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>
next prev parent reply other threads:[~2017-08-29 0:20 UTC|newest]
Thread overview: 19+ 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 ` [PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management Nicholas Piggin
2017-08-28 11:49 ` Michael Ellerman
2017-08-29 0:13 ` Paul Mackerras [this message]
2017-08-31 11:36 ` [v3, " Michael Ellerman
2017-08-25 4:30 ` [PATCH v3 2/4] powerpc/64s: idle POWER9 can execute stop without a sync sequence Nicholas Piggin
2017-08-29 0:11 ` Paul Mackerras
2017-08-29 10:30 ` Michael Ellerman
2017-08-31 11:36 ` [v3, " Michael Ellerman
2017-08-25 4:30 ` [PATCH v3 3/4] powerpc/64s: idle POWER9 can execute stop in virtual mode Nicholas Piggin
2017-08-29 0:14 ` Paul Mackerras
2017-08-31 11:36 ` [v3, " 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
2017-08-29 0:20 ` Paul Mackerras
2017-08-29 1:39 ` Nicholas Piggin
2017-08-30 11:25 ` Michael Ellerman
2017-08-30 12:10 ` Nicholas Piggin
2017-09-01 9:39 ` Michael Ellerman
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 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).