[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] vfio: convert to 128 bit arithmetic calculation
From: |
Alex Williamson |
Subject: |
Re: [Qemu-devel] [PATCH] vfio: convert to 128 bit arithmetic calculations when adding mem regions |
Date: |
Wed, 23 Mar 2016 17:00:16 -0600 |
On Wed, 23 Mar 2016 16:57:35 -0400
Bandan Das <address@hidden> wrote:
> vfio_listener_region_add for a iommu mr results in
> an overflow assert since vt-d memory region is initialized
> with UINT64_MAX. Convert calculations to 128 bit arithmetic
> for such regions and let int128_get64 assert for non iommu
> regions only.
>
> Suggested-by: Alex Williamson <address@hidden>
> Signed-off-by: Bandan Das <address@hidden>
> ---
> This is v2 of http://patchwork.ozlabs.org/patch/600364/
> hw/vfio/common.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index fb588d8..9489ff3 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -323,7 +323,7 @@ static void vfio_listener_region_add(MemoryListener
> *listener,
> {
> VFIOContainer *container = container_of(listener, VFIOContainer,
> listener);
> hwaddr iova, end;
> - Int128 llend;
> + Int128 llend, endaddr;
> void *vaddr;
> int ret;
>
> @@ -349,14 +349,15 @@ static void vfio_listener_region_add(MemoryListener
> *listener,
> if (int128_ge(int128_make64(iova), llend)) {
> return;
> }
> - end = int128_get64(llend);
> + endaddr = int128_sub(llend, int128_one());
I like where this is headed, but there's maybe a little polish left.
endaddr here can never be greater than UINT64_MAX, so why don't we make
it a hwaddr and wrap the whole right side of the equation in an
int128_get64(). Then the (end - 1) changes below don't need the
extra int128 ops.
>
> - if ((iova < container->min_iova) || ((end - 1) > container->max_iova)) {
> - error_report("vfio: IOMMU container %p can't map guest IOVA region"
> - " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
> - container, iova, end - 1);
> - ret = -EFAULT;
> - goto fail;
> + if ((iova < container->min_iova) || (int128_get64(endaddr) >
> + container->max_iova)) {
> + error_report("vfio: IOMMU container %p can't map guest IOVA
> region"
> + " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
> + container, iova, int128_get64(endaddr));
> + ret = -EFAULT;
> + goto fail;
Bogus whitespace changes
> }
>
> memory_region_ref(section->mr);
> @@ -364,7 +365,7 @@ static void vfio_listener_region_add(MemoryListener
> *listener,
> if (memory_region_is_iommu(section->mr)) {
> VFIOGuestIOMMU *giommu;
>
> - trace_vfio_listener_region_add_iommu(iova, end - 1);
> + trace_vfio_listener_region_add_iommu(iova, int128_get64(endaddr));
> /*
> * FIXME: We should do some checking to see if the
> * capabilities of the host VFIO IOMMU are adequate to model
> @@ -389,6 +390,8 @@ static void vfio_listener_region_add(MemoryListener
> *listener,
> return;
> }
>
> + end = int128_get64(llend);
> +
> /* Here we assume that memory_region_is_ram(section->mr)==true */
>
> vaddr = memory_region_get_ram_ptr(section->mr) +
For this last chunk I'd do something like this:
+ llsize = int128_sub(llend, int128_make64(iova));
- ret = vfio_dma_map(container, iova, end - iova, vaddr, section->readonly);
+ ret = vfio_dma_map(container, iova,
+ int128_get64(llsize), vaddr, section->readonly);
if (ret) {
error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
"0x%"HWADDR_PRIx", %p) = %d (%m)",
- container, iova, end - iova, vaddr, ret);
+ container, iova, int128_get64(llsize), vaddr, ret);
goto fail;
}
This maintains the 128bit math until exactly the point where it will
fall apart when vfio_dma_map can't pass an int128 to the vfio API.
Thanks,
Alex