| Message ID | 1596478888-23030-12-git-send-email-olekstysh@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | IOREQ feature (+ virtio-mmio) on Arm | expand |
On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > > Without "dma-coherent" property present in virtio-mmio device node, > guest assumes it is non-coherent and making non-cacheable accesses > to the vring when the DMA API is used for vring operations. > But virtio-mmio device which runs at the host size is making cacheable > accesses to vring. This all may result in a loss of coherency between > the guest and host. > > With this patch we can avoid modifying guest at all, otherwise we > need to force VirtIO framework to not use DMA API for vring operations. > > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> This should also be folded in the first patch for libxl > --- > tools/libxl/libxl_arm.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c > index 469a8b0..a68fb14 100644 > --- a/tools/libxl/libxl_arm.c > +++ b/tools/libxl/libxl_arm.c > @@ -726,6 +726,9 @@ static int make_virtio_mmio_node(libxl__gc *gc, void *fdt, > res = fdt_property_interrupts(gc, fdt, &intr, 1); > if (res) return res; > > + res = fdt_property(fdt, "dma-coherent", NULL, 0); > + if (res) return res; > + > res = fdt_end_node(fdt); > if (res) return res; > > -- > 2.7.4 >
On 05.08.20 02:23, Stefano Stabellini wrote: Hi Stefano > On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote: >> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> >> >> Without "dma-coherent" property present in virtio-mmio device node, >> guest assumes it is non-coherent and making non-cacheable accesses >> to the vring when the DMA API is used for vring operations. >> But virtio-mmio device which runs at the host size is making cacheable >> accesses to vring. This all may result in a loss of coherency between >> the guest and host. >> >> With this patch we can avoid modifying guest at all, otherwise we >> need to force VirtIO framework to not use DMA API for vring operations. >> >> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > This should also be folded in the first patch for libxl Agree, will do
diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c index 469a8b0..a68fb14 100644 --- a/tools/libxl/libxl_arm.c +++ b/tools/libxl/libxl_arm.c @@ -726,6 +726,9 @@ static int make_virtio_mmio_node(libxl__gc *gc, void *fdt, res = fdt_property_interrupts(gc, fdt, &intr, 1); if (res) return res; + res = fdt_property(fdt, "dma-coherent", NULL, 0); + if (res) return res; + res = fdt_end_node(fdt); if (res) return res;