From: Dexuan Cui decui@microsoft.com Sent: Wednesday, May 4, 2022 10:05 AM To: Haiyang Zhang haiyangz@microsoft.com; Wei Liu wei.liu@kernel.org;
... When I initially implemented this driver 10 years ago, I believe there was smaller limit for the fb... But I think this patch is good for the newer MMIO alloc scheme. I hope to see reviews also from @Dexuan Cui @Michael Kelley (LINUX) who are more familiar with the PCI/BAR/MMIO area.
Thanks,
- Haiyang
The patch looks good to me but I suggest we check with the Hyper-V team to figure out how a Gen1 Windows VM supports a higher resolution that needs a VRAM size of more than 64MB. Just in case we miss something..
Thanks, -- Dexuan
Reviewed-by: Dexuan Cui decui@microsoft.com
Saurabh checked this with Hyper-V team, who said there is no Generation 1-specific block for larger VRAM sizes in Windows VM.
When the driver was originally developed, we didn't have the API vmbus_allocate_mmio(), and I guess we just used the PCI device's BAR address for simplicity, and didn't realize the restriction with very high resolutions that require >64 MB VRAM. It looks like the synthetic VMBus framebuffer device doesn't have to use the same MMIO range used by the Hyper-V legacy PCI framebuffer device, so the patch looks good to me.
BTW, please check the hyperv-drm driver as well: drivers/gpu/drm/hyperv/hyperv_drm_drv.c I think we should make the same change there to support 7680x4320 for Gen1 VMs.
Thanks, Dexuan