* Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
@ 2019-04-25 8:55 Juergen Gross
0 siblings, 0 replies; 3+ messages in thread
From: Juergen Gross @ 2019-04-25 8:55 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, iommu, xen-devel, Boris Ostrovsky,
Konrad Rzeszutek Wilk, lkml, stable
On 25/04/2019 10:53, Jan Beulich wrote:
>>>> On 23.04.19 at 12:54, <jgross@suse.com> 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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
@ 2019-04-25 9:03 Juergen Gross
0 siblings, 0 replies; 3+ messages in thread
From: Juergen Gross @ 2019-04-25 9:03 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, iommu, xen-devel, Boris Ostrovsky,
Konrad Rzeszutek Wilk, lkml, stable
On 25/04/2019 10:53, Jan Beulich wrote:
>>>> On 23.04.19 at 12:54, <jgross@suse.com> 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.
I know that I modified the condition. Calling
xen_destroy_contiguous_region() for a non-contiguous region is
destructive, so we have to avoid it in any case.
I could be talked into moving both tests into the WARN_ON(), however.
Juergen
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()
2019-04-23 10:54 ` [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region() Juergen Gross
@ 2019-04-25 8:53 ` Jan Beulich
0 siblings, 0 replies; 3+ messages in thread
From: Jan Beulich @ 2019-04-25 8:53 UTC (permalink / raw)
To: Juergen Gross
Cc: Stefano Stabellini, iommu, xen-devel, Boris Ostrovsky,
Konrad Rzeszutek Wilk, linux-kernel, stable
>>> On 23.04.19 at 12:54, <jgross@suse.com> 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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-04-25 9:03 Juergen Gross
2019-04-23 10:54 [PATCH 0/3] xen/swiotlb: fix an issue and improve swiotlb-xen Juergen Gross
2019-04-23 10:54 ` [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region() Juergen Gross
2019-04-25 8:53 ` [Xen-devel] " Jan Beulich
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