Re: [Xen-devel] [PATCH v5 10/12] x86/hyperv: provide percpu hypercall input page

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Wei
> Liu
> Sent: 29 January 2020 20:21
> To: Xen Development List <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Wei Liu <liuwe@xxxxxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Durrant, Paul <pdurrant@xxxxxxxxxxxx>;
> Michael Kelley <mikelley@xxxxxxxxxxxxx>; Roger Pau Monné
> <roger.pau@xxxxxxxxxx>
> Subject: [Xen-devel] [PATCH v5 10/12] x86/hyperv: provide percpu hypercall
> input page
> 
> Hyper-V's input / output argument must be 8 bytes aligned an not cross
> page boundary. One way to satisfy those requirements is to use percpu
> page.
> 
> For the foreseeable future we only need to provide input for TLB
> and APIC hypercalls, so skip setting up an output page.
> 
> We will also need to provide an ap_setup hook for secondary cpus to
> setup its own input page.
> 
> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>

Reviewed-by: Paul Durrant <pdurrant@xxxxxxxxxx>

> ---
> v5:
> 1. Adjust to new ap_setup
> 2. Change variable name to hv_pcpu_input_page
> 
> v4:
> 1. Change wording in commit message
> 2. Prevent leak
> 3. Introduce a private header
> 
> v3:
> 1. Use xenheap page instead
> 2. Drop page tracking structure
> 3. Drop Paul's review tag
> ---
>  xen/arch/x86/guest/hyperv/hyperv.c  | 31 +++++++++++++++++++++++++++++
>  xen/arch/x86/guest/hyperv/private.h | 29 +++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+)
>  create mode 100644 xen/arch/x86/guest/hyperv/private.h
> 
> diff --git a/xen/arch/x86/guest/hyperv/hyperv.c
> b/xen/arch/x86/guest/hyperv/hyperv.c
> index 4387b6541e..f0facccbad 100644
> --- a/xen/arch/x86/guest/hyperv/hyperv.c
> +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> @@ -27,7 +27,10 @@
>  #include <asm/guest/hyperv-tlfs.h>
>  #include <asm/processor.h>
> 
> +#include "private.h"
> +
>  struct ms_hyperv_info __read_mostly ms_hyperv;
> +DEFINE_PER_CPU_READ_MOSTLY(void *, hv_pcpu_input_page);
> 
>  static uint64_t generate_guest_id(void)
>  {
> @@ -127,14 +130,42 @@ static void __init setup_hypercall_page(void)
>      }
>  }
> 
> +static int setup_hypercall_pcpu_arg(void)
> +{
> +    void *mapping;
> +
> +    if ( this_cpu(hv_pcpu_input_page) )
> +        return 0;
> +
> +    mapping = alloc_xenheap_page();
> +    if ( !mapping )
> +    {
> +        printk("Failed to allocate hypercall input page for CPU%u\n",
> +               smp_processor_id());
> +        return -ENOMEM;
> +    }
> +
> +    this_cpu(hv_pcpu_input_page) = mapping;
> +
> +    return 0;
> +}
> +
>  static void __init setup(void)
>  {
>      setup_hypercall_page();
> +    if ( setup_hypercall_pcpu_arg() )
> +        panic("Hypercall percpu arg setup failed\n");
> +}
> +
> +static int ap_setup(void)
> +{
> +    return setup_hypercall_pcpu_arg();
>  }
> 
>  static const struct hypervisor_ops ops = {
>      .name = "Hyper-V",
>      .setup = setup,
> +    .ap_setup = ap_setup,
>  };
> 
>  static void __maybe_unused build_assertions(void)
> diff --git a/xen/arch/x86/guest/hyperv/private.h
> b/xen/arch/x86/guest/hyperv/private.h
> new file mode 100644
> index 0000000000..a339274985
> --- /dev/null
> +++ b/xen/arch/x86/guest/hyperv/private.h
> @@ -0,0 +1,29 @@
> +/************************************************************************
> ******
> + * arch/x86/guest/hyperv/private.h
> + *
> + * Definitions / declarations only useful to Hyper-V code.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * 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) 2020 Microsoft.
> + */
> +
> +#ifndef __XEN_HYPERV_PRIVIATE_H__
> +#define __XEN_HYPERV_PRIVIATE_H__
> +
> +#include <xen/percpu.h>
> +
> +DECLARE_PER_CPU(void *, hv_pcpu_input_page);
> +
> +#endif /* __XEN_HYPERV_PRIVIATE_H__  */
> --
> 2.20.1
> 
> 
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