linux-kernel - Re: [PATCH v2 1/5] x86: hv: hyperv-tlfs.h: Create and use Hyper-V page definitions

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Date:   Wed, 12 Jun 2019 12:36:01 +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 1/5] x86: hv: hyperv-tlfs.h: Create and use Hyper-V page definitions

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

> Define HV_HYP_PAGE_SHIFT, HV_HYP_PAGE_SIZE, and HV_HYP_PAGE_MASK because
> the Linux guest page size and hypervisor page size concepts are
> different, even though they happen to be the same value on x86.
>
> Also, replace PAGE_SIZE with HV_HYP_PAGE_SIZE.
>
> Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> ---
>  arch/x86/include/asm/hyperv-tlfs.h | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index cdf44aa9a501..44bd68aefd00 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -12,6 +12,16 @@
>  #include <linux/types.h>
>  #include <asm/page.h>
>  
> +/*
> + * While not explicitly listed in the TLFS, Hyper-V always runs with a page size
> + * of 4096. These definitions are used when communicating with Hyper-V using
> + * guest physical pages and guest physical page addresses, since the guest page
> + * size may not be 4096 on all architectures.
> + */
> +#define HV_HYP_PAGE_SHIFT	12
> +#define HV_HYP_PAGE_SIZE	BIT(HV_HYP_PAGE_SHIFT)
> +#define HV_HYP_PAGE_MASK	(~(HV_HYP_PAGE_SIZE - 1))
> +
>  /*
>   * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
>   * is set by CPUID(HvCpuIdFunctionVersionAndFeatures).
> @@ -841,7 +851,7 @@ union hv_gpa_page_range {
>   * count is equal with how many entries of union hv_gpa_page_range can
>   * be populated into the input parameter page.
>   */
> -#define HV_MAX_FLUSH_REP_COUNT ((PAGE_SIZE - 2 * sizeof(u64)) /	\
> +#define HV_MAX_FLUSH_REP_COUNT ((HV_HYP_PAGE_SIZE - 2 * sizeof(u64)) /	\
>  				sizeof(union hv_gpa_page_range))
>  
>  struct hv_guest_mapping_flush_list {

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

-- 
Vitaly