On Wed, Nov 07, 2018 at 11:04:53AM +0100, Ard Biesheuvel wrote: > On 7 November 2018 at 10:58, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxx> wrote: > > On Wed, Nov 07, 2018 at 09:51:09AM +0000, Marc Zyngier wrote: > >> On 06/11/18 23:49, Russell King - ARM Linux wrote: > >> > On Tue, Nov 06, 2018 at 09:06:56PM +0100, Ard Biesheuvel wrote: > >> >> On 6 November 2018 at 20:08, Russell King - ARM Linux > >> >> <linux@xxxxxxxxxxxxxxx> wrote: > >> >>> On Tue, Nov 06, 2018 at 08:02:58PM +0100, Ard Biesheuvel wrote: > >> >>>> On 6 November 2018 at 12:37, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > >> >>>>> The new memory EFI reservation feature we introduced to allow memory > >> >>>>> reservations to persist across kexec may trigger an unbounded number > >> >>>>> of calls to memblock_reserve(). The memblock subsystem can deal with > >> >>>>> this fine, but not before memblock resizing is enabled, which we can > >> >>>>> only do after paging_init(), when the memory we reallocate the array > >> >>>>> into is actually mapped. > >> >>>>> > >> >>>>> So break out the memreserve table processing into a separate function > >> >>>>> and call if after paging_init() on both arm64 and ARM. > >> >>>>> > >> >>>>> Cc: Russell King <linux@xxxxxxxxxxxxxxx> > >> >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > >> >>>> > >> >>>> Russell, > >> >>>> > >> >>>> If you are ok with this patch, may I have your ack please? I would > >> >>>> like to send it out before the end of the week. > >> >>> > >> >>> You're not going to get a quick answer to this, because it needs me to > >> >>> investigate what the effect of this change actually is by code review. > >> >>> I can't guarantee when I'll get around to that. > >> >>> > >> >> > >> >> Fair enough. > >> >> > >> >> I will drop the ARM hunk for now then, and we'll fix ARM when you have > >> >> more time. > >> > > >> > I don't see how you can do that - you're dropping the processing of > >> > reserved areas out of the efi_config_parse_tables() path, so that > >> > won't happen any more on ARM if you don't apply the ARM hunk. > >> > >> The only reason for the whole persistent region thing is to support > >> GICv3 redistributors memory tables across kexec, for those GIC > >> implementations where LPIs cannot be disabled once they have been > >> enabled. > >> > >> There is no HW platform that combines 32bit cores and GICv3 (not to > >> mention using EFI). The only existing "platform" is KVM/arm64, which > >> doesn't suffer from the above problem (LPIs can be freely disabled in > >> emulation). So the whole persistent region feature serves no purpose on > >> 32bit ARM. > >> > >> The only issue with dropping this hunk is that the memory reservation > >> feature is enabled on 32bit ARM the first place, which can easily be > >> dealt with something along those lines: > > > > So, it was a waste of my time trying to understand what's going on here > > with Ard's patch because it shouldn't be present on 32-bit ARM... Grr. > > > > Not really. I am trying really hard to do my part when it comes to > keeping the maintenance level of the ARM architecture up. That means > that all the improvements and enhancements that are implemented for > EFI on arm64 are enabled on ARM as well, unless there are pressing > reasons not to. > > And even though this persistent reservation feature is only used by > the GICv3 code at the moment, there may be other future uses as well, > so I'd prefer not to special case ARM in this way. Once you've come to some agreement on this, and you've looked at the comment I've made (which leads me to regard your patch as a complete non-starter for 32-bit ARM), I'll continue to look at it. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
