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:

quoted

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@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.cs.columbia.edu
Cc: linux-kernel@vger.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

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