ARM64: Disabling warnings about deprecated armv8 instructions

[Jisheng Zhang]

On Sun, 22 Jan 2017 00:58:48 -0800 Michael Zoran wrote:

> On Sun, 2017-01-22 at 09:52 +0100, Alexander Stein wrote:
> > Hi Michael,
> > 
> > On Sunday, January 22, 2017, 12:07:04 AM CET Michael Zoran wrote:  
> > > I'm not sure if this if the correct place to be asking this.   The
> > > RPI
> > > 3 running ARM64 is slowly reaching the point of being about to
> > > seriously run a 32 bit vender OS like Raspbian.  When running
> > > Raspbian,
> > > I'm seeing a very large number(thousands) of kernel log messages
> > > about
> > > deprecated instructions especially setend and barrier instuctions.
> > > This can be very annoying and is completely filling the kernel log.
> > > 
> > > I'm considering submitting a patch to add a Kconfig option to
> > > disable
> > > these warnings with the default being to keep the warnings
> > > enabled.  I
> > > was wondering if such a patch could be seriously considered.  
> > 
> > Could you please provide an example of those warning an what is
> > trigging 
> > those?
> > 
> > Thanks and best regards,
> > Alexander  
> 
> Sure, here is a snipped from dmesg.  I think this is happening because
> the entire Raspbian OS is compiled with a custom gcc compiler that is
> targeting arm6+VFP.

IMHO, this is the root cause. I didn't see below warnings from dmesg with
armhf debian and ubuntu If the underlying HW is armv8 compatible, it
doesn't make sense to target the compiler to armv6

Thanks

> 
> I can double check, but I think the instructions are being emulated in 
> hardware so they are just filling the log and slowing things down.
> 
> [10685.558480] cp15barrier_handler: 197896 callbacks suppressed
> [10685.558487] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf707fe9c
> [10685.558504] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7015944
> [10685.558511] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7012494
> [10685.558518] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf70159b4
> [10685.558527] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7011478
> [10685.558533] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf70114e8
> [10685.558540] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7015944
> [10685.558547] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7012494
> [10685.558553] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf70159b4
> [10685.558560] "Xorg" (656) uses deprecated CP15 Barrier instruction at
> 0xf7011478
> [10685.559179] compat_setend_handler: 1078 callbacks suppressed
> [10685.559188] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a66f4
> [10685.559196] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a6bd8
> [10685.559209] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a66f4
> [10685.559216] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a6bd8
> [10685.559231] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a66f4
> [10685.559237] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a6bd8
> [10685.559246] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a66f4
> [10685.559253] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a6bd8
> [10685.559269] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a66f4
> [10685.559276] "systemd-journal" (138) uses deprecated setend
> instruction at 0xf76a6bd8
> 
> 
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