linux-kernel - Re: [PATCH v3 05/11] kvm: arm64: Remove hyp_adr/ldr_this

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Message-ID: <20200921171503.GB2822@willie-the-truck>
Date:   Mon, 21 Sep 2020 18:15:05 +0100
From:   Will Deacon <will@...nel.org>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Andrew Scull <ascull@...gle.com>
Subject: Re: [PATCH v3 05/11] kvm: arm64: Remove hyp_adr/ldr_this_cpu

On Mon, Sep 21, 2020 at 03:53:20PM +0100, David Brazdil wrote:
> > Cosmetic, but I think it would be cleaner just to define two variants of the
> > macro here:
> > 
> > #if defined(__KVM_NVHE_HYPERVISOR__) || defined(__KVM_VHE_HYPERVISOR__)
> > 	.macro  this_cpu_offset, dst
> > 	mrs     \dst, tpidr_el2
> > 	.endm
> > #else
> > 	.macro  this_cpu_offset, dst
> > alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
> > 	mrs     \dst, tpidr_el1
> > alternative_else
> > 	mrs     \dst, tpidr_el2
> > alternative_endif
> > 	.endm
> > #endif
> 
> Sure.

Ta.

> > (and should we have a shorthand __HYPERVISOR define to avoid the NVHE || VHE
> > logic?)
> 
> Happy to add this but let's agree on the details.
>  * name: just __HYPERVISOR or __KVM_HYPERVISOR__?

Hey, I leave the hard decisions to others!

>  * defined where? I'm wary of defining it in a header file because then sombody
>    will forget to add it and 'ifdef HYP' will be skipped. So I'd put this as
>    another '-D__HYPERVISOR' in the build rules. Do you agree?

Hmm, that's a good point. Leave that part as-is for now then and we can
tackle it separately if it comes up again.

Will