From: Marc Zyngier <marc.zyngier@arm.com>
To: Will Deacon <will@kernel.org>,
Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
Marc Zyngier <maz@kernel.org>,
guohanjun@huawei.com, James Morse <james.morse@arm.com>,
huawei.libin@huawei.com,
Catalin Marinas <catalin.marinas@arm.com>,
liwei391@huawei.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear
Date: Thu, 1 Aug 2019 11:51:33 +0100 [thread overview]
Message-ID: <a7aaf75d-af41-e162-8b78-84342be36907@arm.com> (raw)
In-Reply-To: <20190801104119.quzlr5artm4s2sbc@willie-the-truck>
On 01/08/2019 11:41, Will Deacon wrote:
> On Tue, Jul 30, 2019 at 03:20:45PM +0100, Julien Thierry wrote:
>> From: Marc Zyngier <marc.zyngier@arm.com>
>>
>> The GICv3 architecture specification is incredibly misleading when it
>> comes to PMR and the requirement for a DSB. It turns out that this DSB
>> is only required if the CPU interface sends an Upstream Control
>> message to the redistributor in order to update the RD's view of PMR.
>>
>> This message is only sent when ICC_CTLR_EL1.PMHE is set, which isn't
>> the case in Linux. It can still be set from EL3, so some special care
>> is required. But the upshot is that in the (hopefuly large) majority
>> of the cases, we can drop the DSB altogether.
>>
>> This requires yet another capability and some more runtime patching.
>
> Hmm, does this actually require explicit runtime patching, or can we make
> things a bit simpler with a static key?
The hunk in entry.S is the blocker, AFAICS. Do we have a way to express
static keys in asm?
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2019-08-01 10:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 14:20 [PATCH] arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear Julien Thierry
2019-08-01 10:41 ` Will Deacon
2019-08-01 10:51 ` Marc Zyngier [this message]
2019-08-01 10:56 ` Julien Thierry
2019-08-01 11:07 ` Marc Zyngier
2019-08-01 11:13 ` Will Deacon
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