LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Juergen Gross <jgross@suse.com>
To: Eial Czerwacki <eial@scalemp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Shai Fultheim (Shai@ScaleMP.com)" <Shai@ScaleMP.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"mhocko@suse.cz" <mhocko@suse.cz>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	"linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"mm-commits@vger.kernel.org" <mm-commits@vger.kernel.org>,
	X86 ML <x86@kernel.org>, 'Oren Twaig' <oren@scalemp.com>
Subject: Re: [PATCH] x86/build: Build VSMP support only if selected
Date: Thu, 1 Nov 2018 16:39:13 +0100	[thread overview]
Message-ID: <0d472636-e39d-8cd3-4a47-2b9dc139b7fe@suse.com> (raw)
In-Reply-To: <3c75860d-e3d7-8c28-6120-f6056200f941@scalemp.com>

On 01/11/2018 16:09, Eial Czerwacki wrote:
> Greetings,
> 
> On 11/01/2018 03:45 PM, Juergen Gross wrote:
>> On 01/11/2018 14:10, Eial Czerwacki wrote:
>>> Greetings,
>>>
>>> On 11/01/2018 12:39 PM, Shai Fultheim (Shai@ScaleMP.com) wrote:
>>>> On 01/11/18 11:37, Thomas Gleixner wrote:
>>>>
>>>>> VSMP support is built even if CONFIG_X86_VSMP is not set. This leads to a build
>>>>> breakage when CONFIG_PCI is disabled as well.
>>>>>
>>>>> Build VSMP code only when selected.
>>>>
>>>> This patch disables detect_vsmp_box() on systems without CONFIG_X86_VSMP, due to
>>>> the recent 6da63eb241a05b0e676d68975e793c0521387141.  This is significant
>>>> regression that will affect significant number of deployments.
>>>>
>>>> We will reply shortly with an updated patch that fix the dependency on pv_irq_ops,
>>>> and revert to CONFIG_PARAVIRT, with proper protection for CONFIG_PCI.
>>>>
>>>
>>> here is the proper patch which fixes the issue on hand:
>>> From ebff534f8cfa55d7c3ab798c44abe879f3fbe2b8 Mon Sep 17 00:00:00 2001
>>> From: Eial Czerwacki <eial@scalemp.com>
>>> Date: Thu, 1 Nov 2018 15:08:32 +0200
>>> Subject: [PATCH] x86/build: Build VSMP support only if CONFIG_PCI is
>>> selected
>>>
>>> vsmp dependency of pv_irq_ops removed some years ago, so now let's clean
>>> it up from vsmp_64.c.
>>>
>>> In short, "cap & ctl & (1 << 4)" was always returning 0, as such we can
>>> remove all the PARAVIRT/PARAVIRT_XXL code handling that.
>>>
>>> However, the rest of the code depends on CONFIG_PCI, so fix it accordingly.
>>>
>>> Signed-off-by: Eial Czerwacki <eial@scalemp.com>
>>> Acked-by: Shai Fultheim <shai@scalemp.com>
>>> ---
>>>  arch/x86/Kconfig          |  1 -
>>>  arch/x86/kernel/vsmp_64.c | 80
>>> +++--------------------------------------------
>>>  2 files changed, 5 insertions(+), 76 deletions(-)
>>>
>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>> index c51c989..4b187ca 100644
>>> --- a/arch/x86/Kconfig
>>> +++ b/arch/x86/Kconfig
>>> @@ -524,7 +524,6 @@ config X86_VSMP
>>>         bool "ScaleMP vSMP"
>>>         select HYPERVISOR_GUEST
>>>         select PARAVIRT
>>
>> Do you really still need PARAVIRT and HYPERVISOR_GUEST?
>> Maybe you want IRQ_REMAP instead?
>>
> Better performance is achieved with PARAVIRTed kernel.   Hence we keep
> them both in.

Do you have an explanation for that? Normally PARAVIRT is expected
to have a small negative impact on performance.


Juergen

      reply	other threads:[~2018-11-01 15:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-30 23:09 mmotm 2018-10-30-16-08 uploaded akpm
2018-10-31  3:20 ` mmotm 2018-10-30-16-08 uploaded (arch/x86/kernel/vsmp_64.c) Randy Dunlap
2018-11-01  9:36   ` [PATCH] x86/build: Build VSMP support only if selected Thomas Gleixner
2018-11-01 10:39     ` Shai Fultheim (Shai@ScaleMP.com)
2018-11-01 13:10       ` Eial Czerwacki
2018-11-01 13:17         ` Thomas Gleixner
2018-11-01 13:45         ` Juergen Gross
2018-11-01 15:09           ` Eial Czerwacki
2018-11-01 15:39             ` Juergen Gross [this message]

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=0d472636-e39d-8cd3-4a47-2b9dc139b7fe@suse.com \
    --to=jgross@suse.com \
    --cc=Shai@ScaleMP.com \
    --cc=akpm@linux-foundation.org \
    --cc=broonie@kernel.org \
    --cc=eial@scalemp.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-next@vger.kernel.org \
    --cc=mhocko@suse.cz \
    --cc=mm-commits@vger.kernel.org \
    --cc=oren@scalemp.com \
    --cc=rdunlap@infradead.org \
    --cc=sfr@canb.auug.org.au \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] x86/build: Build VSMP support only if selected' \
    /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

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).