netdev - RE: [PATCH 05/12] x86/hyperv: Change vTOM handling to use standard coco mechanisms

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Message-ID: <BYAPR21MB168867D803CE3A463553BA88D7389@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Thu, 3 Nov 2022 14:12:22 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Tianyu Lan <ltykernel@...il.com>, "hpa@...or.com" <hpa@...or.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
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        Dexuan Cui <decui@...rosoft.com>,
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        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
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        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
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        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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Subject: RE: [PATCH 05/12] x86/hyperv: Change vTOM handling to use standard
 coco mechanisms

From: Tianyu Lan <ltykernel@...il.com> Sent: Thursday, November 3, 2022 7:01 AM
> 
> On 10/21/2022 1:57 AM, Michael Kelley wrote:
> > +
> > +void __init hv_vtom_init(void)
> > +{
> > +	cc_set_vendor(CC_VENDOR_HYPERV);
> > +	cc_set_mask(ms_hyperv.shared_gpa_boundary);
> > +	physical_mask &= ms_hyperv.shared_gpa_boundary - 1;
> 
> 
> hv_vtom_init() also works for VBS case. VBS doesn't have vTOM support
> and so shared_gpa_boundary should not be applied for VBS. Here seems to
> assume ms_hyperv.shared_gpa_boundary to 0 for VBS, right?

Yes, that is correct.  In fact, you'll notice that this patch slightly changes
the code in ms_hyperv_init_platform() so that shared_gpa_boundary is
set only when it is known to be valid; otherwise it is left as zero.  This
change is specifically so that shared_gpa_boundary is zero for the VBS
case.

Michael