Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
>>> On 23.04.19 at 12:54, wrote:
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t
> size, void *vaddr,
> /* Convert the size to actually allocated. */
> size = 1UL << (order + XEN_PAGE_SHIFT);
>
> - if (((dev_addr + size - 1 <= dma_mask)) ||
> - range_straddles_page_boundary(phys, size))
> + if ((dev_addr + size - 1 <= dma_mask) &&
> + !WARN_ON(range_straddles_page_boundary(phys, size)))
> xen_destroy_contiguous_region(phys, order);
On the allocation side we have
if (((dev_addr + size - 1 <= dma_mask)) &&
!range_straddles_page_boundary(phys, size))
*dma_handle = dev_addr;
else {
if (xen_create_contiguous_region(phys, order,
fls64(dma_mask), dma_handle)
!= 0) {
xen_free_coherent_pages(hwdev, size, ret,
(dma_addr_t)phys, attrs);
return NULL;
}
}
which is (as far as the function call is concerned)
if ((dev_addr + size - 1 > dma_mask) ||
range_straddles_page_boundary(phys, size))
xen_create_contiguous_region(...);
So I don't think your transformation is correct. Even worse, both
parts of the condition in xen_swiotlb_free_coherent() act on an
address that is the _result_ of the prior
xen_create_contiguous_region(), i.e. the address should always
match _both_ criteria anyway. Whereas what you really want is
undo the xen_create_contiguous_region() only when it actually
was called. Otherwise you also shatter contiguous allocations
that were contiguous already for other reasons (perhaps just
luck).
Jan
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Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
On 25/04/2019 10:53, Jan Beulich wrote:
On 23.04.19 at 12:54, wrote:
>> --- a/drivers/xen/swiotlb-xen.c
>> +++ b/drivers/xen/swiotlb-xen.c
>> @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t
>> size, void *vaddr,
>> /* Convert the size to actually allocated. */
>> size = 1UL << (order + XEN_PAGE_SHIFT);
>>
>> -if (((dev_addr + size - 1 <= dma_mask)) ||
>> -range_straddles_page_boundary(phys, size))
>> +if ((dev_addr + size - 1 <= dma_mask) &&
>> +!WARN_ON(range_straddles_page_boundary(phys, size)))
>> xen_destroy_contiguous_region(phys, order);
>
> On the allocation side we have
>
> if (((dev_addr + size - 1 <= dma_mask)) &&
> !range_straddles_page_boundary(phys, size))
> *dma_handle = dev_addr;
> else {
> if (xen_create_contiguous_region(phys, order,
>fls64(dma_mask), dma_handle)
> != 0) {
> xen_free_coherent_pages(hwdev, size, ret,
> (dma_addr_t)phys, attrs);
> return NULL;
> }
> }
>
> which is (as far as the function call is concerned)
>
> if ((dev_addr + size - 1 > dma_mask) ||
> range_straddles_page_boundary(phys, size))
> xen_create_contiguous_region(...);
>
> So I don't think your transformation is correct. Even worse, both
> parts of the condition in xen_swiotlb_free_coherent() act on an
> address that is the _result_ of the prior
> xen_create_contiguous_region(), i.e. the address should always
> match _both_ criteria anyway. Whereas what you really want is
> undo the xen_create_contiguous_region() only when it actually
> was called. Otherwise you also shatter contiguous allocations
> that were contiguous already for other reasons (perhaps just
> luck).
Yes, that is what patch 3 does.
Juergen
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Re: [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
On 4/23/19 6:54 AM, Juergen Gross wrote: > The condition in xen_swiotlb_free_coherent() for deciding whether to > call xen_destroy_contiguous_region() is wrong: in case the region to > be freed is not contiguous calling xen_destroy_contiguous_region() is > the wrong thing to do: it would result in inconsistent mappings of > multiple PFNs to the same MFN. This will lead to various strange > crashes or data corruption. > > Instead of calling xen_destroy_contiguous_region() in that case a > warning should be issued as that situation should never occur. > > Cc: sta...@vger.kernel.org > Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
[PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
The condition in xen_swiotlb_free_coherent() for deciding whether to call xen_destroy_contiguous_region() is wrong: in case the region to be freed is not contiguous calling xen_destroy_contiguous_region() is the wrong thing to do: it would result in inconsistent mappings of multiple PFNs to the same MFN. This will lead to various strange crashes or data corruption. Instead of calling xen_destroy_contiguous_region() in that case a warning should be issued as that situation should never occur. Cc: sta...@vger.kernel.org Signed-off-by: Juergen Gross --- drivers/xen/swiotlb-xen.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 877baf2a94f4..42a3924e6d91 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT); - if (((dev_addr + size - 1 <= dma_mask)) || - range_straddles_page_boundary(phys, size)) + if ((dev_addr + size - 1 <= dma_mask) && + !WARN_ON(range_straddles_page_boundary(phys, size))) xen_destroy_contiguous_region(phys, order); xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs); -- 2.16.4 ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
