[PATCH v3 01/11] swiotlb-xen: use vmalloc_to_page on vmalloc virt addresses

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

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 (the underlying
issue is not RPi4 specific):
https://marc.info/?l=xen-devel&m=158862573216800

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Tested-by: Corey Minyard <cminyard@xxxxxxxxxx>
Tested-by: Roman Shaposhnik <roman@xxxxxxxxxx>
---
Changes in v3:
- style improvements

Changes in v2:
- update commit message
---
 drivers/xen/swiotlb-xen.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index b6d27762c6f8..5fbadd07819b 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 *page;
 
        if (hwdev && hwdev->coherent_dma_mask)
                dma_mask = hwdev->coherent_dma_mask;
@@ -346,9 +347,14 @@ 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 (is_vmalloc_addr(vaddr))
+               page = vmalloc_to_page(vaddr);
+       else
+               page = 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(page))
                xen_destroy_contiguous_region(phys, order);
 
        xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
-- 
2.17.1