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 <[email protected]> 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. > > . >
