Re: The killing of ideal_nops[]

2021-03-14 Thread Maciej W. Rozycki
On Wed, 10 Mar 2021, Peter Zijlstra wrote: > Below is the latest version which I just pushed out to my git tree so > that the robots can have a go at it. Do you want me to quickly check it with a real i486, or is it already covered by said robots (NB I wouldn't trust QEMU with such stuff)? M

RE: The killing of ideal_nops[]

2021-03-11 Thread David Laight
From: Peter Zijlstra ... > Below is the latest version which I just pushed out to my git tree so > that the robots can have a go at it. Why not delete the indirection table? So you end up with: > +#ifndef CONFIG_64BIT > + > +/* > + * Generic 32bit nops from GAS: > + * > + * 1: nop > + * 2: movl

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 07:48:08AM -0800, Alexei Starovoitov wrote: > Ack for bpf bits. Thanks! > I think the cleanup is good from the point of having one way to do things. Right, that was the motivation. Currently x86 is the sole architecture (and thus weird and more complicated) where NOPs var

Re: The killing of ideal_nops[]

2021-03-10 Thread Alexei Starovoitov
On Wed, Mar 10, 2021 at 6:29 AM Peter Zijlstra wrote: > > On Wed, Mar 10, 2021 at 09:13:24AM -0500, Steven Rostedt wrote: > > On Wed, 10 Mar 2021 11:22:48 +0100 > > Peter Zijlstra wrote: > > > > > After this FEATURE_NOPL is unused except for required-features for > > > x86_64. FEATURE_K8 is only

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 03:24:47PM +0100, Peter Zijlstra wrote: > On Wed, Mar 10, 2021 at 09:13:24AM -0500, Steven Rostedt wrote: > > On Wed, 10 Mar 2021 11:22:48 +0100 > > Peter Zijlstra wrote: > > > > > After this FEATURE_NOPL is unused except for required-features for > > > x86_64. FEATURE_K8

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 09:13:24AM -0500, Steven Rostedt wrote: > On Wed, 10 Mar 2021 11:22:48 +0100 > Peter Zijlstra wrote: > > > After this FEATURE_NOPL is unused except for required-features for > > x86_64. FEATURE_K8 is only used for PTI and FEATURE_K7 is unused. > > > > AFAICT this negative

Re: The killing of ideal_nops[]

2021-03-10 Thread Steven Rostedt
On Wed, 10 Mar 2021 11:22:48 +0100 Peter Zijlstra wrote: > After this FEATURE_NOPL is unused except for required-features for > x86_64. FEATURE_K8 is only used for PTI and FEATURE_K7 is unused. > > AFAICT this negatively affects lots of 32bit (DONTCARE) and 32bit on > 64bit CPUs (CARELESS) and e

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 11:03:10AM +0100, Peter Zijlstra wrote: > -void __init arch_init_ideal_nops(void) > -{ > - switch (boot_cpu_data.x86_vendor) { > - case X86_VENDOR_INTEL: > - /* > - * Due to a decoder implementation quirk, some > - * specific Int

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 10:35:45AM +0100, Peter Zijlstra wrote: > On Wed, Mar 10, 2021 at 10:14:35AM +0100, Peter Zijlstra wrote: > > Sure, but we can have one set on 32bit and another set on 64bit. > > > Although I would use DS prefix nops for 32bit nop5/nop8 to keep them > > single instructions.

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Wed, Mar 10, 2021 at 10:14:35AM +0100, Peter Zijlstra wrote: > Sure, but we can have one set on 32bit and another set on 64bit. > Although I would use DS prefix nops for 32bit nop5/nop8 to keep them > single instructions. > > Then we can do away with runtime nop selection and special atomic no

Re: The killing of ideal_nops[]

2021-03-10 Thread Peter Zijlstra
On Tue, Mar 09, 2021 at 04:33:45PM -0800, h...@zytor.com wrote: > On March 9, 2021 1:24:44 PM PST, Peter Zijlstra wrote: > >On Tue, Mar 09, 2021 at 12:05:19PM -0500, Steven Rostedt wrote: > >> On Tue, 9 Mar 2021 17:58:17 +0100 > >> Peter Zijlstra wrote: > >> > >> > Hi, > >> > > >> > AFAICT ever

Re: The killing of ideal_nops[]

2021-03-09 Thread hpa
On March 9, 2021 1:24:44 PM PST, Peter Zijlstra wrote: >On Tue, Mar 09, 2021 at 12:05:19PM -0500, Steven Rostedt wrote: >> On Tue, 9 Mar 2021 17:58:17 +0100 >> Peter Zijlstra wrote: >> >> > Hi, >> > >> > AFAICT everything made in the past 10 years ends up using p6_nops. >Is it >> > time to kill

Re: The killing of ideal_nops[]

2021-03-09 Thread Peter Zijlstra
On Tue, Mar 09, 2021 at 12:05:19PM -0500, Steven Rostedt wrote: > On Tue, 9 Mar 2021 17:58:17 +0100 > Peter Zijlstra wrote: > > > Hi, > > > > AFAICT everything made in the past 10 years ends up using p6_nops. Is it > > time to kill off ideal_nops[] and simplify life? > > > > Well, the one bug

Re: The killing of ideal_nops[]

2021-03-09 Thread Steven Rostedt
On Tue, 9 Mar 2021 17:58:17 +0100 Peter Zijlstra wrote: > Hi, > > AFAICT everything made in the past 10 years ends up using p6_nops. Is it > time to kill off ideal_nops[] and simplify life? > Well, the one bug that was reported recently was due to a box that uses a different "ideal_nops" than

The killing of ideal_nops[]

2021-03-09 Thread Peter Zijlstra
Hi, AFAICT everything made in the past 10 years ends up using p6_nops. Is it time to kill off ideal_nops[] and simplify life?