From: Mark Brown <broonie@kernel•org>
To: Will Deacon <will@kernel•org>
Cc: Mark Rutland <mark.rutland@arm•com>,
Catalin Marinas <catalin.marinas@arm•com>,
linux-arm-kernel@lists•infradead.org,
Suzuki K Poulose <suzuki.poulose@arm•com>
Subject: Re: [PATCH v2 1/2] arm64: Add initial support for E0PD
Date: Fri, 11 Oct 2019 14:46:55 +0100 [thread overview]
Message-ID: <20191011134655.GI4741@sirena.org.uk> (raw)
In-Reply-To: <20191011114013.ovvs36rrolkn2hzv@willie-the-truck>
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On Fri, Oct 11, 2019 at 12:40:13PM +0100, Will Deacon wrote:
> On Fri, Oct 11, 2019 at 12:17:15PM +0100, Mark Brown wrote:
> > It does - the main motivation for doing it as a local feature was
> > to avoid the regression with systems with late CPUs that lack the
> > capability which Will was concerned about but I'm not sure how
> > realistic such systems actually are.
> I think we need to handle the case where not all CPUs support ExPD :(
> It's not like E0PD is something critical like support for a particular page
> size, so I think it's a tough sell for SoC integrators to ensure that it's
> matched up.
That's fine, we handle them by falling back to KPTI if we detect
any non-E0PD CPUs. The only difference in the end result between
doing this by making it a system wide capability and doing it as
a weak local capability is what happens if the first CPU that
appears without E0PD is a late CPU then instead of accepting the
CPU and enabling KPTI we will reject the CPU.
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next prev parent reply other threads:[~2019-10-11 13:47 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 18:31 [PATCH v2 0/2] arm64: E0PD support Mark Brown
2019-08-14 18:31 ` [PATCH v2 1/2] arm64: Add initial support for E0PD Mark Brown
2019-10-10 16:13 ` Mark Rutland
2019-10-11 11:17 ` Mark Brown
2019-10-11 11:40 ` Will Deacon
2019-10-11 12:57 ` Mark Rutland
2019-10-11 12:58 ` Catalin Marinas
2019-10-11 13:46 ` Mark Brown [this message]
2019-08-14 18:31 ` [PATCH v2 2/2] arm64: Don't use KPTI where we have E0PD Mark Brown
2019-08-15 16:35 ` Will Deacon
2019-08-15 18:00 ` Mark Brown
2019-08-16 11:31 ` Mark Brown
2019-08-16 10:24 ` Catalin Marinas
2019-08-16 12:10 ` Mark Brown
2019-09-24 9:13 ` Suzuki K Poulose
2019-10-09 17:52 ` Mark Brown
2019-10-10 10:24 ` Suzuki K Poulose
2019-10-10 16:04 ` Mark Brown
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