linux-kernel - RE: [PATCH v2 6/6] Drivers: hv: vmbus: Support TDX guests

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Message-ID: <SA1PR21MB1335D873764C7440AE68E460BFE29@SA1PR21MB1335.namprd21.prod.outlook.com>
Date:   Mon, 12 Dec 2022 19:18:52 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 6/6] Drivers: hv: vmbus: Support TDX guests

> From: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> Sent: Monday, December 12, 2022 9:02 AM
> > [...]
> > @@ -225,6 +275,10 @@ void hv_synic_enable_regs(unsigned int cpu)
> >  	} else {
> >  		simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> >  			>> HV_HYP_PAGE_SHIFT;
> > +
> > +		if (hv_isolation_type_tdx())
> > +			simp.base_simp_gpa |= ms_hyperv.shared_gpa_boundary
> > +				>> HV_HYP_PAGE_SHIFT;
> 
> Since we're using cc_mkdec() in hv_do_hypercall() to set the SHARED bit,
> perhaps the same could be done here to simplify the code and avoid the
> explicit call to hv_isolation_type_tdx():

Good idea! Will do.

> 		simp.base_simp_gpa =
> cc_mkdec(virt_to_phys(hv_cpu->synic_message))
> 			>> HV_HYP_PAGE_SHIFT;
> 
> cc_mkdec() does nothing in a normal VM, and vTOM VMs are already
> special-cased.

This should work for C-bit SNP as well (clearing cc_mask from the GPA
doesn't really change the GPA since the GPA doesn't have the bit in the
first place).

> >  	hv_set_register(HV_REGISTER_SIMP, simp.as_uint64);
> > @@ -243,6 +297,10 @@ void hv_synic_enable_regs(unsigned int cpu)
> >  	} else {
> >  		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> >  			>> HV_HYP_PAGE_SHIFT;
> > +
> > +		if (hv_isolation_type_tdx())
> > +			siefp.base_siefp_gpa |= ms_hyperv.shared_gpa_boundary
> > +				>> HV_HYP_PAGE_SHIFT;
> 
> Same here.

Will do.