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From: Dan Williams <dan.j.williams@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kuppuswamy Sathyanarayanan 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [PATCH v5 12/16] PCI: Add pci_iomap_host_shared(), pci_iomap_host_shared_range()
Date: Sat, 9 Oct 2021 13:39:57 -0700	[thread overview]
Message-ID: <CAPcyv4hDhjRXYCX_aiOboLF0eaTo6VySbZDa5NQu2ed9Ty2Ekw@mail.gmail.com> (raw)
In-Reply-To: <20211009053103-mutt-send-email-mst@kernel.org>

On Sat, Oct 9, 2021 at 2:53 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Oct 08, 2021 at 05:37:07PM -0700, Kuppuswamy Sathyanarayanan wrote:
> > From: Andi Kleen <ak@linux.intel.com>
> >
> > For Confidential VM guests like TDX, the host is untrusted and hence
> > the devices emulated by the host or any data coming from the host
> > cannot be trusted. So the drivers that interact with the outside world
> > have to be hardened by sharing memory with host on need basis
> > with proper hardening fixes.
> >
> > For the PCI driver case, to share the memory with the host add
> > pci_iomap_host_shared() and pci_iomap_host_shared_range() APIs.
> >
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>
> So I proposed to make all pci mappings shared, eliminating the need
> to patch drivers.
>
> To which Andi replied
>         One problem with removing the ioremap opt-in is that
>         it's still possible for drivers to get at devices without going through probe.
>
> To which Greg replied:
> https://lore.kernel.org/all/YVXBNJ431YIWwZdQ@kroah.com/
>         If there are in-kernel PCI drivers that do not do this, they need to be
>         fixed today.
>
> Can you guys resolve the differences here?

I agree with you and Greg here. If a driver is accessing hardware
resources outside of the bind lifetime of one of the devices it
supports, and in a way that neither modrobe-policy nor
device-authorization -policy infrastructure can block, that sounds
like a bug report. Fix those drivers instead of sprinkling
ioremap_shared in select places and with unclear rules about when a
driver is allowed to do "shared" mappings. Let the new
device-authorization mechanism (with policy in userspace) be the
central place where all of these driver "trust" issues are managed.

> And once they are resolved, mention this in the commit log so
> I don't get to re-read the series just to find out nothing
> changed in this respect?
>
> I frankly do not believe we are anywhere near being able to harden
> an arbitrary kernel config against attack.
> How about creating a defconfig that makes sense for TDX then?
> Anyone deviating from that better know what they are doing,
> this API tweaking is just putting policy into the kernel  ...

Right, userspace authorization policy and select driver fixups seems
to be the answer to the raised concerns.

  reply	other threads:[~2021-10-09 20:40 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-09  0:36 [PATCH v5 00/16] Add TDX Guest Support (shared-mm support) Kuppuswamy Sathyanarayanan
2021-10-09  0:36 ` [PATCH v5 01/16] x86/mm: Move force_dma_unencrypted() to common code Kuppuswamy Sathyanarayanan
2021-10-20 16:11   ` Tom Lendacky
2021-10-20 16:43     ` Sathyanarayanan Kuppuswamy
2021-10-09  0:36 ` [PATCH v5 02/16] x86/tdx: Get TD execution environment information via TDINFO Kuppuswamy Sathyanarayanan
2021-10-09  0:36 ` [PATCH v5 03/16] x86/tdx: Exclude Shared bit from physical_mask Kuppuswamy Sathyanarayanan
2021-11-05 22:11   ` Sean Christopherson
2021-11-08 14:45     ` Kirill A. Shutemov
2021-10-09  0:36 ` [PATCH v5 04/16] x86/tdx: Make pages shared in ioremap() Kuppuswamy Sathyanarayanan
2021-10-20 16:03   ` Tom Lendacky
2021-10-20 16:41     ` Sathyanarayanan Kuppuswamy
2021-10-09  0:37 ` [PATCH v5 05/16] x86/tdx: Add helper to do MapGPA hypercall Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 06/16] x86/tdx: Make DMA pages shared Kuppuswamy Sathyanarayanan
2021-10-20 16:33   ` Tom Lendacky
2021-10-20 16:45     ` Sathyanarayanan Kuppuswamy
2021-10-20 17:22       ` Tom Lendacky
2021-10-20 17:26         ` Sathyanarayanan Kuppuswamy
2021-10-09  0:37 ` [PATCH v5 07/16] x86/kvm: Use bounce buffers for TD guest Kuppuswamy Sathyanarayanan
2021-10-20 16:39   ` Tom Lendacky
2021-10-20 16:50     ` Sathyanarayanan Kuppuswamy
2021-10-20 17:26       ` Tom Lendacky
2021-10-09  0:37 ` [PATCH v5 08/16] x86/tdx: ioapic: Add shared bit for IOAPIC base address Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 09/16] x86/tdx: Enable shared memory confidential guest flags for TDX guest Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 10/16] PCI: Consolidate pci_iomap_range(), pci_iomap_wc_range() Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 11/16] asm/io.h: Add ioremap_host_shared fallback Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 12/16] PCI: Add pci_iomap_host_shared(), pci_iomap_host_shared_range() Kuppuswamy Sathyanarayanan
2021-10-09  9:53   ` Michael S. Tsirkin
2021-10-09 20:39     ` Dan Williams [this message]
2021-10-10 22:11       ` Andi Kleen
2021-10-12 17:42         ` Dan Williams
2021-10-12 18:35           ` Andi Kleen
2021-10-12 21:14             ` Dan Williams
2021-10-12 21:18               ` Michael S. Tsirkin
2021-10-12 21:24                 ` Andi Kleen
2021-10-12 21:28               ` Andi Kleen
2021-10-12 22:00                 ` Dan Williams
2021-10-18 12:13             ` Greg KH
2021-10-12 18:36         ` Reshetova, Elena
2021-10-12 18:38           ` Andi Kleen
2021-10-12 18:57             ` Reshetova, Elena
2021-10-12 19:13               ` Dan Williams
2021-10-12 19:49                 ` Andi Kleen
2021-10-12 21:11           ` Michael S. Tsirkin
2021-10-14  6:32             ` Reshetova, Elena
2021-10-14  6:57               ` Michael S. Tsirkin
2021-10-14  7:27                 ` Reshetova, Elena
2021-10-14  9:26                   ` Michael S. Tsirkin
2021-10-14 12:33                     ` Reshetova, Elena
2021-10-17 22:17                       ` Michael S. Tsirkin
2021-10-14 11:49                   ` Michael S. Tsirkin
2021-10-17 21:52               ` Thomas Gleixner
2021-10-18  7:03                 ` Reshetova, Elena
2021-10-18  0:55         ` Thomas Gleixner
2021-10-18  1:10           ` Thomas Gleixner
2021-10-18 12:08         ` Greg KH
2021-10-10 22:22     ` Andi Kleen
2021-10-11 11:59       ` Michael S. Tsirkin
2021-10-11 17:32         ` Andi Kleen
2021-10-11 18:22           ` Michael S. Tsirkin
2021-10-18 12:15         ` Greg KH
2021-10-18 13:17           ` Michael S. Tsirkin
2021-10-11  7:58   ` Christoph Hellwig
2021-10-11 17:23     ` Andi Kleen
2021-10-11 19:09       ` Michael S. Tsirkin
2021-10-12  5:31         ` Christoph Hellwig
2021-10-12 18:37           ` Andi Kleen
2021-10-09  0:37 ` [PATCH v5 13/16] PCI: Mark MSI data shared Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 14/16] virtio: Use shared mappings for virtio PCI devices Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 15/16] x86/tdx: Implement ioremap_host_shared for x86 Kuppuswamy Sathyanarayanan
2021-10-09  0:37 ` [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of ioremap_host_shared Kuppuswamy Sathyanarayanan
2021-10-09  1:45   ` Randy Dunlap
2021-10-09  2:10     ` Kuppuswamy, Sathyanarayanan
2021-10-09 11:04   ` Michael S. Tsirkin
2021-10-11  2:39     ` Andi Kleen
2021-10-11 12:04       ` Michael S. Tsirkin
2021-10-11 17:35         ` Andi Kleen
2021-10-11 18:28           ` Michael S. Tsirkin
2021-10-12 17:55             ` Andi Kleen
2021-10-12 20:59               ` Michael S. Tsirkin
2021-10-12 21:18                 ` Andi Kleen
2021-10-12 21:30                   ` Michael S. Tsirkin
2021-10-15  5:50                     ` Andi Kleen
2021-10-15  6:57                       ` Michael S. Tsirkin
2021-10-15 13:34                         ` Andi Kleen
2021-10-17 22:34                           ` Michael S. Tsirkin

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