From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Borislav Petkov <bp@alien8.de>, Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-s390@vger.kernel.org, linux-efi@vger.kernel.org,
Brijesh Singh <brijesh.singh@amd.com>,
kvm@vger.kernel.org, Tom Lendacky <thomas.lendacky@amd.com>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
x86@kernel.org, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
platform-driver-x86@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
iommu@lists.linux-foundation.org, Andi Kleen <ak@linux.intel.com>,
Paul Mackerras <paulus@samba.org>,
amd-gfx@lists.freedesktop.org, linux-fsdevel@vger.kernel.org,
linux-graphics-maintainer@vmware.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 4/8] powerpc/pseries/svm: Add a powerpc version of cc_platform_has()
Date: Wed, 15 Sep 2021 19:18:34 +0200 [thread overview]
Message-ID: <f8388f18-5e90-5d0f-d681-0b17f8307dd4@csgroup.eu> (raw)
In-Reply-To: <YUHGDbtiGrDz5+NS@zn.tnic>
Le 15/09/2021 à 12:08, Borislav Petkov a écrit :
> On Wed, Sep 15, 2021 at 10:28:59AM +1000, Michael Ellerman wrote:
>> I don't love it, a new C file and an out-of-line call to then call back
>> to a static inline that for most configuration will return false ... but
>> whatever :)
>
> Yeah, hch thinks it'll cause a big mess otherwise:
>
> https://lore.kernel.org/lkml/YSScWvpXeVXw%2Fed5@infradead.org/
Could you please provide more explicit explanation why inlining such an
helper is considered as bad practice and messy ?
Because as demonstrated in my previous response some days ago, taking
that outline ends up with an unneccessary ugly generated code and we
don't benefit front GCC's capability to fold in and opt out unreachable
code.
As pointed by Michael in most cases the function will just return false
so behind the performance concern, there is also the code size and code
coverage topic that is to be taken into account. And even when the
function doesn't return false, the only thing it does folds into a
single powerpc instruction so there is really no point in making a
dedicated out-of-line fonction for that and suffer the cost and the size
of a function call and to justify the addition of a dedicated C file.
>
> I guess less ifdeffery is nice too.
I can't see your point here. Inlining the function wouldn't add any
ifdeffery as far as I can see.
So, would you mind reconsidering your approach and allow architectures
to provide inline implementation by just not enforcing a generic
prototype ? Or otherwise provide more details and exemple of why the
cons are more important versus the pros ?
Thanks
Christophe
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-09-15 17:18 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-08 22:58 [PATCH v3 0/8] Implement generic cc_platform_has() helper function Tom Lendacky via iommu
2021-09-08 22:58 ` [PATCH v3 1/8] x86/ioremap: Selectively build arch override encryption functions Tom Lendacky via iommu
2021-09-08 22:58 ` [PATCH v3 2/8] mm: Introduce a function to check for confidential computing features Tom Lendacky via iommu
2021-09-09 7:35 ` Christophe Leroy
2021-09-10 15:02 ` Borislav Petkov
2021-09-08 22:58 ` [PATCH v3 3/8] x86/sev: Add an x86 version of cc_platform_has() Tom Lendacky via iommu
2021-09-11 10:10 ` Borislav Petkov
2021-09-08 22:58 ` [PATCH v3 4/8] powerpc/pseries/svm: Add a powerpc " Tom Lendacky via iommu
2021-09-09 7:40 ` Christophe Leroy
2021-09-14 11:58 ` Borislav Petkov
2021-09-14 14:47 ` Christophe Leroy
2021-09-14 14:56 ` Borislav Petkov
2021-09-15 0:28 ` Michael Ellerman
2021-09-15 10:08 ` Borislav Petkov
2021-09-15 17:18 ` Christophe Leroy [this message]
2021-09-15 18:47 ` Borislav Petkov
2021-09-16 7:35 ` Christoph Hellwig
2021-09-16 11:51 ` Michael Ellerman
2021-09-08 22:58 ` [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has() Tom Lendacky via iommu
2021-09-14 18:24 ` Borislav Petkov
2021-09-20 19:23 ` Kirill A. Shutemov
2021-09-21 17:04 ` Tom Lendacky via iommu
2021-09-21 17:47 ` Borislav Petkov
2021-09-21 21:20 ` Kirill A. Shutemov
2021-09-21 21:27 ` Borislav Petkov
2021-09-21 21:34 ` Kirill A. Shutemov
2021-09-21 21:43 ` Tom Lendacky via iommu
2021-09-21 21:58 ` Kirill A. Shutemov
2021-09-22 13:40 ` Tom Lendacky via iommu
2021-09-22 14:30 ` Kirill A. Shutemov
2021-09-22 19:52 ` Borislav Petkov
2021-09-22 21:05 ` Kirill A. Shutemov
2021-09-23 18:21 ` Borislav Petkov
2021-09-24 9:41 ` Kirill A. Shutemov
2021-09-24 9:51 ` Borislav Petkov
2021-09-24 13:31 ` Tom Lendacky via iommu
2021-09-08 22:58 ` [PATCH v3 6/8] x86/sev: Replace occurrences of sev_active() " Tom Lendacky via iommu
2021-09-08 22:58 ` [PATCH v3 7/8] x86/sev: Replace occurrences of sev_es_active() " Tom Lendacky via iommu
2021-09-08 22:58 ` [PATCH v3 8/8] treewide: Replace the use of mem_encrypt_active() " Tom Lendacky via iommu
2021-09-09 7:25 ` Christophe Leroy
2021-09-09 13:10 ` Tom Lendacky via iommu
2021-09-09 7:32 ` [PATCH v3 0/8] Implement generic cc_platform_has() helper function Christian Borntraeger
2021-09-09 13:01 ` Tom Lendacky via iommu
2021-09-15 16:46 ` Borislav Petkov
2021-09-15 17:26 ` Kuppuswamy, Sathyanarayanan
2021-09-16 15:02 ` Borislav Petkov
2021-09-16 18:38 ` Kuppuswamy, Sathyanarayanan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f8388f18-5e90-5d0f-d681-0b17f8307dd4@csgroup.eu \
--to=christophe.leroy@csgroup.eu \
--cc=Tianyu.Lan@microsoft.com \
--cc=ak@linux.intel.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=bp@alien8.de \
--cc=brijesh.singh@amd.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@infradead.org \
--cc=iommu@lists.linux-foundation.org \
--cc=kexec@lists.infradead.org \
--cc=kvm@vger.kernel.org \
--cc=linux-efi@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-graphics-maintainer@vmware.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=paulus@samba.org \
--cc=platform-driver-x86@vger.kernel.org \
--cc=thomas.lendacky@amd.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).