linux-kernel - RE: [PATCH v4] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.

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Message-ID: <CY4PR21MB06293C21EC5338C98080F6AED7580@CY4PR21MB0629.namprd21.prod.outlook.com>
Date:   Mon, 9 Dec 2019 16:32:56 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Wei Hu <weh@...rosoft.com>,
        "b.zolnierkie@...sung.com" <b.zolnierkie@...sung.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>, "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "mchehab+samsung@...nel.org" <mchehab+samsung@...nel.org>,
        "sam@...nborg.org" <sam@...nborg.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "info@...ux.net" <info@...ux.net>, "arnd@...db.de" <arnd@...db.de>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>
CC:     kbuild test robot <lkp@...el.com>
Subject: RE: [PATCH v4] video: hyperv: hyperv_fb: Use physical memory for fb
 on HyperV Gen 1 VMs.

From: Wei Hu <weh@...rosoft.com> 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@...el.com>
> Signed-off-by: Wei Hu <weh@...rosoft.com>
> ---
>     v2: Incorporated review comments form hch@....de, 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@...rosoft.com>