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? For the former, this is not an appropriate solution; firmware must absolutely mark the memory as reserved for a particular purpose. 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.
