linux-kernel - Re: [PATCH v5 04/17] x86/acrn: Introduce hypercall interfaces

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Date:   Mon, 19 Oct 2020 14:53:29 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     shuo.a.liu@...el.com
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yu Wang <yu1.wang@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Yakui Zhao <yakui.zhao@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Fengwei Yin <fengwei.yin@...el.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Peter Zijlstra <peterz@...radead.org>,
        Segher Boessenkool <segher@...nel.crashing.org>
Subject: Re: [PATCH v5 04/17] x86/acrn: Introduce hypercall interfaces

On Sun, Oct 18, 2020 at 11:18 PM <shuo.a.liu@...el.com> wrote:
>
> From: Shuo Liu <shuo.a.liu@...el.com>
>
> The Service VM communicates with the hypervisor via conventional
> hypercalls. VMCALL instruction is used to make the hypercalls.
>
> ACRN hypercall ABI:
>   * Hypercall number is in R8 register.
>   * Up to 2 parameters are in RDI and RSI registers.
>   * Return value is in RAX register.
>
> Introduce the ACRN hypercall interfaces. Because GCC doesn't support R8
> register as direct register constraints, use supported constraint as
> input with a explicit MOV to R8 in beginning of asm.

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Originally-by: Yakui Zhao <yakui.zhao@...el.com>
> Signed-off-by: Shuo Liu <shuo.a.liu@...el.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Fengwei Yin <fengwei.yin@...el.com>
> Cc: Zhi Wang <zhi.a.wang@...el.com>
> Cc: Zhenyu Wang <zhenyuw@...ux.intel.com>
> Cc: Yu Wang <yu1.wang@...el.com>
> Cc: Reinette Chatre <reinette.chatre@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Arvind Sankar <nivedita@...m.mit.edu>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Segher Boessenkool <segher@...nel.crashing.org>
> ---
>  arch/x86/include/asm/acrn.h | 54 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 54 insertions(+)
>
> diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
> index a2d4aea3a80d..03e420245505 100644
> --- a/arch/x86/include/asm/acrn.h
> +++ b/arch/x86/include/asm/acrn.h
> @@ -14,4 +14,58 @@ void acrn_setup_intr_handler(void (*handler)(void));
>  void acrn_remove_intr_handler(void);
>  bool acrn_is_privileged_vm(void);
>
> +/*
> + * Hypercalls for ACRN
> + *
> + * - VMCALL instruction is used to implement ACRN hypercalls.
> + * - ACRN hypercall ABI:
> + *   - Hypercall number is passed in R8 register.
> + *   - Up to 2 arguments are passed in RDI, RSI.
> + *   - Return value will be placed in RAX.
> + *
> + * Because GCC doesn't support R8 register as direct register constraints, use
> + * supported constraint as input with a explicit MOV to R8 in beginning of asm.
> + */
> +static inline long acrn_hypercall0(unsigned long hcall_id)
> +{
> +       long result;
> +
> +       asm volatile("movl %1, %%r8d\n\t"
> +                    "vmcall\n\t"
> +                    : "=a" (result)
> +                    : "ir" (hcall_id)
> +                    : "r8", "memory");
> +
> +       return result;
> +}
> +
> +static inline long acrn_hypercall1(unsigned long hcall_id,
> +                                  unsigned long param1)
> +{
> +       long result;
> +
> +       asm volatile("movl %1, %%r8d\n\t"
> +                    "vmcall\n\t"
> +                    : "=a" (result)
> +                    : "ir" (hcall_id), "D" (param1)
> +                    : "r8", "memory");
> +
> +       return result;
> +}
> +
> +static inline long acrn_hypercall2(unsigned long hcall_id,
> +                                  unsigned long param1,
> +                                  unsigned long param2)
> +{
> +       long result;
> +
> +       asm volatile("movl %1, %%r8d\n\t"
> +                    "vmcall\n\t"
> +                    : "=a" (result)
> +                    : "ir" (hcall_id), "D" (param1), "S" (param2)
> +                    : "r8", "memory");
> +
> +       return result;
> +}
> +
>  #endif /* _ASM_X86_ACRN_H */
> --
> 2.28.0
>


-- 
Thanks,
~Nick Desaulniers