From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Dave Hansen <dave.hansen@intel.com>,
Borislav Petkov <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
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Subject: RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted
Date: Thu, 9 Feb 2023 17:29:13 +0000 [thread overview]
Message-ID: <BYAPR21MB16886A07302A09B96FFFAE84D7D99@BYAPR21MB1688.namprd21.prod.outlook.com> (raw)
In-Reply-To: <76566fc4-d6be-8ebf-7e9d-d0b7918cb880@intel.com>
From: Dave Hansen <dave.hansen@intel.com> Sent: Wednesday, February 8, 2023 7:10 AM
>
> On 2/7/23 16:18, Michael Kelley (LINUX) wrote:
> > In v2 of this patch series, you had concerns about CC_ATTR_PARAVISOR being too
> > generic. [1] After some back-and-forth discussion in this thread, Boris is back to
> > preferring it. Can you live with CC_ATTR_PARAVISOR? Just trying to reach
> > consensus ...
>
> I still think it's too generic. Even the comment was trying to be too
> generic:
>
> > + /**
> > + * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor
> > + *
> > + * The platform/OS is running as a guest/virtual machine with
> > + * a paravisor in VMPL0. Having a paravisor affects things
> > + * like whether the I/O APIC is emulated and operates in the
> > + * encrypted or decrypted portion of the guest physical address
> > + * space.
> > + *
> > + * Examples include Hyper-V SEV-SNP guests using vTOM.
> > + */
> > + CC_ATTR_HAS_PARAVISOR,
>
> This doesn't help me figure out when I should use CC_ATTR_HAS_PARAVISOR
> really at all. It "operates in the encrypted or decrypted portion..."
> Which one is it? Should I be adding or removing encryption on the
> mappings for paravisors?
>
> That's opposed to:
>
> > + /**
> > + * @CC_ATTR_ACCESS_IOAPIC_ENCRYPTED: Guest VM IO-APIC is encrypted
> > + *
> > + * The platform/OS is running as a guest/virtual machine with
> > + * an IO-APIC that is emulated by a paravisor running in the
> > + * guest VM context. As such, the IO-APIC is accessed in the
> > + * encrypted portion of the guest physical address space.
> > + *
> > + * Examples include Hyper-V SEV-SNP guests using vTOM.
> > + */
> > + CC_ATTR_ACCESS_IOAPIC_ENCRYPTED,
>
> Which makes this code almost stupidly obvious:
>
> > - flags = pgprot_decrypted(flags);
> > + if (!cc_platform_has(CC_ATTR_ACCESS_IOAPIC_ENCRYPTED))
> > + flags = pgprot_decrypted(flags);
>
> "Oh, if it's access is not encrypted, then get the decrypted version of
> the flags."
>
> Compare that to:
>
> if (!cc_platform_has(CC_ATTR_PARAVISOR))
> flags = pgprot_decrypted(flags);
>
> Which is a big fat WTF. Because a paravisor "operates in the encrypted
> or decrypted portion..." So is this if() condition correct or inverted?
> It's utterly impossible to tell because of how generic the option is.
>
> The only way to make sense of the generic thing is to do:
>
> /* Paravisors have a decrypted IO-APIC mapping: */
> if (!cc_platform_has(CC_ATTR_PARAVISOR))
> flags = pgprot_decrypted(flags);
>
> at every site to state the assumption and make the connection between
> paravisors and the behavior. If you want to go do _that_, then fine by
> me. But, at that point, the naming is pretty worthless because you
> could also have said "goldfish" instead of "paravisor" and it makes an
> equal amount of sense:
>
> /* Goldfish have a decrypted IO-APIC mapping: */
> if (!cc_platform_has(CC_ATTR_GOLDFISH))
> flags = pgprot_decrypted(flags);
>
> I get it, naming is hard.
Boris --
Any further comments? Trying to reach consensus. A
solution aligned with Dave's arguments would keep the current
CC_ATTR_ACCESS_IOAPIC_ENCRYPTED, and add
CC_ATTR_ACCESS_TPM_ENCRYPTED to cover the TPM case,
which decouples the two.
Yes, naming is hard. Reaching consensus on naming is even
harder. :-)
Michael
next prev parent reply other threads:[~2023-02-09 17:29 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-12 21:42 [PATCH v5 00/14] Add PCI pass-thru support to Hyper-V Confidential VMs Michael Kelley
2023-01-12 21:42 ` [PATCH v5 01/14] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute Michael Kelley
2023-01-12 21:42 ` [PATCH v5 02/14] x86/hyperv: Reorder code to facilitate future work Michael Kelley
2023-01-12 21:42 ` [PATCH v5 03/14] Drivers: hv: Explicitly request decrypted in vmap_pfn() calls Michael Kelley
2023-01-12 21:42 ` [PATCH v5 04/14] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently Michael Kelley
2023-01-12 21:42 ` [PATCH v5 05/14] init: Call mem_encrypt_init() after Hyper-V hypercall init is done Michael Kelley
2023-01-12 21:42 ` [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted Michael Kelley
2023-01-20 20:15 ` Borislav Petkov
2023-01-21 4:10 ` Michael Kelley (LINUX)
2023-01-25 14:55 ` Borislav Petkov
2023-02-02 5:49 ` Michael Kelley (LINUX)
2023-02-07 12:41 ` Borislav Petkov
2023-02-07 19:01 ` Michael Kelley (LINUX)
2023-02-07 19:33 ` Borislav Petkov
2023-02-07 19:48 ` Michael Kelley (LINUX)
2023-02-07 19:54 ` Borislav Petkov
2023-02-07 19:57 ` Michael Kelley (LINUX)
2023-02-08 0:18 ` Michael Kelley (LINUX)
2023-02-08 15:09 ` Dave Hansen
2023-02-09 17:29 ` Michael Kelley (LINUX) [this message]
2023-02-08 17:23 ` Dave Hansen
2023-02-09 17:47 ` Michael Kelley (LINUX)
2023-02-10 18:41 ` Sean Christopherson
2023-02-10 18:58 ` Dave Hansen
2023-02-10 19:03 ` Borislav Petkov
2023-02-10 19:15 ` Michael Kelley (LINUX)
2023-02-10 19:36 ` Borislav Petkov
2023-02-10 19:58 ` Dave Hansen
2023-02-10 20:50 ` Sean Christopherson
2023-02-10 20:57 ` Sean Christopherson
2023-02-10 21:27 ` Michael Kelley (LINUX)
2023-02-10 23:47 ` Sean Christopherson
2023-02-14 7:45 ` Michael Kelley (LINUX)
2023-02-16 13:32 ` Borislav Petkov
2023-02-16 16:16 ` Michael Kelley (LINUX)
2023-02-16 17:06 ` Borislav Petkov
2023-02-17 6:16 ` Michael Kelley (LINUX)
2023-02-17 14:55 ` Borislav Petkov
2023-02-22 22:13 ` Sean Christopherson
2023-02-22 22:33 ` Borislav Petkov
2023-02-22 22:54 ` Sean Christopherson
2023-02-22 23:34 ` Borislav Petkov
2023-02-23 1:21 ` Sean Christopherson
2023-02-23 10:45 ` Borislav Petkov
2023-02-23 20:01 ` Michael Kelley (LINUX)
2023-02-23 20:27 ` Dave Hansen
2023-03-06 21:51 ` Borislav Petkov
2023-03-09 11:12 ` David Woodhouse
2023-03-09 11:59 ` Borislav Petkov
2023-03-09 13:00 ` David Woodhouse
2023-03-09 14:19 ` Tom Lendacky
2023-03-09 14:36 ` Jörg Rödel
2023-03-09 14:45 ` Borislav Petkov
2023-03-09 15:45 ` David Woodhouse
2023-03-09 16:34 ` Borislav Petkov
2023-03-10 10:05 ` David Woodhouse
2023-02-23 20:26 ` Dave Hansen
2023-02-23 20:41 ` Dave Hansen
2023-02-23 20:51 ` Michael Kelley (LINUX)
2023-02-23 21:07 ` Sean Christopherson
2023-02-23 21:15 ` Michael Kelley (LINUX)
2023-02-23 21:24 ` Dave Hansen
2023-01-12 21:42 ` [PATCH v5 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms Michael Kelley
2023-01-12 21:42 ` [PATCH v5 08/14] swiotlb: Remove bounce buffer remapping for Hyper-V Michael Kelley
2023-01-12 21:42 ` [PATCH v5 09/14] Drivers: hv: vmbus: Remove second mapping of VMBus monitor pages Michael Kelley
2023-01-12 21:42 ` [PATCH v5 10/14] Drivers: hv: vmbus: Remove second way of mapping ring buffers Michael Kelley
2023-01-12 21:42 ` [PATCH v5 11/14] hv_netvsc: Remove second mapping of send and recv buffers Michael Kelley
2023-01-12 21:42 ` [PATCH v5 12/14] Drivers: hv: Don't remap addresses that are above shared_gpa_boundary Michael Kelley
2023-01-12 21:42 ` [PATCH v5 13/14] PCI: hv: Add hypercalls to read/write MMIO space Michael Kelley
2023-01-12 21:42 ` [PATCH v5 14/14] PCI: hv: Enable PCI pass-thru devices in Confidential VMs Michael Kelley
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