linux-kernel - Re: [PATCH v10 2/7] arm64: hyperv: Add Hyper-V hypercall and register access utilities

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Message-ID: <20210514125243.GC30645@C02TD0UTHF1T.local>
Date:   Fri, 14 May 2021 13:52:43 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     will@...nel.org, catalin.marinas@....com,
        lorenzo.pieralisi@....com, sudeep.holla@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-efi@...r.kernel.org,
        arnd@...db.de, wei.liu@...nel.org, ardb@...nel.org,
        daniel.lezcano@...aro.org, kys@...rosoft.com
Subject: Re: [PATCH v10 2/7] arm64: hyperv: Add Hyper-V hypercall and
 register access utilities

On Wed, May 12, 2021 at 10:37:42AM -0700, Michael Kelley wrote:
> hyperv-tlfs.h defines Hyper-V interfaces from the Hyper-V Top Level
> Functional Spec (TLFS), and #includes the architecture-independent
> part of hyperv-tlfs.h in include/asm-generic.  The published TLFS
> is distinctly oriented to x86/x64, so the ARM64-specific
> hyperv-tlfs.h includes information for ARM64 that is not yet formally
> published. The TLFS is available here:
> 
>   docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs
> 
> mshyperv.h defines Linux-specific structures and routines for
> interacting with Hyper-V on ARM64, and #includes the architecture-
> independent part of mshyperv.h in include/asm-generic.
> 
> Use these definitions to provide utility functions to make
> Hyper-V hypercalls and to get and set Hyper-V provided
> registers associated with a virtual processor.
> 
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> Reviewed-by: Sunil Muthuswamy <sunilmut@...rosoft.com>
> ---
>  MAINTAINERS                          |   3 +
>  arch/arm64/Kbuild                    |   1 +
>  arch/arm64/hyperv/Makefile           |   2 +
>  arch/arm64/hyperv/hv_core.c          | 130 +++++++++++++++++++++++++++++++++++
>  arch/arm64/include/asm/hyperv-tlfs.h |  69 +++++++++++++++++++
>  arch/arm64/include/asm/mshyperv.h    |  54 +++++++++++++++
>  6 files changed, 259 insertions(+)
>  create mode 100644 arch/arm64/hyperv/Makefile
>  create mode 100644 arch/arm64/hyperv/hv_core.c
>  create mode 100644 arch/arm64/include/asm/hyperv-tlfs.h
>  create mode 100644 arch/arm64/include/asm/mshyperv.h

> +/*
> + * hv_do_hypercall- Invoke the specified hypercall
> + */
> +u64 hv_do_hypercall(u64 control, void *input, void *output)
> +{
> +	struct arm_smccc_res	res;
> +	u64			input_address;
> +	u64			output_address;
> +
> +	input_address = input ? virt_to_phys(input) : 0;
> +	output_address = output ? virt_to_phys(output) : 0;

I may have asked this before, but are `input` and `output` always linear
map pointers, or can they ever be vmalloc pointers?

Otherwise, this looks fine to me.

Mark.