Re: [PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses
From: Roman Skakun
Date: Thu Jul 15 2021 - 03:31:51 EST
Hi, Stefano!
> We have the same thing in xen_swiotlb_free_coherent. Can we find a way
> to call cpu_addr_to_page() from xen_swiotlb_free_coherent?
> Maybe we can make cpu_addr_to_page non-static?
Yes, right, If we want to reuse this helper instead of the same code
block in xen_swiotlb_free_coherent() need to make cpu_addr_to_page() as
global and add a new declaration for this helper in include/linux/dma-map-ops.h.
What do you think?
Cheers!
ср, 14 июл. 2021 г. в 04:23, Stefano Stabellini <sstabellini@xxxxxxxxxx>:
>
> On Tue, 22 Jun 2021, Roman Skakun wrote:
> > This commit is dedicated to fix incorrect conversion from
> > cpu_addr to page address in cases when we get virtual
> > address which allocated in the vmalloc range.
> > As the result, virt_to_page() cannot convert this address
> > properly and return incorrect page address.
> >
> > Need to detect such cases and obtains the page address using
> > vmalloc_to_page() instead.
> >
> > Signed-off-by: Roman Skakun <roman_skakun@xxxxxxxx>
> > Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
> > ---
> > Hey!
> > Thanks for suggestions, Christoph!
> > I updated the patch according to your advice.
> > But, I'm so surprised because nobody catches this problem
> > in the common code before. It looks a bit strange as for me.
> >
> >
> > kernel/dma/ops_helpers.c | 12 ++++++++++--
> > 1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
> > index 910ae69cae77..782728d8a393 100644
> > --- a/kernel/dma/ops_helpers.c
> > +++ b/kernel/dma/ops_helpers.c
> > @@ -5,6 +5,14 @@
> > */
> > #include <linux/dma-map-ops.h>
> >
> > +static struct page *cpu_addr_to_page(void *cpu_addr)
> > +{
> > + if (is_vmalloc_addr(cpu_addr))
> > + return vmalloc_to_page(cpu_addr);
> > + else
> > + return virt_to_page(cpu_addr);
> > +}
>
> We have the same thing in xen_swiotlb_free_coherent. Can we find a way
> to call cpu_addr_to_page() from xen_swiotlb_free_coherent? Maybe we can
> make cpu_addr_to_page non-static? No problem if it is too much trouble.
>
>
> > /*
> > * Create scatter-list for the already allocated DMA buffer.
> > */
> > @@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
> > void *cpu_addr, dma_addr_t dma_addr, size_t size,
> > unsigned long attrs)
> > {
> > - struct page *page = virt_to_page(cpu_addr);
> > + struct page *page = cpu_addr_to_page(cpu_addr);
> > int ret;
> >
> > ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> > @@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> > return -ENXIO;
> >
> > return remap_pfn_range(vma, vma->vm_start,
> > - page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
> > + page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
> > user_count << PAGE_SHIFT, vma->vm_page_prot);
> > #else
> > return -ENXIO;
> > --
> > 2.25.1
> >
--
Best Regards, Roman.