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From: Andrew Jones To: Alexandru Elisei Cc: eric.auger@redhat.com, lvivier@redhat.com, thuth@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, nrb@linux.ibm.com, david@redhat.com, pbonzini@redhat.com, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-s390@vger.kernel.org, vladimir.murzin@arm.com Subject: Re: [kvm-unit-tests PATCH v1 2/5] configure: Display the default processor for arm and arm64 Message-ID: <20250115-dde4d782f94a79819c861c3b@orel> References: <20250110135848.35465-1-alexandru.elisei@arm.com> <20250110135848.35465-3-alexandru.elisei@arm.com> <20250113-45b57478be2241a35ffa1b67@orel> <20250114-a36510d222fc3410b9b7654e@orel> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Wed, Jan 15, 2025 at 09:55:14AM +0000, Alexandru Elisei wrote: > Hi Drew, > > On Tue, Jan 14, 2025 at 07:51:04PM +0100, Andrew Jones wrote: > > On Tue, Jan 14, 2025 at 05:17:28PM +0000, Alexandru Elisei wrote: > > ... > > > > > +# $arch will have changed when cross-compiling. > > > > > +[ -z "$processor" ] && processor=$(get_default_processor $arch) > > > > > > > > The fact that $arch and $processor are wrong until they've had a chance to > > > > > > $processor is never wrong. $processor is unset until either the user sets it > > > with --processor, or until this line. This patch introduces $default_processor > > > only for the purpose of having an accurate help text, it doesn't change when and > > > how $processor is assigned. > > > > I should have said "The fact that $arch and $default_processor are wrong..." > > > > > > > > > be converted might be another reason for the $do_help idea. But it'll > > > > always be fragile since another change that does some sort of conversion > > > > could end up getting added after the '[ $do_help ] && usage' someday. > > > > > > configure needs to distinguish between: > > > > > > 1. The user not having specified --processor when doing ./configure. > > > 2. The user having set --processor. > > > > > > If 1, then kvm-unit-tests can use the default $processor value for $arch, > > > which could have also been specified by the user. > > > > > > If 2, then kvm-unit-tests should not touch $processor because that's what the > > > user wants. > > > > > > Do you see something wrong with that reasoning? > > > > If we output $default_processor in usage() before it's had a chance to be > > set correctly based on a given cross arch, then it won't display the > > correct name. > > > > > > > > Also, I don't understand why you say it's fragile, since configure doesn't > > > > I wrote "it'll always be fragile" where 'it' refers to the most recent > > object of my paragraph ("the $do_help idea"). But, TBH, I'm not sure > > how important it is to get the help text accurate, so we can just not > > care if we call usage() with the wrong strings sometimes. > > Got it now, thanks for explaining it. > > My opinion is that a help text is there to help the user, and in my experience > an inaccurate help text can be very frustrating - think comments that say > one thing, and the code does something else. > > How about this: > > diff --git a/configure b/configure > index 3ab0ec208e10..5dbe189816b2 100755 > --- a/configure > +++ b/configure > @@ -51,7 +51,6 @@ page_size= > earlycon= > efi= > efi_direct= > -default_processor=$(get_default_processor $arch) > > # Enable -Werror by default for git repositories only (i.e. developer builds) > if [ -e "$srcdir"/.git ]; then > @@ -61,13 +60,14 @@ else > fi > > usage() { > + [ -z "$processor" ] && processor=$(get_default_processor $arch) > cat <<-EOF > Usage: $0 [options] > > Options include: > --arch=ARCH architecture to compile for ($arch). ARCH can be one of: > arm, arm64/aarch64, i386, ppc64, riscv32, riscv64, s390x, x86_64 > - --processor=PROCESSOR processor to compile for ($default_processor). For arm and arm64, the > + --processor=PROCESSOR processor to compile for ($processor). For arm and arm64, the > value 'max' is special and it will be passed directly to > qemu, bypassing the compiler. In this case, --cflags can be > used to compile for a specific processor. > > Should be accurate enough, as far as I can tell. And I don't think there's > a need for $do_help: if the user does ./configure --help --arch=arm64, then > I think it's reasonable to expect that --help will be interpreted before > --arch is parsed. > Sounds good. Thanks, drew