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Date: Mon, 27 Feb 2017 18:24:44 +0800 From: Yisheng Xie <xieyisheng1@...wei.com> To: Mark Rutland <mark.rutland@....com> CC: Ard Biesheuvel <ard.biesheuvel@...aro.org>, Leif Lindholm <leif.lindholm@...aro.org>, Catalin Marinas <catalin.marinas@....com>, "Will Deacon" <will.deacon@....com>, Kefeng Wang <wangkefeng.wang@...wei.com>, Jisheng Zhang <jszhang@...vell.com>, Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>, Laura Abbott <labbott@...hat.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Hanjun Guo <guohanjun@...wei.com>, <dongbo4@...wei.com> Subject: Re: [PATCH RFC] arm64/mm: handle memmap kernel option hi Mark, Thanks for comment On 2017/2/27 16:48, Mark Rutland wrote: > Hi, > > On Mon, Feb 27, 2017 at 11:48:50AM +0800, Yisheng Xie wrote: >> On 2017/2/26 18:46, Ard Biesheuvel wrote: >>> On 25 February 2017 at 06:47, Yisheng Xie <xieyisheng1@...wei.com> wrote: > >>>> To make user reserve memory for some specific use more convenient, >>>> this patch implement the following memmap variants: >>>> - memmap=nn[KMG]$ss[KMG]: mark specified memory as reserved; >>>> - memmap=nn[KMG]@ss[KMG]: force usage of a specific region of memory; > >>> Could you explain which problem you are solving here? ACPI implies >>> UEFI on arm64, and so these reservations could be made by a boot >>> component instead, if it requires a fixed memory reservation. If this >>> is a reservation for, e.g., OP-TEE, we should not rely on the command >>> line to communicate this information. >>> >> We just want to reserve some memory for a driver and I just not so familiar >> with how to reserve memory with UEFI. So doubt about whether it is suitable >> to reserve memory with cmdline like "memmap=xxx", which had appeared in x86 >> for a long time. > > Could you please explain for what purpose this is necessary? > > Does the driver need a specific region of memory? Or just some contiguous > region? Or something else? > Yes, we want to use a specific region of memory. > For the former, this is not an appropriate solution; firmware must absolutely > mark the memory as reserved for a particular purpose. > I see, so just forget about this patch. sorry for disturbing. Thanks again for your explain. Yisheng Xie > If you just need contiguous physical memory, I believe it would be better to > use CMA, and request CMA reserve a larger area if necessary. > > Thanks, > Mark. > > . >
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