On 02/26/2014 05:49 PM, Rob Herring wrote: > On Wed, Feb 26, 2014 at 1:55 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >> On Wednesday 26 February 2014 10:34:54 Christoffer Dall wrote: >>> ARM VM System Specification >>> =========================== >>> >>> Goal >>> ---- >>> The goal of this spec is to allow suitably-built OS images to run on >>> all ARM virtualization solutions, such as KVM or Xen. >>> >>> Recommendations in this spec are valid for aarch32 and aarch64 alike, and >>> they aim to be hypervisor agnostic. >>> >>> Note that simply adhering to the SBSA [2] is not a valid approach, >>> for example because the SBSA mandates EL2, which will not be available >>> for VMs. Further, the SBSA mandates peripherals like the pl011, which >>> may be controversial for some ARM VM implementations to support. >>> This spec also covers the aarch32 execution mode, not covered in the >>> SBSA. >> >> I would prefer if we can stay as close as possible to SBSA for individual >> hardware components, and only stray from it when there is a strong reason. >> pl011-subset doesn't sound like a significant problem to implement, >> especially as SBSA makes the DMA part of that optional. Can you >> elaborate on what hypervisor would have a problem with that? > > The SBSA only spec's a very minimal pl011 subset which is only > suitable for early serial output. Not only is there no DMA, but there > are no interrupts and maybe no input. I think it also assumes the uart > is enabled and configured already by firmware. It is all somewhat > pointless because the location is still not known or discoverable by > early code. Just mandating a real pl011 would have been better, but I > guess uart IP is value add for some. There is a downside to the pl011 > which is the tty name is different from x86 uarts which gets exposed > to users and things like libvirt. Can you just use /dev/console? That's what I use in my init scripts for portability from PL011 to DCC. Christopher -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
