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From: Marc Zyngier <maz@kernel.org>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: mark.rutland@arm.com, saiprakash.ranjan@codeaurora.org,
	kernel-team@android.com, anshuman.khandual@arm.com,
	catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
	dianders@chromium.org, will@kernel.org,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 8/8] arm64: cpufeature: Add an overview comment for the cpufeature framework
Date: Thu, 16 Apr 2020 16:26:05 +0100	[thread overview]
Message-ID: <96438d59a2bc05871ef68fca475fabf5@kernel.org> (raw)
In-Reply-To: <96dd797d-ccfe-c867-0a70-65eccacde3cd@arm.com>

On 2020-04-16 15:59, Suzuki K Poulose wrote:

Hi Suzuki,

[...]

> As you mentioned in the other response we could add information about
> the guest view, something like :
> 
>       - KVM exposes the sanitised value of the feature registers to the
> 	guests and is not affected by the FTR_VISIBLE. However,
> 	depending on the individual feature support in the hypervisor,
> 	some of the fields may be capped/limited.

Although in most cases, what KVM exposes is indeed a strict subset of
the host's features, there is a few corner cases where we expose 
features
that do not necessarily exist on the host. For example ARMv8.5-GTG and
ARMv8.4-TTL get exposed by the NV patches even if they don't exist on 
the
host, as KVM will actually emulate them.

Not a big deal, but I just wanted to outline that it isn't as clear-cut 
as
it may seem...

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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  reply	other threads:[~2020-04-16 15:28 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-14 21:31 [PATCH 0/8] Relax sanity checking for mismatched AArch32 EL1 Will Deacon
2020-04-14 21:31 ` [PATCH 1/8] arm64: cpufeature: Relax check for IESB support Will Deacon
2020-04-15 10:02   ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 2/8] arm64: cpufeature: Spell out register fields for ID_ISAR4 and ID_PFR1 Will Deacon
2020-04-15 10:09   ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 3/8] arm64: cpufeature: Add CPU capability for AArch32 EL1 support Will Deacon
2020-04-15  8:55   ` Marc Zyngier
2020-04-15 17:00     ` Will Deacon
2020-04-15 10:13   ` Suzuki K Poulose
2020-04-15 10:14     ` Will Deacon
2020-04-15 13:15       ` Suzuki K Poulose
2020-04-15 13:22         ` Marc Zyngier
2020-04-17  9:44           ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 4/8] arm64: cpufeature: Remove redundant call to id_aa64pfr0_32bit_el0() Will Deacon
2020-04-15 10:25   ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 5/8] arm64: cpufeature: Factor out checking of AArch32 features Will Deacon
2020-04-15 10:36   ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 6/8] arm64: cpufeature: Relax AArch32 system checks if EL1 is 64-bit only Will Deacon
2020-04-15 10:43   ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 7/8] arm64: cpufeature: Relax checks for AArch32 support at EL[0-2] Will Deacon
2020-04-15 10:50   ` Suzuki K Poulose
2020-04-15 10:58     ` Will Deacon
2020-04-15 11:37       ` Suzuki K Poulose
2020-04-15 12:29         ` Will Deacon
2020-04-17  9:37           ` Suzuki K Poulose
2020-04-14 21:31 ` [PATCH 8/8] arm64: cpufeature: Add an overview comment for the cpufeature framework Will Deacon
2020-04-16 11:58   ` Will Deacon
2020-04-16 14:59   ` Suzuki K Poulose
2020-04-16 15:26     ` Marc Zyngier [this message]
2020-04-16 18:12     ` Will Deacon
2020-04-16  8:39 ` [PATCH 0/8] Relax sanity checking for mismatched AArch32 EL1 Sai Prakash Ranjan
2020-04-16 10:26   ` Sai Prakash Ranjan

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