linux-kernel - Re: [PATCHv3.1 2/32] x86/coco: Explicitly declare type of confidential computing platform

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Date:   Mon, 21 Feb 2022 13:52:58 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com,
        dave.hansen@...el.com, david@...hat.com, hpa@...or.com,
        jgross@...e.com, jmattson@...gle.com, joro@...tes.org,
        jpoimboe@...hat.com, kirill.shutemov@...ux.intel.com,
        knsathya@...nel.org, linux-kernel@...r.kernel.org, luto@...nel.org,
        mingo@...hat.com, pbonzini@...hat.com, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, sdeep@...are.com,
        seanjc@...gle.com, tglx@...utronix.de, tony.luck@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org,
        linux-hyperv@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [PATCHv3.1 2/32] x86/coco: Explicitly declare type of
 confidential computing platform

On Mon, Feb 21, 2022 at 12:07:15PM +0100, Borislav Petkov wrote:
> On Sat, Feb 19, 2022 at 03:13:04AM +0300, Kirill A. Shutemov wrote:
[...]
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 5a99f993e639..d77cf3a31f07 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -33,6 +33,7 @@
> >  #include <asm/nmi.h>
> >  #include <clocksource/hyperv_timer.h>
> >  #include <asm/numa.h>
> > +#include <asm/coco.h>
> >  
> >  /* Is Linux running as the root partition? */
> >  bool hv_root_partition;
> > @@ -344,6 +345,8 @@ static void __init ms_hyperv_init_platform(void)
> >  		 */
> >  		swiotlb_force = SWIOTLB_FORCE;
> >  #endif
> > +		if (hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE)
> > +			cc_init(CC_VENDOR_HYPERV);
> 
> Isn't that supposed to test HV_ISOLATION_TYPE_SNP instead?
> 
> I mean, I have no clue what HV_ISOLATION_TYPE_VBS is. It is not used
> anywhere in the tree either.
> 
> a6c76bb08dc7 ("x86/hyperv: Load/save the Isolation Configuration leaf")
> calls it "'VBS' (software-based isolation)" - whatever that means - so
> I'm not sure that is going to need the cc-facilities.
> 

Hi Boris and Kirill, I only see VBS mentioned here so I don't have much
context, but VBS likely means virtualization-based security. There is a
public document for it.

https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-vbs

Whether it needs a new isolation type or not, I am not sure. Perhaps
Tianyu can provide more context.

Thanks,
Wei.