linux-kernel - Re: [PATCH v2 2/5] x86: hv: hv_init.c: Add functions to allocate/deallocate page for Hyper-V

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Date:   Wed, 12 Jun 2019 12:36:47 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maya Nakamura <m.maya.nakamura@...il.com>
Cc:     x86@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org
Subject: Re: [PATCH v2 2/5] x86: hv: hv_init.c: Add functions to allocate/deallocate page for Hyper-V

Maya Nakamura <m.maya.nakamura@...il.com> writes:

> Introduce two new functions, hv_alloc_hyperv_page() and
> hv_free_hyperv_page(), to allocate/deallocate memory with the size and
> alignment that Hyper-V expects as a page. Although currently they are
> not used, they are ready to be used to allocate/deallocate memory on x86
> when their ARM64 counterparts are implemented, keeping symmetry between
> architectures with potentially different guest page sizes.
>
> Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> ---
>  arch/x86/hyperv/hv_init.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index e4ba467a9fc6..84baf0e9a2d4 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -98,6 +98,20 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
>  u32 hv_max_vp_index;
>  EXPORT_SYMBOL_GPL(hv_max_vp_index);
>  
> +void *hv_alloc_hyperv_page(void)
> +{
> +	BUILD_BUG_ON(!(PAGE_SIZE == HV_HYP_PAGE_SIZE));

(nit)

PAGE_SIZE != HV_HYP_PAGE_SIZE ?

> +
> +	return (void *)__get_free_page(GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
> +
> +void hv_free_hyperv_page(unsigned long addr)
> +{
> +	free_page(addr);
> +}
> +EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
> +
>  static int hv_cpu_init(unsigned int cpu)
>  {
>  	u64 msr_vp_index;

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly