Re: [PATCH v3 4/5] tools headers arm64: Update sysreg.h with kernel sources

From: Oliver Upton <oliver.upton@linux.dev>
To: Eric Auger <eauger@redhat.com>
Cc: Mark Brown <broonie@kernel.org>,
	kvm@vger.kernel.org, kvmarm@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-perf-users@vger.kernel.org,
	Jing Zhang <jingzhangos@google.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	James Morse <james.morse@arm.com>, Marc Zyngier <maz@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Ian Rogers <irogers@google.com>,
	Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v3 4/5] tools headers arm64: Update sysreg.h with kernel sources
Date: Thu, 19 Oct 2023 00:06:25 +0000	[thread overview]
Message-ID: <ZTBzAR1KsWuurob7@linux.dev> (raw)
In-Reply-To: <8baca35a-9154-97e6-d682-032fc69d2da6@redhat.com>

Hi Eric,

Thanks for reviewing the series.

On Wed, Oct 18, 2023 at 03:06:12PM +0200, Eric Auger wrote:
> Hi Mark, Oliver,
> 
> On 10/18/23 14:16, Mark Brown wrote:
> > On Wed, Oct 18, 2023 at 01:57:31PM +0200, Eric Auger wrote:
> >> On 10/11/23 21:57, Oliver Upton wrote:
> > 
> >>>  #define set_pstate_pan(x)		asm volatile(SET_PSTATE_PAN(x))
> >>>  #define set_pstate_uao(x)		asm volatile(SET_PSTATE_UAO(x))
> >>>  #define set_pstate_ssbs(x)		asm volatile(SET_PSTATE_SSBS(x))
> >>> +#define set_pstate_dit(x)		asm volatile(SET_PSTATE_DIT(x))
> > 
> >> could you comment on the *DIT* addictions, what is it for?
> > 
> > DIT is data independent timing, this tells the processor to ensure that
> > instructions take a constant time regardless of the data they are
> > handling.
> 
> > 
> > Note that this file is just a copy of arch/arm64/include/asm/gpr-num.h,
> > the main purpose here is to sync with the original.
> 
> Ah thanks. that's helpful for me to understand where this gpr-num.h
> comes from. This could be documented in the commit msg though.
> 
> Something like:
> 
> adding tools/arch/arm64/include/asm/gpr-num.h matching linux
> arch/arm64/include/asm/gpr-num.h
> 
> and syncing tools/arch/arm64/include/asm/sysreg.h with the fellow header
> in the linux tree.

Yeah, I could've spelled it out a bit more. I already cracked this off
of an even larger patch from before I picked up the series because the
diff was massive.

> tbh I did not initially understand that all this diffstat was aimed to
> match the linux arch/arm64/include/asm/sysreg.h. Now diffing both I have
> some diffs. Doesn't it need a refresh?

I'm worried it is a fool's errand at this point to keep the two in sync,
as I'm sure there will be more in -rc1. The tools copy of sysreg.h isn't
a verbatim copy either, there are some deliberate deletions in there as
well.

I've taken this as is, we can always come back and update the headers
afterwards if we find a need for it

-- 
Thanks,
Oliver