linux-kernel - Re: [PATCH v3 2/2] arm64/sysreg: Convert HFGITR

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Message-ID: <20230406150456.GA11802@willie-the-truck>
Date:   Thu, 6 Apr 2023 16:04:57 +0100
From:   Will Deacon <will@...nel.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Joey Gouly <joey.gouly@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] arm64/sysreg: Convert HFGITR_EL2 to automatic
 generation

On Thu, Apr 06, 2023 at 04:02:18PM +0100, Mark Brown wrote:
> On Thu, Apr 06, 2023 at 03:46:54PM +0100, Will Deacon wrote:
> > On Thu, Mar 23, 2023 at 08:44:54PM +0000, Mark Brown wrote:
> 
> > > Automatically generate the Hypervisor Fine-Grained Instruction Trap
> > > Register as per DDI0601 2022-12, currently we only have a definition for
> > > the register name not any of the contents.  No functional change.
> 
> > > +Res0	63:61
> > > +Field	60	COSPRCTX
> > > +Field	59	nGCSEPP
> > > +Field	58	nGCSSTR_EL1
> > > +Field	57	nGCSPUSHM_EL1
> 
> > These aren't in the Arm ARM afaict ^^^
> 
> Yes, as mentioned in the cover letter these are as per DDI0601 2022-12,
> the current at time of posting the patch latest release of the
> architecture XML.  They should appear in the next release of the ARM,
> the XML is updated more frequently.  The XML can be seen on the web
> here:
> 
>     https://developer.arm.com/documentation/ddi0601/2022-12/AArch64-Registers/HFGITR-EL2--Hypervisor-Fine-Grained-Instruction-Trap-Register?lang=en

Thanks -- I just wanted to check that they were final. Happy to trust that
xml.

> > Can't we generate this file from the architecture xml? That would hopefully
> > avoid typos like this and make review less tedious.
> 
> I agree that this seems like a sensible idea however there has
> previously been pushback on the idea of providing tooling to do that,
> and we would want to manually integrate the output of any such tool
> since there are a number of cases where for legacy or usability reasons
> we rename or combine fields.  The cases where we use a Fields block to
> cover identical ELx versions are another issue.
> 
> I also note that while the XML is viewable on the web AFAICT the only
> directly downloadable version of the architecture XML available
> externally is in PDF format which is not entirely helpful for this
> purpose.

Sorry, I didn't mean to automate this in the tree, just that you could
do it locally when you generate the patch (as I suspect this must be
tedious for you to write out by hand too!). We've had a string of typos
in the definitions so far, and it would be nice to take steps to avoid
that for future changes.

Will