linux-kernel - Re: [PATCH V3] arm64/cpufeature: Validate hypervisor capabilities during CPU hotplug

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Message-ID: <e2ccbfdd-85ee-f01c-ce02-462d1a76c273@arm.com>
Date:   Thu, 21 May 2020 06:18:09 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH V3] arm64/cpufeature: Validate hypervisor capabilities
 during CPU hotplug



On 05/20/2020 11:24 PM, Will Deacon wrote:
> On Tue, 12 May 2020 07:27:27 +0530, Anshuman Khandual wrote:
>> This validates hypervisor capabilities like VMID width, IPA range for any
>> hot plug CPU against system finalized values. KVM's view of the IPA space
>> is used while allowing a given CPU to come up. While here, it factors out
>> get_vmid_bits() for general use.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Marc Zyngier <maz@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: James Morse <james.morse@....com>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: kvmarm@...ts.cs.columbia.edu
>> Cc: linux-kernel@...r.kernel.org
> 
> Applied to arm64 (for-next/cpufeature), thanks!
> 
> [1/1] arm64/cpufeature: Validate hypervisor capabilities during CPU hotplug
>       https://git.kernel.org/arm64/c/c73433fc630c
> 
> But please note that I made some changes to verify_hyp_capabilities() so
> that it's (a) static and (b) uses IS_ENABLED to avoid the dummy function
> definition. I also extended the IS_ENABLED_check so that it doesn't
> conflict with the KVM kconfig changes from Fuad. Please shout if you think
> I'm still missing something.

Normally I would have expected get_kvm_ipa_limit() to be unavailable without
CONFIG_KVM_ARM_HOST, causing a build failure. But it does compile correctly.
Probably the compiler does not really look for get_kvm_ipa_limit() definition
after an early check and bailout on !IS_ENABLED(CONFIG_KVM_ARM_HOST).

Nonetheless, changes looks good. Thank you.

- Anshuman