From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen_alloc_coherent_pages might return pages for which virt_to_phys and
virt_to_page don't work, e.g. ioremap'ed pages.

So in xen_swiotlb_free_coherent we can't assume that virt_to_page works.
Instead add a is_vmalloc_addr check and use vmalloc_to_page on vmalloc
virt addresses.

This patch fixes the following crash at boot on RPi4:
https://marc.info/?l=xen-devel&m=158862573216800

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Tested-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Roman Shaposhnik <roman@zededa.com>
---
Changes in v2:
- update commit message
---
 drivers/xen/swiotlb-xen.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index b6d27762c6f8..a42129cba36e 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -335,6 +335,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
 	int order = get_order(size);
 	phys_addr_t phys;
 	u64 dma_mask = DMA_BIT_MASK(32);
+	struct page *pg;
 
 	if (hwdev && hwdev->coherent_dma_mask)
 		dma_mask = hwdev->coherent_dma_mask;
@@ -346,9 +347,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
 	/* Convert the size to actually allocated. */
 	size = 1UL << (order + XEN_PAGE_SHIFT);
 
+	pg = is_vmalloc_addr(vaddr) ? vmalloc_to_page(vaddr) :
+				      virt_to_page(vaddr);
 	if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
 		     range_straddles_page_boundary(phys, size)) &&
-	    TestClearPageXenRemapped(virt_to_page(vaddr)))
+	    TestClearPageXenRemapped(pg))
 		xen_destroy_contiguous_region(phys, order);
 
 	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
-- 
2.17.1

Well, this isn't just RPi4, but basically any ARM or ARM64 system
with non-coherent DMA (which is most of them).

> +	struct page *pg;

Please spell out page.

>  
>  	if (hwdev && hwdev->coherent_dma_mask)
>  		dma_mask = hwdev->coherent_dma_mask;
> @@ -346,9 +347,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>  	/* Convert the size to actually allocated. */
>  	size = 1UL << (order + XEN_PAGE_SHIFT);
>  
> +	pg = is_vmalloc_addr(vaddr) ? vmalloc_to_page(vaddr) :
> +				      virt_to_page(vaddr);

Please use plain old if/else to make this more readable.

Hi Christoph,

Thanks you for the review.


On Mon, 8 Jun 2020, Christoph Hellwig wrote:
> Well, this isn't just RPi4, but basically any ARM or ARM64 system
> with non-coherent DMA (which is most of them).

Well... yes :-)


> > +	struct page *pg;
> 
> Please spell out page.

OK


> >  
> >  	if (hwdev && hwdev->coherent_dma_mask)
> >  		dma_mask = hwdev->coherent_dma_mask;
> > @@ -346,9 +347,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
> >  	/* Convert the size to actually allocated. */
> >  	size = 1UL << (order + XEN_PAGE_SHIFT);
> >  
> > +	pg = is_vmalloc_addr(vaddr) ? vmalloc_to_page(vaddr) :
> > +				      virt_to_page(vaddr);
> 
> Please use plain old if/else to make this more readable.

Sure