From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
Cc: Alexander Graf <agraf@suse.de>,
"tiejun.chen" <tiejun.chen@windriver.com>,
"<kvm-ppc@vger.kernel.org>" <kvm-ppc@vger.kernel.org>,
"<kvm@vger.kernel.org> list" <kvm@vger.kernel.org>
Subject: Re: [v1][PATCH 1/1] KVM: PPC: disable preemption when using hard_irq_disable()
Date: Fri, 12 Jul 2013 10:30:27 +1000 [thread overview]
Message-ID: <1373589027.19894.128.camel@pasglop> (raw)
In-Reply-To: <1373559480.8183.258@snotra>
On Thu, 2013-07-11 at 11:18 -0500, Scott Wood wrote:
>
> If we set IRQs as soft-disabled prior to calling hard_irq_disable(),
> then hard_irq_disable() will fail to call trace_hardirqs_off().
Sure because setting them as soft-disabled will have done it.
However by doing so, you also create the possibility of latching a new
event in irq_happened.
> > or by disabling preemption until we enter the guest for real.
>
> I don't follow this one. We're exiting, not entering.
>
> > Any preferences?
>
> Use arch_local_save_flags() in hard_irq_disable() instead of reading
> soft_enabled with C code.
That or just use local_paca... Though we'd had problems in the past
where gcc would defeat us there and essentially copy r13 to another
register and start indexing from there. That kills you if you preempt.
Cheers,
Ben.
next parent reply other threads:[~2013-07-12 0:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1373559480.8183.258@snotra>
2013-07-12 0:30 ` Benjamin Herrenschmidt [this message]
[not found] ` <FB21594A-C233-4A97-8503-E2A1275F8F17@suse.de>
[not found] ` <1373560585.8183.261@snotra>
2013-07-12 3:22 ` [v1][PATCH 1/1] KVM: PPC: disable preemption when using hard_irq_disable() tiejun.chen
[not found] <1373651433.8183.276@snotra>
2013-07-12 23:05 ` Benjamin Herrenschmidt
2013-07-15 2:20 ` tiejun.chen
2013-07-15 2:47 ` Benjamin Herrenschmidt
2013-07-15 3:03 ` tiejun.chen
[not found] ` <1373909248.8183.303@snotra>
2013-07-16 2:15 ` tiejun.chen
2013-07-15 2:25 ` tiejun.chen
2013-07-10 6:02 Tiejun Chen
2013-07-10 9:49 ` Alexander Graf
2013-07-11 2:48 ` tiejun.chen
2013-07-11 9:49 ` Alexander Graf
2013-07-11 12:28 ` Benjamin Herrenschmidt
2013-07-11 12:47 ` Alexander Graf
2013-07-11 12:54 ` Benjamin Herrenschmidt
2013-07-11 13:07 ` Alexander Graf
2013-07-12 0:19 ` Benjamin Herrenschmidt
2013-07-12 2:13 ` tiejun.chen
2013-07-12 3:57 ` Benjamin Herrenschmidt
2013-07-12 4:54 ` tiejun.chen
2013-07-14 4:13 ` Benjamin Herrenschmidt
2013-07-15 3:04 ` tiejun.chen
2013-07-10 19:15 ` Scott Wood
2013-07-11 3:00 ` tiejun.chen
2013-07-11 14:13 ` Scott Wood
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