Re: [Xen-devel] [PATCH v4 3/7] x86/hyperv: provide Hyper-V hypercall functions

[Jan Beulich <jbeulich@suse.com>]

On 22.01.2020 21:23, Wei Liu wrote:
> --- /dev/null
> +++ b/xen/include/asm-x86/guest/hyperv-hcall.h
> @@ -0,0 +1,98 @@
> +/******************************************************************************
> + * asm-x86/guest/hyperv-hcall.h
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms and conditions of the GNU General Public
> + * License, version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public
> + * License along with this program; If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Copyright (c) 2019 Microsoft.
> + */
> +
> +#ifndef __X86_HYPERV_HCALL_H__
> +#define __X86_HYPERV_HCALL_H__
> +
> +#include <xen/lib.h>
> +#include <xen/types.h>
> +
> +#include <asm/asm_defns.h>
> +#include <asm/fixmap.h>
> +#include <asm/guest/hyperv-tlfs.h>
> +#include <asm/page.h>
> +
> +static inline uint64_t hv_do_hypercall(uint64_t control, paddr_t input_addr,
> +                                       paddr_t output_addr)
> +{
> +    uint64_t status;
> +    register unsigned long r8 asm("r8") = output_addr;
> +
> +    asm volatile ("INDIRECT_CALL %P[hcall_page]"
> +                  : "=a" (status), "+c" (control),
> +                    "+d" (input_addr) ASM_CALL_CONSTRAINT
> +                  : "r" (r8),
> +                    [hcall_page] "p" (fix_x_to_virt(FIX_X_HYPERV_HCALL))
> +                  : "memory");
> +
> +    return status;
> +}
> +
> +static inline uint64_t hv_do_fast_hypercall(uint16_t code,
> +                                            uint64_t input1, uint64_t input2)
> +{
> +    uint64_t status;
> +    uint64_t control = code | HV_HYPERCALL_FAST_BIT;
> +    register unsigned long r8 asm("r8") = input2;
> +
> +    asm volatile ("INDIRECT_CALL %P[hcall_page]"
> +                  : "=a" (status), "+c" (control),
> +                    "+d" (input1) ASM_CALL_CONSTRAINT
> +                  : "r" (r8),
> +                    [hcall_page] "p" (fix_x_to_virt(FIX_X_HYPERV_HCALL))
> +                  :);

This comes through as a smiley in my mail viewer, because of the
missing blanks immediately inside the outermost parentheses.

> +
> +    return status;
> +}
> +
> +static inline uint64_t hv_do_rep_hypercall(uint16_t code, uint16_t rep_count,
> +                                           uint16_t varhead_size,
> +                                           paddr_t input, paddr_t output)
> +{
> +    uint64_t control = code;
> +    uint64_t status;
> +    uint16_t rep_comp;
> +
> +    control |= (uint64_t)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
> +    control |= (uint64_t)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;

What about the upper bit(s) spilling into the next field? Perhaps
better use MASK_INSR() here too?

Also, this leaves the START field zero, which makes me think you
mean ...

> +    do {
> +        status = hv_do_hypercall(control, input, output);
> +        if ( (status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS )
> +            break;
> +
> +        rep_comp = MASK_EXTR(status, HV_HYPERCALL_REP_COMP_MASK);
> +
> +        control &= ~HV_HYPERCALL_REP_START_MASK;
> +        control |= MASK_INSR(rep_comp, HV_HYPERCALL_REP_COMP_MASK);

... REP_START_MASK here.

Jan

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