linux-kernel - Re: [PATCH v5 06/16] x86/hyperv: allocate output arg pages if required

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Message-ID: <CA+CK2bDOhzx1_TcWQp2zFUb5+59ayFby=ZSoNyApNEQ0FRJUFA@mail.gmail.com>
Date:   Wed, 20 Jan 2021 14:44:34 -0500
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Wei Liu <wei.liu@...nel.org>
Cc:     Linux on Hyper-V List <linux-hyperv@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
        Lillian Grassin-Drake <ligrassi@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v5 06/16] x86/hyperv: allocate output arg pages if required

On Wed, Jan 20, 2021 at 7:01 AM Wei Liu <wei.liu@...nel.org> wrote:
>
> When Linux runs as the root partition, it will need to make hypercalls
> which return data from the hypervisor.
>
> Allocate pages for storing results when Linux runs as the root
> partition.
>
> Signed-off-by: Lillian Grassin-Drake <ligrassi@...rosoft.com>
> Co-Developed-by: Lillian Grassin-Drake <ligrassi@...rosoft.com>
> Signed-off-by: Wei Liu <wei.liu@...nel.org>

Reviewed-by: Pavel Tatashin <pasha.tatashin@...een.com>

The new warnings reported by the robot are the same as for the input argument.

Pasha

> ---
> v3: Fix hv_cpu_die to use free_pages.
> v2: Address Vitaly's comments
> ---
>  arch/x86/hyperv/hv_init.c       | 35 ++++++++++++++++++++++++++++-----
>  arch/x86/include/asm/mshyperv.h |  1 +
>  2 files changed, 31 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index e04d90af4c27..6f4cb40e53fe 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -41,6 +41,9 @@ EXPORT_SYMBOL_GPL(hv_vp_assist_page);
>  void  __percpu **hyperv_pcpu_input_arg;
>  EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
>
> +void  __percpu **hyperv_pcpu_output_arg;
> +EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
> +
>  u32 hv_max_vp_index;
>  EXPORT_SYMBOL_GPL(hv_max_vp_index);
>
> @@ -73,12 +76,19 @@ static int hv_cpu_init(unsigned int cpu)
>         void **input_arg;
>         struct page *pg;
>
> -       input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
>         /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> -       pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
> +       pg = alloc_pages(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, hv_root_partition ? 1 : 0);
>         if (unlikely(!pg))
>                 return -ENOMEM;
> +
> +       input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
>         *input_arg = page_address(pg);
> +       if (hv_root_partition) {
> +               void **output_arg;
> +
> +               output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> +               *output_arg = page_address(pg + 1);
> +       }
>
>         hv_get_vp_index(msr_vp_index);
>
> @@ -205,14 +215,23 @@ static int hv_cpu_die(unsigned int cpu)
>         unsigned int new_cpu;
>         unsigned long flags;
>         void **input_arg;
> -       void *input_pg = NULL;
> +       void *pg;
>
>         local_irq_save(flags);
>         input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> -       input_pg = *input_arg;
> +       pg = *input_arg;
>         *input_arg = NULL;
> +
> +       if (hv_root_partition) {
> +               void **output_arg;
> +
> +               output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> +               *output_arg = NULL;
> +       }
> +
>         local_irq_restore(flags);
> -       free_page((unsigned long)input_pg);
> +
> +       free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);
>
>         if (hv_vp_assist_page && hv_vp_assist_page[cpu])
>                 wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
> @@ -346,6 +365,12 @@ void __init hyperv_init(void)
>
>         BUG_ON(hyperv_pcpu_input_arg == NULL);
>
> +       /* Allocate the per-CPU state for output arg for root */
> +       if (hv_root_partition) {
> +               hyperv_pcpu_output_arg = alloc_percpu(void *);
> +               BUG_ON(hyperv_pcpu_output_arg == NULL);
> +       }
> +
>         /* Allocate percpu VP index */
>         hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
>                                     GFP_KERNEL);
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index ac2b0d110f03..62d9390f1ddf 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -76,6 +76,7 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}
>  #if IS_ENABLED(CONFIG_HYPERV)
>  extern void *hv_hypercall_pg;
>  extern void  __percpu  **hyperv_pcpu_input_arg;
> +extern void  __percpu  **hyperv_pcpu_output_arg;
>
>  static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
>  {
> --
> 2.20.1
>