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Re: [Qemu-devel] [PATCH] vfio: convert to 128 bit arithmetic calculation
From: |
Bandan Das |
Subject: |
Re: [Qemu-devel] [PATCH] vfio: convert to 128 bit arithmetic calculations when adding mem regions |
Date: |
Wed, 23 Mar 2016 20:20:19 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Alex Williamson <address@hidden> writes:
...
>>
>> 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.
Sounds good.
>>
>> - 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
Oops, sorry!
>> }
>>
>> 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.
Yep, sounds good. v2 coming up shortly.
> Thanks,
>
> Alex