On 27 February 2017 at 10:24, Yisheng Xie <[email protected]> wrote: > 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. >>
Indeed. The reason is that UEFI performs memory allocations itself, and so putting memmap=xxx on the command line does not prevent the region from being occupied when the kernel boots. > I see, so just forget about this patch. sorry for disturbing. > No worries. Thanks for the patch, Ard.
