From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "hpa@zytor.com" <hpa@zytor.com>,
KY Srinivasan <kys@microsoft.com>,
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Subject: RE: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms
Date: Wed, 23 Nov 2022 00:59:00 +0000 [thread overview]
Message-ID: <BYAPR21MB16886FF8B35F51964A515CD5D70C9@BYAPR21MB1688.namprd21.prod.outlook.com> (raw)
In-Reply-To: <Y31Kqacbp9R5A1PF@zn.tnic>
From: Borislav Petkov <bp@alien8.de> Sent: Tuesday, November 22, 2022 2:18 PM
>
> On Tue, Nov 22, 2022 at 06:22:46PM +0000, Michael Kelley (LINUX) wrote:
> > I think the core problem here is the naming and meaning of
> > CC_VENDOR_HYPERV. The name was created originally when the
> > Hyper-V vTOM handling code was a lot of special cases. With the
> > changes in this patch series that make the vTOM functionality more
> > mainstream, the name would be better as CC_VENDOR_AMD_VTOM.
>
> No, if CC_VENDOR_HYPERV means different things depending on what kind of
> guests you're doing, then you should not use a CC_VENDOR at all.
Agreed. My proposal is to drop CC_VENDOR_HYPERV entirely.
Replace it with CC_VENDOR_AMD_VTOM (or something like that) that
is set *only* by Linux guests that are running on AMD SEV-SNP processors
and using the vTOM scheme instead of the AMD C-bit scheme.
>
> > vTOM is part of the AMD SEV-SNP spec, and it's a different way of
> > doing the encryption from the "C-bit" based approach. As much as
> > possible, I'm trying to not make it be Hyper-V specific, though
> > currently we have N=1 for hypervisors that offer the vTOM option, so
> > it's a little hard to generalize.
>
> Actually, it is very simple to generalize: vTOM and the paravisor and
> VMPL are all part of the effort to support unenlightened, unmodified
> guests with SNP.
>
> So, if KVM wants to run Windows NT 4.0 guests as SNP guests, then it
> probably would need the same contraptions.
Yes, agreed. My point about generalization is that Hyper-V is the only
actual implementation today. Edge cases, like whether the IO-APIC is
accessed as encrypted or as decrypted don't have a pattern yet. But
that's not a blocker. Such cases can be resolved or special-cased later
when/if N > 1.
>
> > With the thinking oriented that way, a Linux guest on Hyper-V using
> > TDX will run with CC_VENDOR_INTEL. A Linux guest on Hyper-V that
> > is fully enlightened to use the "C-bit" will run with CC_VENDOR_AMD.
>
> Right.
Good. We're in agreement. :-)
>
> > Dexuan Cui just posted a patch set for initial TDX support on Hyper-V,
> > and I think that runs with CC_VENDOR_INTEL (Dexuan -- correct me if
> > I'm wrong about that -- I haven't reviewed your patches yet).
I confirmed with Dexuan that his new patch set for TDX guests on Hyper-V
has the guest running with CC_VENDOR_INTEL, which is what we want.
> > Tianyu Lan
> > has a patch set out for Hyper-V guests using the "C-bit". That patch set
> > still uses CC_VENDOR_HYPERV. Tianyu and I need to work through
> > whether his patch set can run with CC_VENDOR_AMD like everyone
> > else using the "C-bit" approach.
I haven't followed up with Tianyu yet.
>
> So I'm not sure the vendor is the right approach here. I guess we need
> to specify the *type* of guest being supported.
Yes, calling it the "vendor" turns out to not quite be right because in
the AMD case, the technology/architecture/scheme/"type" (or
whatever you want to call it) is not 1:1 with the vendor. Intel has just
one (TDX) while AMD has two (C-bit and vTOM). "vendor" is just a label,
but we should get the label right to avoid future confusion. The key point
is that we'll have three top-level types:
* TDX
* AMD with C-bit (and this has some sub-types)
* AMD with vTOM
The CC_ATTR_* values are then derived from the "type".
>
> > Yes, the polarity of the AMD vTOM bit matches the polarity of the
> > TDX GPA.SHARED bit, and is the opposite polarity of the AMD "C-bit".
> > I'll add a comment to that effect.
> >
> > Anyway, that's where I think this should go. Does it make sense?
> > Other thoughts?
>
> I think all that polarity doesn't matter as long as we abstract it away
> with, "mark encrypted" and "mark decrypted".
Agreed.
Michael
next prev parent reply other threads:[~2022-11-23 0:59 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 18:41 [Patch v3 00/14] Add PCI pass-thru support to Hyper-V Confidential VMs Michael Kelley
2022-11-16 18:41 ` [Patch v3 01/14] x86/ioremap: Fix page aligned size calculation in __ioremap_caller() Michael Kelley
2022-11-21 13:32 ` Borislav Petkov
2022-11-21 16:40 ` Michael Kelley (LINUX)
2022-11-21 19:45 ` Borislav Petkov
2022-11-21 21:02 ` Michael Kelley (LINUX)
2022-11-21 18:14 ` Dave Hansen
2022-11-21 21:04 ` Michael Kelley (LINUX)
2022-11-21 21:08 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 02/14] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute Michael Kelley
2022-11-17 21:39 ` Sathyanarayanan Kuppuswamy
2022-11-21 13:50 ` Borislav Petkov
2022-11-21 16:43 ` Michael Kelley (LINUX)
2022-11-21 19:47 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 03/14] x86/hyperv: Reorder code in prep for subsequent patch Michael Kelley
2022-11-16 18:41 ` [Patch v3 04/14] Drivers: hv: Explicitly request decrypted in vmap_pfn() calls Michael Kelley
2022-11-16 18:41 ` [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently Michael Kelley
2022-11-16 20:35 ` Tom Lendacky
2022-11-16 21:15 ` Tom Lendacky
2022-11-18 2:59 ` Michael Kelley (LINUX)
2022-11-17 21:47 ` Sathyanarayanan Kuppuswamy
2022-11-18 2:55 ` Michael Kelley (LINUX)
2022-11-21 14:39 ` Borislav Petkov
2022-11-21 22:06 ` Sathyanarayanan Kuppuswamy
2022-11-22 17:59 ` Michael Kelley (LINUX)
2022-11-28 10:50 ` Borislav Petkov
2022-11-28 2:52 ` Dexuan Cui
2022-11-28 14:15 ` Tom Lendacky
2022-11-28 18:06 ` Dexuan Cui
2022-11-21 14:40 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 06/14] init: Call mem_encrypt_init() after Hyper-V hypercall init is done Michael Kelley
2022-11-16 21:14 ` Tom Lendacky
2022-11-21 14:46 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms Michael Kelley
2022-11-17 2:59 ` Tianyu Lan
2022-11-21 15:03 ` Borislav Petkov
2022-11-22 18:22 ` Michael Kelley (LINUX)
2022-11-22 18:30 ` Dave Hansen
2022-11-22 22:02 ` Michael Kelley (LINUX)
2022-11-22 22:18 ` Borislav Petkov
2022-11-23 0:59 ` Michael Kelley (LINUX) [this message]
2022-11-28 14:38 ` Michael Kelley (LINUX)
2022-11-28 16:33 ` Borislav Petkov
2022-11-28 16:59 ` Michael Kelley (LINUX)
2022-11-28 17:24 ` Borislav Petkov
2022-11-28 17:55 ` Michael Kelley (LINUX)
2022-11-28 19:56 ` Borislav Petkov
2022-11-29 1:15 ` Michael Kelley (LINUX)
2022-11-29 8:40 ` Borislav Petkov
2022-11-29 15:49 ` Michael Kelley (LINUX)
2022-11-29 17:47 ` Borislav Petkov
2022-11-30 16:11 ` Michael Kelley (LINUX)
2022-11-16 18:41 ` [Patch v3 08/14] swiotlb: Remove bounce buffer remapping for Hyper-V Michael Kelley
2022-11-16 18:41 ` [Patch v3 09/14] Drivers: hv: vmbus: Remove second mapping of VMBus monitor pages Michael Kelley
2022-11-16 18:41 ` [Patch v3 10/14] Drivers: hv: vmbus: Remove second way of mapping ring buffers Michael Kelley
2022-11-16 18:41 ` [Patch v3 11/14] hv_netvsc: Remove second mapping of send and recv buffers Michael Kelley
2022-11-16 18:41 ` [Patch v3 12/14] Drivers: hv: Don't remap addresses that are above shared_gpa_boundary Michael Kelley
2022-11-16 18:41 ` [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space Michael Kelley
2022-11-17 15:16 ` Wei Liu
2022-11-17 16:14 ` Michael Kelley (LINUX)
2022-11-17 17:01 ` Wei Liu
2022-11-17 16:32 ` Sean Christopherson
2022-11-17 17:00 ` Wei Liu
2022-11-17 18:33 ` Haiyang Zhang
2022-11-18 2:38 ` Michael Kelley (LINUX)
2022-11-16 18:41 ` [Patch v3 14/14] PCI: hv: Enable PCI pass-thru devices in Confidential VMs Michael Kelley
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