linux-kernel - Re: [PATCH V3 03/13] x86/HV: Add new hvcall guest address host visibility support

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Date:   Mon, 9 Aug 2021 15:12:33 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Tianyu Lan <ltykernel@...il.com>, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
        jgross@...e.com, sstabellini@...nel.org, joro@...tes.org,
        will@...nel.org, davem@...emloft.net, kuba@...nel.org,
        jejb@...ux.ibm.com, martin.petersen@...cle.com, arnd@...db.de,
        hch@....de, m.szyprowski@...sung.com, robin.murphy@....com,
        thomas.lendacky@....com, brijesh.singh@....com, ardb@...nel.org,
        Tianyu.Lan@...rosoft.com, pgonda@...gle.com,
        martin.b.radev@...il.com, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, rppt@...nel.org,
        sfr@...b.auug.org.au, saravanand@...com,
        krish.sadhukhan@...cle.com, aneesh.kumar@...ux.ibm.com,
        xen-devel@...ts.xenproject.org, rientjes@...gle.com,
        hannes@...xchg.org, tj@...nel.org, michael.h.kelley@...rosoft.com
Cc:     iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, netdev@...r.kernel.org,
        vkuznets@...hat.com, parri.andrea@...il.com
Subject: Re: [PATCH V3 03/13] x86/HV: Add new hvcall guest address host
 visibility support

On 8/9/21 10:56 AM, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> 
> Add new hvcall guest address host visibility support to mark
> memory visible to host. Call it inside set_memory_decrypted
> /encrypted(). Add HYPERVISOR feature check in the
> hv_is_isolation_supported() to optimize in non-virtualization
> environment.

>From an x86/mm perspective:

Acked-by: Dave Hansen <dave.hansen@...el.com>

A tiny nit:

> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 0bb4d9ca7a55..b3683083208a 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -607,6 +607,12 @@ EXPORT_SYMBOL_GPL(hv_get_isolation_type);
>  
>  bool hv_is_isolation_supported(void)
>  {
> +	if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
> +		return 0;
> +
> +	if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
> +		return 0;
> +
>  	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
>  }
This might be worthwhile to move to a header.  That ensures that
hv_is_isolation_supported() use can avoid even a function call.  But, I
see this is used in modules and its use here is also in a slow path, so
it's not a big deal