Re: [Qemu-devel] [PATCH 12/13] hw/rdma: Bugfix: Support non-aligned buffers

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

On 07/16/2018 10:40 AM, Yuval Shaia wrote:
> RDMA applications can provide non-aligned buffers to be registered. In
> such case the DMA address passed by driver is pointing to the beginning
> of the physical address of the mapped page so we can't distinguish
> between two addresses from the same page.
>
> Fix it by keeping the offset of the virtual address in mr->virt.
>
> Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
> ---
>   hw/rdma/rdma_rm.c        | 2 ++
>   hw/rdma/vmw/pvrdma_cmd.c | 1 +
>   2 files changed, 3 insertions(+)
>
> diff --git a/hw/rdma/rdma_rm.c b/hw/rdma/rdma_rm.c
> index 859c900003..8d59a42cd1 100644
> --- a/hw/rdma/rdma_rm.c
> +++ b/hw/rdma/rdma_rm.c
> @@ -166,6 +166,7 @@ int rdma_rm_alloc_mr(RdmaDeviceResources *dev_res, uint32_t pd_handle,
>           mr->virt = host_virt;
>           mr->start = guest_start;
>           mr->length = guest_length;
> +        mr->virt += (mr->start & (TARGET_PAGE_SIZE - 1));
>   
>           ret = rdma_backend_create_mr(&mr->backend_mr, &pd->backend_pd, mr->virt,
>                                        mr->length, access_flags);
> @@ -203,6 +204,7 @@ void rdma_rm_dealloc_mr(RdmaDeviceResources *dev_res, uint32_t mr_handle)
>           rdma_backend_destroy_mr(&mr->backend_mr);
>           pr_dbg("start=0x%" PRIx64 "\n", mr->start);
>           if (mr->start) {
> +            mr->virt -= (mr->start & (TARGET_PAGE_SIZE - 1));
>               munmap(mr->virt, mr->length);
>           }
>           res_tbl_dealloc(&dev_res->mr_tbl, mr_handle);
> diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
> index bb898265a3..4ff242e793 100644
> --- a/hw/rdma/vmw/pvrdma_cmd.c
> +++ b/hw/rdma/vmw/pvrdma_cmd.c
> @@ -59,6 +59,7 @@ static void *pvrdma_map_to_pdir(PCIDevice *pdev, uint64_t pdir_dma,
>       }
>   
>       host_virt = mremap(curr_page, 0, length, MREMAP_MAYMOVE);
> +    pr_dbg("mremap %p -> %p\n", curr_page, host_virt);
>       if (host_virt == MAP_FAILED) {
>           host_virt = NULL;
>           error_report("PVRDMA: Failed to remap memory for host_virt");

Nice catch!

Reviewed-by: Marcel Apfelbaum<marcel.apfelbaum@gmail.com>

Thanks,
Marcel