From: Wei Hu <weh@xxxxxxxxxxxxx> Sent: Sunday, December 8, 2019 11:58 PM > > On Hyper-V, Generation 1 VMs can directly use VM's physical memory for > their framebuffers. This can improve the efficiency of framebuffer and > overall performence for VM. The physical memory assigned to framebuffer > must be contiguous. We use CMA allocator to get contiguouse physicial > memory when the framebuffer size is greater than 4MB. For size under > 4MB, we use alloc_pages to achieve this. > > To enable framebuffer memory allocation from CMA, supply a kernel > parameter to give enough space to CMA allocator at boot time. For > example: > cma=130m > This gives 130MB memory to CAM allocator that can be allocated to > framebuffer. If this fails, we fall back to the old way of using > mmio for framebuffer. > > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > Signed-off-by: Wei Hu <weh@xxxxxxxxxxxxx> > --- > v2: Incorporated review comments form hch@xxxxxx, Michael Kelley and > Dexuan Cui > - Use dma_alloc_coherent to allocate large contiguous memory > - Use phys_addr_t for physical addresses > - Corrected a few spelling errors and minor cleanups > - Also tested on 32 bit Ubuntu guest > v3: Fixed a build issue reported by kbuild test robot and incorported > some review comments from Michael Kelley > - Add CMA check to avoid link failure > - Fixed small memory leak introduced by alloc_apertures > - Cleaned up so code > v4: Removed request_pages variable as it is no longer needed > > drivers/video/fbdev/Kconfig | 1 + > drivers/video/fbdev/hyperv_fb.c | 182 +++++++++++++++++++++++++------- > 2 files changed, 144 insertions(+), 39 deletions(-) > Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
