linux-kernel - Re: [External] Re: [PATCH 1/3] Revert "riscv/efistub: Ensure GP-relative addressing is not used"

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Message-ID: <CAMj1kXFxzFRQz0BUVw27xdOj+xAVtX9jPjwaLHsEOYDUSqXMOw@mail.gmail.com>
Date: Wed, 6 Mar 2024 14:11:20 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: yunhui cui <cuiyunhui@...edance.com>
Cc: Jan Kiszka <jan.kiszka@...mens.com>, paul.walmsley@...ive.com, palmer@...belt.com, 
	aou@...s.berkeley.edu, xuzhipeng.1973@...edance.com, alexghiti@...osinc.com, 
	samitolvanen@...gle.com, bp@...en8.de, xiao.w.wang@...el.com, 
	kirill.shutemov@...ux.intel.com, nathan@...nel.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-efi@...r.kernel.org
Subject: Re: [External] Re: [PATCH 1/3] Revert "riscv/efistub: Ensure
 GP-relative addressing is not used"

On Wed, 6 Mar 2024 at 14:08, yunhui cui <cuiyunhui@...edance.com> wrote:
>
> Hi Jan,
>
> On Wed, Mar 6, 2024 at 8:52 PM Jan Kiszka <jan.kiszka@...mens.com> wrote:
> >
> > On 06.03.24 09:56, Yunhui Cui wrote:
> > > This reverts commit afb2a4fb84555ef9e61061f6ea63ed7087b295d5.
> > >
> >
> > This comes without a reason - which is likely something around "will fix
> > this properly later". But then you regress first and only fix
> > afterwards. Can't that be done the other way around?
>
> Sorry, I don't quite understand what you mean. Can you help explain it
> more clearly? Do you mean "delete mno-relax instead of revert
> directly?"
>

You should order your patches in a way that does not create
intermediate states (between 1-2 or between 2-3) where the original
problem is being recreated.

So in this case, you should
a) fix the issue
b) revert the existing patches in *opposite* order

However, I don't think the EFI stub can use GP - please refer to my other reply.