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: Tue, 22 Nov 2022 18:22:46 +0000 [thread overview]
Message-ID: <BYAPR21MB16886AF404739449CA467B1AD70D9@BYAPR21MB1688.namprd21.prod.outlook.com> (raw)
In-Reply-To: <Y3uTK3rBV6eXSJnC@zn.tnic>
From: Borislav Petkov <bp@alien8.de> Sent: Monday, November 21, 2022 7:03 AM
>
> On Wed, Nov 16, 2022 at 10:41:30AM -0800, Michael Kelley wrote:
> ...
>
> > @@ -108,6 +115,7 @@ u64 cc_mkenc(u64 val)
> > switch (vendor) {
> > case CC_VENDOR_AMD:
> > return val | cc_mask;
> > + case CC_VENDOR_HYPERV:
> > case CC_VENDOR_INTEL:
> > return val & ~cc_mask;
> > default:
> > @@ -121,6 +129,7 @@ u64 cc_mkdec(u64 val)
> > switch (vendor) {
> > case CC_VENDOR_AMD:
> > return val & ~cc_mask;
> > + case CC_VENDOR_HYPERV:
> > case CC_VENDOR_INTEL:
> > return val | cc_mask;
> > default:
>
> Uuuh, this needs a BIG FAT COMMENT.
>
> You're running on SNP and yet the enc/dec meaning is flipped. And that's
> because of vTOM.
>
> What happens if you have other types of SNP-based VMs on HyperV? The
> isolation VMs thing? Or is that the same?
>
> What happens when you do TDX guests with HyperV?
>
> This becomes wrong then.
>
> I think you need a more finer-grained check here in the sense of "is it
> a HyperV guest using a paravisor and vTOM is enabled" or so.
>
> Otherwise, I like the removal of the HyperV-specific checks ofc.
>
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.
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.
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.
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). 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.
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?
Michael
next prev parent reply other threads:[~2022-11-22 18:22 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) [this message]
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)
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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