From: "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "hpa@zytor.com" <hpa@zytor.com>,
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Subject: RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted
Date: Thu, 2 Feb 2023 05:49:44 +0000 [thread overview]
Message-ID: <BYAPR21MB16883BB6178DDEEA10FD1F1CD7D69@BYAPR21MB1688.namprd21.prod.outlook.com> (raw)
In-Reply-To: <Y9FC7Dpzr5Uge/Mi@zn.tnic>
From: Borislav Petkov <bp@alien8.de> Sent: Wednesday, January 25, 2023 6:56 AM
>
> On Sat, Jan 21, 2023 at 04:10:23AM +0000, Michael Kelley (LINUX) wrote:
[snip]
>
> > But in any case, the whole point of cc_platform_has() is to provide a level of
> > abstraction from the hardware registers, and it's fully safe to use on every x86
> > bare-metal system or VM. And while I don't anticipate it now, maybe there's
> > some future scheme where a paravisor-like entity could be used with Intel
> > TDX. It seems like using a cc_platform_has() abstraction is better than directly
> > accessing the MSR.
>
> That's fine but we're talking about this particular implementation and that is
> vTOM-like with the address space split. If TDX does address space split later,
> we can accomodate it too. (Although I think they are not interested in this).
>
> And if you really want to use cc_platform_has(), we could do
>
> cc_platform_has(CC_ADDRESS_SPACE_SPLIT_ON_A_PARAVISOR)
>
> or something with a better name.
I do think it makes sense to use the cc_platform_has() abstraction. It's
then a question of agreeing on how to name the attribute. We've
discussed various approaches in different versions of this patch series:
v1 & v2: CC_ATTR_HAS_PARAVISOR
v3: CC_ATTR_EMULATED_IOAPIC
v4 & v5: CC_ATTR_ACCESS_IOAPIC_ENCRYPTED
I could do:
1. CC_ATTR_PARAVISOR_SPLIT_ADDRESS_SPACE, which is similar to
what I had for v1 & v2. At the time, somebody commented that
this might be a bit too general.
2. Keep CC_ATTR_ACCESS_IOAPIC_ENCRYPTED and add
CC_ATTR_ACCESS_TPM_ENCRYPTED, which would decouple them
3. CC_ATTR_ACCESS_IOAPIC_AND_TPM_ENCRYPTED, which is very
narrow and specific.
I have weak preference for #1 above, but I could go with any of them.
What's your preference?
> > My resolution of the TPM driver issue is admittedly a work-around. I think
> > of it as temporary in anticipation of future implementations of PCIe TDISP
> > hardware, which allows PCI devices to DMA directly into guest encrypted
> > memory.
>
> Yap, that sounds real nice.
>
> > TDISP also places the device's BAR values in an encrypted portion
> > of the GPA space. Assuming TDISP hardware comes along in the next couple
> > of years, Linux will need a robust way to deal with a mix of PCI devices
> > being in unencrypted and encrypted GPA space. I don't know how a
> > specific device will be mapped correctly, but I hope it can happen in the
> > generic PCI code, and not by modifying each device driver.
>
> I guess those devices would advertize that capability somehow so that code can
> query it and act accordingly.
>
> > It's probably premature to build that robust mechanism now, but when it comes,
> > my work-around would be replaced.
>
> It would be replaced if it doesn't have any users. By the looks of it, it'll
> soon grow others and then good luck removing it.
>
> > With all that in mind, I don't want to modify the TPM driver to special-case
> > its MMIO space being encrypted. FWIW, the TPM driver today uses
> > devm_ioremap_resource() to do the mapping, which defaults to mapping
> > decrypted except for the exceptions implemented in __ioremap_caller().
> > There's no devm_* option for specifying encrypted.
>
> You mean, it is hard to add a DEVM_IOREMAP_ENCRYPTED type which will have
> __devm_ioremap() call ioremap_encrypted()?
>
> Or define a IORESOURCE_ENCRYPTED and pass it through the ioresource flags?
>
> Why is that TPM driver so precious that it can be touched and the arch code
> would have to accept hacks?
>
> > Handling decrypted vs. encrypted in the driver would require extending the
> > driver API to provide an "encrypted" option, and that seems like going in the
> > wrong long-term direction.
>
> Sorry, I can't follow here.
>
For v6 of the patch series, I've coded devm_ioremap_resource_enc() to call
__devm_ioremap(), which then calls ioremap_encrypted(). I've updated the
TPM driver to use cc_platform_has() with whatever attribute name we agree
on to decide between devm_ioremap_resource_enc() and
devm_ioremap_resource().
If this approach is OK with the TPM driver maintainers, I'm good with it.
More robust handling of a mix of encrypted and decrypted devices can get
sorted out later.
Michael
next prev parent reply other threads:[~2023-02-02 5:51 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) [this message]
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)
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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