Re: [PATCH v6 4/4] x86/acrn: Add hypercall for ACRN guest

[Borislav Petkov]

On Tue, Apr 30, 2019 at 11:45:26AM +0800, Zhao Yakui wrote:
> When the ACRN hypervisor is detected, the hypercall is needed so that the
> ACRN guest can query/config some settings. For example: it can be used
> to query the resources in hypervisor and manage the CPU/memory/device/
> interrupt for guest operating system.
> 
> Add the hypercall so that the ACRN guest can communicate with the
> low-level ACRN hypervisor. On x86 it is implemented with the VMCALL
> instruction.
> 
> Co-developed-by: Jason Chen CJ <jason.cj.chen@xxxxxxxxx>
> Signed-off-by: Jason Chen CJ <jason.cj.chen@xxxxxxxxx>
> Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
> V1->V2: Refine the comments for the function of acrn_hypercall0/1/2
> v2->v3: Use the "vmcall" mnemonic to replace hard-code byte definition
> v4->v5: Use _ASM_X86_ACRN_HYPERCALL_H instead of _ASM_X86_ACRNHYPERCALL_H.
>         Use the "VMCALL" mnemonic in comment/commit log.
>         Uppercase r8/rdi/rsi/rax for hypercall parameter register in comment.
> v5->v6: Remove explicit local register variable for inline assembly
> ---
>  arch/x86/include/asm/acrn_hypercall.h | 84 +++++++++++++++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
>  create mode 100644 arch/x86/include/asm/acrn_hypercall.h
> 
> diff --git a/arch/x86/include/asm/acrn_hypercall.h b/arch/x86/include/asm/acrn_hypercall.h
> new file mode 100644
> index 0000000..5cb438e
> --- /dev/null
> +++ b/arch/x86/include/asm/acrn_hypercall.h

Questions:

* why isn't this in acrn.h and needs to be a separate header?

* why aren't those functions used anywhere?

-- 
Regards/Gruss,
    Boris.

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