linux-kernel - Re: [PATCH kernel v7 04/31] vfio: powerpc/spapr: Use it_page

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Date:	Thu, 02 Apr 2015 13:30:47 +1100
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	linuxppc-dev@...ts.ozlabs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v7 04/31] vfio: powerpc/spapr: Use it_page_size

On 04/02/2015 08:48 AM, Alex Williamson wrote:
> On Sat, 2015-03-28 at 01:54 +1100, Alexey Kardashevskiy wrote:
>> This makes use of the it_page_size from the iommu_table struct
>> as page size can differ.
>>
>> This replaces missing IOMMU_PAGE_SHIFT macro in commented debug code
>> as recently introduced IOMMU_PAGE_XXX macros do not include
>> IOMMU_PAGE_SHIFT.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
>> Reviewed-by: David Gibson <david@...son.dropbear.id.au>
>> ---
>>   drivers/vfio/vfio_iommu_spapr_tce.c | 26 +++++++++++++-------------
>>   1 file changed, 13 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
>> index f835e63..8bbee22 100644
>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>> @@ -91,7 +91,7 @@ static int tce_iommu_enable(struct tce_container *container)
>>   	 * enforcing the limit based on the max that the guest can map.
>>   	 */
>>   	down_write(&current->mm->mmap_sem);
>> -	npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>> +	npages = (tbl->it_size << tbl->it_page_shift) >> PAGE_SHIFT;
>>   	locked = current->mm->locked_vm + npages;
>>   	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>>   	if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
>> @@ -120,7 +120,7 @@ static void tce_iommu_disable(struct tce_container *container)
>>
>>   	down_write(&current->mm->mmap_sem);
>>   	current->mm->locked_vm -= (container->tbl->it_size <<
>> -			IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>> +			container->tbl->it_page_shift) >> PAGE_SHIFT;
>>   	up_write(&current->mm->mmap_sem);
>>   }
>>
>> @@ -222,7 +222,7 @@ static long tce_iommu_build(struct tce_container *container,
>>   					tce, ret);
>>   			break;
>>   		}
>> -		tce += IOMMU_PAGE_SIZE_4K;
>> +		tce += IOMMU_PAGE_SIZE(tbl);
>
>
> Is PAGE_SIZE ever smaller than IOMMU_PAGE_SIZE(tbl)?  IOW, can the page
> we got from get_user_pages_fast() ever not completely fill the tce
> entry?


Yes. IOMMU_PAGE_SIZE is 4K/64K/16M (16M is with huge pages enabled in QEMU 
with -mempath), PAGE_SIZE is 4K/64K (normally 64K).


> (Have I asked this before?  Sorry if so)


:)



-- 
Alexey
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