From: David Gibson <david@gibson.dropbear.id.au>
To: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>,
Alexey Kardashevskiy <aik@ozlabs.ru>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Neuling <mikey@neuling.org>,
Alexander Graf <agraf@suse.de>,
linuxppc-dev@lists.ozlabs.org, qemu-devel@nongnu.org,
qemu-ppc@nongnu.org
Subject: Re: [PATCH] spapr: Don't set the TM ibm,pa-features bit in PR KVM mode
Date: Tue, 5 Apr 2016 14:09:41 +1000 [thread overview]
Message-ID: <20160405040941.GT16485@voom.fritz.box> (raw)
In-Reply-To: <20160405021201.GA2663@yogo.paulus.ozlabs.org>
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On Tue, Apr 05, 2016 at 12:12:01PM +1000, Paul Mackerras wrote:
> On Mon, Apr 04, 2016 at 09:09:28PM +1000, Anton Blanchard wrote:
> > We don't support transactional memory in PR KVM, so don't tell
> > the OS that we do.
>
> This assumes PR KVM won't ever support TM, which is hopefully not
> true. If PR KVM does get TM support in future, then QEMU will have no
> clear way to know whether it needs to clear the pa-features bit or
> not. I think we need to define some way for the KVM implementation to
> tell qemu which of these kinds of CPU features it supports.
Yeah, I think we need some sort of capability flag for this. We also
need to isolate this KVM capability testing better into the KVM code,
so we won't break things on TCG.
Speaking of which... I don't imagine we implement TM instructions in
TCG either, so we should probably make sure TM isn't advertised there
either.
> However, we could defer implementing that mechanism until PR KVM does
> get support for TM, I guess. In that case this patch could go in now,
> though it seems slightly icky to be using the pvinfo stuff to
> distinguish PR from HV.
It is icky, but it's the best idiom we have for distinguishing PR
KVM. We try to only do it as a fallback when we can't determine
availability of the specific feature based on a capability, though.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2016-04-05 5:48 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-04 6:44 PR KVM and TM issues Anton Blanchard
2016-04-04 7:00 ` Alexey Kardashevskiy
2016-04-04 10:43 ` Anton Blanchard
2016-04-04 11:09 ` [PATCH] spapr: Don't set the TM ibm,pa-features bit in PR KVM mode Anton Blanchard
2016-04-04 11:13 ` [PATCH] spapr: Don't set the TM ibm, pa-features " Alexander Graf
2016-04-30 0:48 ` [PATCH v2] spapr: Don't set the TM ibm,pa-features " Anton Blanchard
2016-05-02 9:36 ` [Qemu-devel] [PATCH v2] spapr: Don't set the TM ibm, pa-features " haris iqbal
2016-05-27 4:52 ` David Gibson
2016-06-07 12:28 ` [PATCH 1/2] Add PowerPC AT_HWCAP2 definitions Anton Blanchard
2016-06-07 12:32 ` [PATCH 2/2] spapr: Better handling of ibm,pa-features TM bit Anton Blanchard
2016-06-08 2:26 ` David Gibson
2016-07-05 5:19 ` [PATCH 0/3] Rework spapr: Better handling of ibm, pa-features " Sam Bobroff
2016-07-05 5:19 ` [PATCH 1/3] spapr: Disable ibm, pa-features HTM bit Sam Bobroff
2016-07-05 5:51 ` David Gibson
2016-07-05 5:19 ` [PATCH 2/3] Add KVM_CAP_PPC_HTM to linux/kvm.h Sam Bobroff
2016-07-05 6:05 ` David Gibson
2016-07-06 4:41 ` Sam Bobroff
2016-07-06 5:09 ` David Gibson
2016-07-05 5:19 ` [PATCH 3/3] spapr: Set ibm, pa-features HTM from KVM_CAP_PPC_HTM Sam Bobroff
2016-07-05 6:52 ` David Gibson
2016-07-06 5:35 ` [PATCH v2 0/3] Rework spapr: Better handling of ibm, pa-features TM bit Sam Bobroff
2016-07-06 5:35 ` [PATCH v2 1/3] spapr: Disable ibm, pa-features HTM bit Sam Bobroff
2016-07-07 4:38 ` David Gibson
2016-07-06 5:35 ` [PATCH v2 2/3] Add KVM_CAP_PPC_HTM to linux/kvm.h Sam Bobroff
2016-07-07 4:38 ` David Gibson
2016-07-06 5:35 ` [PATCH v2 3/3] spapr: Set ibm, pa-features HTM from KVM_CAP_PPC_HTM Sam Bobroff
2016-07-07 4:39 ` David Gibson
2016-06-08 2:19 ` [PATCH 1/2] Add PowerPC AT_HWCAP2 definitions David Gibson
2016-04-05 2:12 ` [PATCH] spapr: Don't set the TM ibm,pa-features bit in PR KVM mode Paul Mackerras
2016-04-05 4:09 ` David Gibson [this message]
2016-04-05 7:33 ` Alexey Kardashevskiy
2016-04-04 11:11 ` [PATCH] powerpc: Clear user CPU feature bits if TM is disabled at runtime Anton Blanchard
2016-04-05 0:52 ` David Gibson
2016-04-05 9:35 ` Michael Ellerman
2016-04-05 9:56 ` Benjamin Herrenschmidt
2016-04-05 22:40 ` Michael Ellerman
2016-04-15 2:06 ` [PATCH 1/3] powerpc: scan_features() updates incorrect bits Anton Blanchard
2016-04-15 14:27 ` [1/3] " Michael Ellerman
2016-04-18 4:40 ` Michael Ellerman
2016-04-18 4:16 ` Michael Ellerman
2016-04-18 10:36 ` [PATCH v2 1/3] powerpc: scan_features() updates incorrect bits for REAL_LE Michael Ellerman
2016-04-19 10:09 ` [v2, " Michael Ellerman
2016-04-15 2:07 ` [PATCH 2/3] powerpc: Update cpu_user_features2 in scan_features() Anton Blanchard
2016-04-19 10:09 ` [2/3] " Michael Ellerman
2016-04-15 2:08 ` [PATCH 3/3] powerpc: Update TM user feature bits " Anton Blanchard
2016-04-19 10:09 ` [3/3] " Michael Ellerman
2016-04-04 11:09 ` PR KVM and TM issues Michael Neuling
2016-04-05 7:29 ` Alexey Kardashevskiy
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