On 18.07.23 10:26, Vivek Kasireddy wrote:
A user or admin can configure a VMM (Qemu) Guest's memory to be backed by hugetlb pages for various reasons. However, a Guest OS would still allocate (and pin) buffers that are backed by regular 4k sized pages. In order to map these buffers and create dma-bufs for them on the Host, we first need to find the hugetlb pages where the buffer allocations are located and then determine the offsets of individual chunks (within those pages) and use this information to eventually populate a scatterlist.Testcase: default_hugepagesz=2M hugepagesz=2M hugepages=2500 options were passed to the Host kernel and Qemu was launched with these relevant options: qemu-system-x86_64 -m 4096m.... -device virtio-gpu-pci,max_outputs=1,blob=true,xres=1920,yres=1080 -display gtk,gl=on -object memory-backend-memfd,hugetlb=on,id=mem1,size=4096M -machine memory-backend=mem1 Replacing -display gtk,gl=on with -display gtk,gl=off above would exercise the mmap handler. v2: Updated get_sg_table() to manually populate the scatterlist for both huge page and non-huge-page cases. Cc: David Hildenbrand <da...@redhat.com> Cc: Mike Kravetz <mike.krav...@oracle.com> Cc: Hugh Dickins <hu...@google.com> Cc: Peter Xu <pet...@redhat.com> Cc: Jason Gunthorpe <j...@nvidia.com> Cc: Gerd Hoffmann <kra...@redhat.com> Cc: Dongwon Kim <dongwon....@intel.com> Cc: Junxiao Chang <junxiao.ch...@intel.com> Signed-off-by: Vivek Kasireddy <vivek.kasire...@intel.com> --- drivers/dma-buf/udmabuf.c | 84 +++++++++++++++++++++++++++++++++------ 1 file changed, 71 insertions(+), 13 deletions(-)
LGTM, in general. But I really hope Mike can comment. -- Cheers, David / dhildenb
