All of lore.kernel.org
 help / color / mirror / Atom feed
From: Paul Mackerras <paulus@ozlabs.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management
Date: Tue, 29 Aug 2017 10:13:19 +1000	[thread overview]
Message-ID: <20170829001319.GE12629@fergus.ozlabs.ibm.com> (raw)
In-Reply-To: <20170825043036.18236-2-npiggin@gmail.com>

On Fri, Aug 25, 2017 at 02:30:33PM +1000, Nicholas Piggin wrote:
> POWER9 CPUs have independent MMU contexts per thread, so KVM does not
> need to quiesce secondary threads, so the hwthread_req/hwthread_state
> protocol does not have to be used. So patch it away on POWER9, and patch
> away the branch from the Linux idle wakeup to kvm_start_guest that is
> never used.
> 
> Add a warning and error out of kvmppc_grab_hwthread in case it is ever
> called on POWER9.
> 
> This avoids a hwsync in the idle wakeup path on POWER9.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Some of the feature sections seem a little unnecessary except for
documentation purposes (e.g. the second one added after the
kvm_no_guest label), but they won't actually hurt, so:

Acked-by: Paul Mackerras <paulus@ozlabs.org>

WARNING: multiple messages have this Message-ID (diff)
From: Paul Mackerras <paulus@ozlabs.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management
Date: Tue, 29 Aug 2017 00:13:19 +0000	[thread overview]
Message-ID: <20170829001319.GE12629@fergus.ozlabs.ibm.com> (raw)
In-Reply-To: <20170825043036.18236-2-npiggin@gmail.com>

On Fri, Aug 25, 2017 at 02:30:33PM +1000, Nicholas Piggin wrote:
> POWER9 CPUs have independent MMU contexts per thread, so KVM does not
> need to quiesce secondary threads, so the hwthread_req/hwthread_state
> protocol does not have to be used. So patch it away on POWER9, and patch
> away the branch from the Linux idle wakeup to kvm_start_guest that is
> never used.
> 
> Add a warning and error out of kvmppc_grab_hwthread in case it is ever
> called on POWER9.
> 
> This avoids a hwsync in the idle wakeup path on POWER9.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Some of the feature sections seem a little unnecessary except for
documentation purposes (e.g. the second one added after the
kvm_no_guest label), but they won't actually hurt, so:

Acked-by: Paul Mackerras <paulus@ozlabs.org>

  parent reply	other threads:[~2017-08-29  0:20 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-25  4:30 [PATCH v3 0/4] powerpc/64s: idle POWER9 stop improvements Nicholas Piggin
2017-08-25  4:30 ` Nicholas Piggin
2017-08-25  4:30 ` [PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management Nicholas Piggin
2017-08-25  4:30   ` Nicholas Piggin
2017-08-28 11:49   ` Michael Ellerman
2017-08-28 11:49     ` Michael Ellerman
2017-08-29  0:13   ` Paul Mackerras [this message]
2017-08-29  0:13     ` Paul Mackerras
2017-08-31 11:36   ` [v3, " Michael Ellerman
2017-08-31 11:36     ` Michael Ellerman
2017-08-25  4:30 ` [PATCH v3 2/4] powerpc/64s: idle POWER9 can execute stop without a sync sequence Nicholas Piggin
2017-08-25  4:30   ` Nicholas Piggin
2017-08-29  0:11   ` Paul Mackerras
2017-08-29  0:11     ` Paul Mackerras
2017-08-29 10:30     ` Michael Ellerman
2017-08-29 10:30       ` Michael Ellerman
2017-08-31 11:36   ` [v3, " Michael Ellerman
2017-08-31 11:36     ` Michael Ellerman
2017-08-25  4:30 ` [PATCH v3 3/4] powerpc/64s: idle POWER9 can execute stop in virtual mode Nicholas Piggin
2017-08-25  4:30   ` Nicholas Piggin
2017-08-29  0:14   ` Paul Mackerras
2017-08-29  0:14     ` Paul Mackerras
2017-08-31 11:36   ` [v3, " Michael Ellerman
2017-08-31 11:36     ` [v3,3/4] " Michael Ellerman
2017-08-25  4:30 ` [PATCH v3 4/4] powerpc/64s: idle ESL=0 stop can avoid MSR and save/restore overhead Nicholas Piggin
2017-08-25  4:30   ` Nicholas Piggin
2017-08-29  0:20   ` Paul Mackerras
2017-08-29  0:20     ` Paul Mackerras
2017-08-29  1:39     ` Nicholas Piggin
2017-08-29  1:39       ` Nicholas Piggin
2017-08-30 11:25   ` Michael Ellerman
2017-08-30 11:25     ` Michael Ellerman
2017-08-30 12:10     ` Nicholas Piggin
2017-08-30 12:10       ` Nicholas Piggin
2017-09-01  9:39       ` Michael Ellerman
2017-09-01  9:39         ` Michael Ellerman
2017-09-20 13:56         ` Nicholas Piggin
2017-09-20 13:56           ` Nicholas Piggin

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=20170829001319.GE12629@fergus.ozlabs.ibm.com \
    --to=paulus@ozlabs.org \
    --cc=kvm-ppc@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=npiggin@gmail.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.