linux-kernel - Re: [PATCH 06/14] KVM: selftests: Rename UNAME_M to ARCH

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Message-ID: <Y5jadzKz6Qi9MiI9@google.com>
Date:   Tue, 13 Dec 2022 20:03:03 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Tom Rix <trix@...hat.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, linux-riscv@...ts.infradead.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Ricardo Koller <ricarkol@...gle.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Raghavendra Rao Ananta <rananta@...gle.com>
Cc:     David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH 06/14] KVM: selftests: Rename UNAME_M to ARCH_DIR, fill
 explicitly for x86

+David

On Tue, Dec 13, 2022, Sean Christopherson wrote:
> Rename UNAME_M to ARCH_DIR and explicitly set it directly for x86.  At
> this point, the name of the arch directory really doesn't have anything
> to do with `uname -m`, and UNAME_M is unnecessarily confusing given that
> its purpose is purely to identify the arch specific directory.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> -# No change necessary for x86_64
> -UNAME_M := $(shell uname -m)
> -
> -# Set UNAME_M for arm64 compile/install to work
> -ifeq ($(ARCH),arm64)
> -	UNAME_M := aarch64
> -endif
> -# Set UNAME_M s390x compile/install to work
> -ifeq ($(ARCH),s390)
> -	UNAME_M := s390x
> -endif
> -# Set UNAME_M riscv compile/install to work
> -ifeq ($(ARCH),riscv)
> -	UNAME_M := riscv
> +ifeq ($(ARCH),x86)

As discovered by by David, this breaks doing "ARCH=x86_64 make", which is an
allowed/supported variant in the kernel proper, so this needs to be:

  ifneq (,$(filter $(ARCH),x86 x86_64))

or alternatively

  ifeq ($(ARCH),x86_64)
  ARCH := x86
  endif

Hmm, unless there's a reason to keep ARCH=x86_64, the latter appears to be the
better option as lib.mak doesn't play nice with x86_64 either, e.g. `ARCH=x86_64
LLVM=1 make` fails.  That's arguably a lib.mak bug, but it's trivial to handle
in KVM's makefile so forcing lib.mak to handle both seems unnecessary.

I'll also add a comment to call out that $(ARCH) follows the kernel's terminology
for arch/*, whereas for whatever reason KVM selftests effectively uses `uname -m`
terminology.

One last thought/question, what do y'all think about renaming directories to
follow the kernel proper?  I.e. aarch64=>arm64, s390x=>s390, and x86_64=>x86.
Then $(ARCH_DIR) would go away.  The churn would be unfortunate, but it would be
nice to align with arch/ and tools/arch/.

> +	ARCH_DIR := x86_64
> +else ifeq ($(ARCH),arm64)
> +	ARCH_DIR := aarch64
> +else ifeq ($(ARCH),s390)
> +	ARCH_DIR := s390x
> +else ifeq ($(ARCH),riscv)
> +	ARCH_DIR := riscv
> +else
> +$(error Unknown architecture '$(ARCH)')
>  endif