From: Scott Wood <scottwood@freescale.com>
To: Scott Wood <scottwood@freescale.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
Alexander Graf <agraf@suse.de>,
kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 1/3] kvm/ppc/booke: Hold srcu lock when calling gfn functions
Date: Thu, 02 May 2013 00:30:04 +0000 [thread overview]
Message-ID: <1367454604.29231.21@snotra> (raw)
In-Reply-To: <1367454443.29231.20@snotra> (from scottwood@freescale.com on Wed May 1 19:27:23 2013)
On 05/01/2013 07:27:23 PM, Scott Wood wrote:
> On 05/01/2013 07:15:53 PM, Marcelo Tosatti wrote:
>> This is not good practice (codepaths should either hold srcu or not
>> hold
>> it, unconditionally).
>
> How is it different from moving the srcu lock into individual cases
> of the switch? I just did it this way to make it easier to add new
> exception types if necessary (e.g. at the time I thought I'd end up
> adding exceptions which lead to instruction emulation, but I ended up
> acquiring the lock further down the path in that case).
>
>> Can you give more details of the issue? (not obvious)
>
> ITLB/DTLB miss call things like gfn_to_memslot() which need the lock
> (but don't grab it themselves -- that seems like the real bad
> practice here...).
Never mind on the parenthetical -- grabbing it themselves wouldn't work
because they return RCU-protected data.
-Scott
WARNING: multiple messages have this Message-ID (diff)
From: Scott Wood <scottwood@freescale.com>
To: Scott Wood <scottwood@freescale.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
Alexander Graf <agraf@suse.de>, <kvm-ppc@vger.kernel.org>,
<kvm@vger.kernel.org>
Subject: Re: [PATCH 1/3] kvm/ppc/booke: Hold srcu lock when calling gfn functions
Date: Wed, 1 May 2013 19:30:04 -0500 [thread overview]
Message-ID: <1367454604.29231.21@snotra> (raw)
In-Reply-To: <1367454443.29231.20@snotra> (from scottwood@freescale.com on Wed May 1 19:27:23 2013)
On 05/01/2013 07:27:23 PM, Scott Wood wrote:
> On 05/01/2013 07:15:53 PM, Marcelo Tosatti wrote:
>> This is not good practice (codepaths should either hold srcu or not
>> hold
>> it, unconditionally).
>
> How is it different from moving the srcu lock into individual cases
> of the switch? I just did it this way to make it easier to add new
> exception types if necessary (e.g. at the time I thought I'd end up
> adding exceptions which lead to instruction emulation, but I ended up
> acquiring the lock further down the path in that case).
>
>> Can you give more details of the issue? (not obvious)
>
> ITLB/DTLB miss call things like gfn_to_memslot() which need the lock
> (but don't grab it themselves -- that seems like the real bad
> practice here...).
Never mind on the parenthetical -- grabbing it themselves wouldn't work
because they return RCU-protected data.
-Scott
next prev parent reply other threads:[~2013-05-02 0:30 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-27 0:53 [PATCH 1/3] kvm/ppc/booke: Hold srcu lock when calling gfn functions Scott Wood
2013-04-27 0:53 ` Scott Wood
2013-04-27 0:53 ` [PATCH 2/3] kvm/ppc: Hold srcu lock when calling kvm_io_bus_read/write Scott Wood
2013-04-27 0:53 ` Scott Wood
2013-05-02 11:22 ` Alexander Graf
2013-05-02 11:22 ` Alexander Graf
2013-04-27 0:53 ` [PATCH 3/3] kvm: Fix obsolete comment about locking for kvm_io_bus_read/write Scott Wood
2013-04-27 0:53 ` Scott Wood
2013-05-01 23:24 ` Alexander Graf
2013-05-01 23:24 ` Alexander Graf
2013-05-02 7:18 ` Gleb Natapov
2013-05-02 7:18 ` Gleb Natapov
2013-05-02 10:53 ` Alexander Graf
2013-05-02 10:53 ` Alexander Graf
2013-05-02 11:00 ` Gleb Natapov
2013-05-02 11:00 ` Gleb Natapov
2013-05-02 11:25 ` Alexander Graf
2013-05-02 11:25 ` Alexander Graf
2013-05-02 0:15 ` [PATCH 1/3] kvm/ppc/booke: Hold srcu lock when calling gfn functions Marcelo Tosatti
2013-05-02 0:15 ` Marcelo Tosatti
2013-05-02 0:27 ` Scott Wood
2013-05-02 0:27 ` Scott Wood
2013-05-02 0:30 ` Scott Wood [this message]
2013-05-02 0:30 ` Scott Wood
2013-05-02 11:20 ` Alexander Graf
2013-05-02 11:20 ` Alexander Graf
2013-05-02 14:37 ` Marcelo Tosatti
2013-05-02 14:37 ` Marcelo Tosatti
2013-05-02 16:47 ` Scott Wood
2013-05-02 16:47 ` Scott Wood
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