OK, but I think for 64K page size

                rb &= ~((1ul << mmu_psize_defs[a_psize].shift) - 1);

ends up cleaning up the "B" field. That is why we've had the two "B" field settings.

Let me double check with some coffee.

Balbir Singh.

WARNING: multiple messages have this Message-ID (diff)
From: Balbir Singh <bsingharora@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Paul Mackerras <paulus@ozlabs.org>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Subject: Re: [RFC][PATCH] Remove duplicate setting of the B field in tlbie
Date: Wed, 14 Sep 2016 06:15:51 +0000	[thread overview]
Message-ID: <4ec47547-2bdf-9d11-b65c-96660aa27bcd@gmail.com> (raw)
In-Reply-To: <8737l3jd1u.fsf@linux.vnet.ibm.com>



On 14/09/16 14:55, Aneesh Kumar K.V wrote:
> Balbir Singh <bsingharora@gmail.com> writes:
> 
>> Remove duplicate setting of the the "B" field when doing a tlbie(l).
>> In compute_tlbie_rb(), the "B" field is set again just before
>> returning the rb value to be used for tlbie(l).
>>
>> Signed-off-by: Balbir Singh <bsingharora@gmail.com>
>> ---
>> Quickly boot tested a VM with these changes in kvm with 64k
>> as the page size for the guest.
>>
>>  arch/powerpc/include/asm/kvm_book3s_64.h | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
>> index 88d17b4..63b6900 100644
>> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
>> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
>> @@ -159,7 +159,6 @@ static inline unsigned long compute_tlbie_rb(unsigned long v, unsigned long r,
>>  	/* This covers 14..54 bits of va*/
>>  	rb = (v & ~0x7fUL) << 16;		/* AVA field */
>>
>> -	rb |= (v >> HPTE_V_SSIZE_SHIFT) << 8;	/*  B field */
>>  	/*
>>  	 * AVA in v had cleared lower 23 bits. We need to derive
>>  	 * that from pteg index
> 
> Can we keep this and remove the other. This is much easier to follow
> than
> 
> 	rb |= (v >> 54) & 0x300;		/* B field */
> 

OK, but I think for 64K page size

                rb &= ~((1ul << mmu_psize_defs[a_psize].shift) - 1);

ends up cleaning up the "B" field. That is why we've had the two "B" field settings.

Let me double check with some coffee.

Balbir Singh.

  reply	other threads:[~2016-09-14  6:15 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-13  7:45 [RFC][PATCH] Remove duplicate setting of the B field in tlbie Balbir Singh
2016-09-13  7:45 ` Balbir Singh
2016-09-14  4:55 ` Aneesh Kumar K.V
2016-09-14  4:55   ` Aneesh Kumar K.V
2016-09-14  6:15   ` Balbir Singh [this message]
2016-09-14  6:15     ` Balbir Singh

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