Messages in this thread | | | Subject | Re: [PATCH 09/10] xen/arm: introduce phys/dma translations in xen_dma_sync_for_* | From | Julien Grall <> | Date | Thu, 21 May 2020 09:18:35 +0100 |
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Hi,
On 21/05/2020 00:45, Stefano Stabellini wrote: > From: Stefano Stabellini <stefano.stabellini@xilinx.com> > > Add phys_to_dma/dma_to_phys calls to > xen_dma_sync_for_cpu, xen_dma_sync_for_device, and > xen_arch_need_swiotlb. > > In xen_arch_need_swiotlb, take the opportunity to switch to the simpler > pfn_valid check we use everywhere else. > > dma_cache_maint is fixed by the next patch.
Like patch #8, this explains what the code is doing not why this is necessary.
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> > --- > arch/arm/xen/mm.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c > index f2414ea40a79..7639251bcc79 100644 > --- a/arch/arm/xen/mm.c > +++ b/arch/arm/xen/mm.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0-only > #include <linux/cpu.h> > +#include <linux/dma-direct.h> > #include <linux/dma-noncoherent.h> > #include <linux/gfp.h> > #include <linux/highmem.h> > @@ -75,7 +76,7 @@ void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle, > phys_addr_t paddr, size_t size, > enum dma_data_direction dir) > { > - if (pfn_valid(PFN_DOWN(handle))) > + if (pfn_valid(PFN_DOWN(dma_to_phys(dev, handle)))) > arch_sync_dma_for_cpu(paddr, size, dir); > else if (dir != DMA_TO_DEVICE) > dma_cache_maint(handle, size, GNTTAB_CACHE_INVAL); > @@ -85,7 +86,7 @@ void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle, > phys_addr_t paddr, size_t size, > enum dma_data_direction dir) > { > - if (pfn_valid(PFN_DOWN(handle))) > + if (pfn_valid(PFN_DOWN(dma_to_phys(dev, handle)))) > arch_sync_dma_for_device(paddr, size, dir); > else if (dir == DMA_FROM_DEVICE) > dma_cache_maint(handle, size, GNTTAB_CACHE_INVAL); > @@ -97,8 +98,7 @@ bool xen_arch_need_swiotlb(struct device *dev, > phys_addr_t phys, > dma_addr_t dev_addr) > { > - unsigned int xen_pfn = XEN_PFN_DOWN(phys); > - unsigned int bfn = XEN_PFN_DOWN(dev_addr); > + unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr)); > > /* > * The swiotlb buffer should be used if > @@ -115,7 +115,7 @@ bool xen_arch_need_swiotlb(struct device *dev, > * require a bounce buffer because the device doesn't support coherent > * memory and we are not able to flush the cache. > */ > - return (!hypercall_cflush && (xen_pfn != bfn) && > + return (!hypercall_cflush && !pfn_valid(bfn) &&
I believe this change is incorrect. The bfn is a frame based on Xen page granularity (always 4K) while pfn_valid() is expecting a frame based on the Kernel page granularity.
> !dev_is_dma_coherent(dev)); > } > >
Cheers,
-- Julien Grall
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