Messages in this thread | | | Date | Thu, 02 Apr 2015 14:40:04 +1100 | From | Alexey Kardashevskiy <> | Subject | Re: [PATCH kernel v7 04/31] vfio: powerpc/spapr: Use it_page_size |
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On 04/02/2015 01:50 PM, Alex Williamson wrote: > On Thu, 2015-04-02 at 13:30 +1100, Alexey Kardashevskiy wrote: >> 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@ozlabs.ru> >>>> Reviewed-by: David Gibson <david@gibson.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(¤t->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(¤t->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(¤t->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). > > Isn't that a problem then that you're filling the tce with processor > page sizes via get_user_pages_fast(), but incrementing the tce by by > IOMMU page size? For example, if PAGE_SIZE = 4K and IOMMU_PAGE_SIZE != > 4K have we really pinned all of the memory backed by the tce?Where do > you make sure the 4K page is really contiguous for the IOMMU page?
Aaaah. This is just not supported. Instead, after the previous patch ("vfio: powerpc/spapr: Check that TCE page size is equal to it_page_size", which need fixed subject), tce_page_is_contained(page4K, 64K) will return false and the caller - tce_iommu_build() - will return -EPERM.
-- Alexey
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