lkml.org 
[lkml]   [2020]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 09/10] xen/arm: introduce phys/dma translations in xen_dma_sync_for_*
    From
    Date
    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

    \
     
     \ /
      Last update: 2020-05-21 10:19    [W:2.626 / U:0.104 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site