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From: Andi Kleen <ak@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>,
	"Kuppuswamy,
	Sathyanarayanan"  <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Richard Henderson <rth@twiddle.net>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	James E J Bottomley <James.Bottomley@hansenpartnership.com>,
	Helge Deller <deller@gmx.de>,
	"David S . Miller" <davem@davemloft.net>,
	Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
	Peter H Anvin <hpa@zytor.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Kirill Shutemov <kirill.shutemov@linux.intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
	X86 ML <x86@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>,
	linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
Date: Mon, 23 Aug 2021 19:14:18 -0700	[thread overview]
Message-ID: <d992b5af-8d57-6aa6-bd49-8e2b8d832b19@linux.intel.com> (raw)
In-Reply-To: <CAPcyv4iJVQKJ3bVwZhD08c8GNEP0jW2gx=H504NXcYK5o2t01A@mail.gmail.com>


On 8/23/2021 6:04 PM, Dan Williams wrote:
> On Mon, Aug 23, 2021 at 5:31 PM Kuppuswamy, Sathyanarayanan
> <sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>>
>>
>> On 8/23/21 4:56 PM, Michael S. Tsirkin wrote:
>>>> Add a new variant of pci_iomap for mapping all PCI resources
>>>> of a devices as shared memory with a hypervisor in a confidential
>>>> guest.
>>>>
>>>> Signed-off-by: Andi Kleen<ak@linux.intel.com>
>>>> Signed-off-by: Kuppuswamy Sathyanarayanan<sathyanarayanan.kuppuswamy@linux.intel.com>
>>> I'm a bit puzzled by this part. So why should the guest*not*  map
>>> pci memory as shared? And if the answer is never (as it seems to be)
>>> then why not just make regular pci_iomap DTRT?
>> It is in the context of confidential guest (where VMM is un-trusted). So
>> we don't want to make all PCI resource as shared. It should be allowed
>> only for hardened drivers/devices.
> That's confusing, isn't device authorization what keeps unaudited
> drivers from loading against untrusted devices? I'm feeling like
> Michael that this should be a detail that drivers need not care about
> explicitly, in which case it does not need to be exported because the
> detail can be buried in lower levels.

We originally made it default (similar to AMD), but it during code audit 
we found a lot of drivers who do ioremap early outside the probe 
function. Since it would be difficult to change them all we made it 
opt-in, which ensures that only drivers that have been enabled can talk 
with the host at all and can't be attacked. That made the problem of 
hardening all these drivers a lot more practical.

Currently we only really need virtio and MSI-X shared, so for changing 
two places in the tree you avoid a lot of headache elsewhere.

Note there is still a command line option to override if you want to 
allow and load other drivers.

-Andi


  reply	other threads:[~2021-08-24  2:14 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05  0:52 [PATCH v4 00/15] Add TDX Guest Support (shared-mm support) Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 01/15] x86/mm: Move force_dma_unencrypted() to common code Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 02/15] x86/tdx: Exclude Shared bit from physical_mask Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 03/15] x86/tdx: Make pages shared in ioremap() Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 04/15] x86/tdx: Add helper to do MapGPA hypercall Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 05/15] x86/tdx: Make DMA pages shared Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 06/15] x86/kvm: Use bounce buffers for TD guest Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 07/15] x86/tdx: ioapic: Add shared bit for IOAPIC base address Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 08/15] x86/tdx: Enable shared memory protected guest flags for TDX guest Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 09/15] pci: Consolidate pci_iomap* and pci_iomap*wc Kuppuswamy Sathyanarayanan
2021-08-12 19:43   ` Bjorn Helgaas
2021-08-12 22:11     ` Andi Kleen
2021-08-12 22:29     ` Kuppuswamy, Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 10/15] asm/io.h: Add ioremap_shared fallback Kuppuswamy Sathyanarayanan
2021-08-12 19:46   ` Bjorn Helgaas
2021-08-13  7:58   ` Christoph Hellwig
2021-08-05  0:52 ` [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range} Kuppuswamy Sathyanarayanan
2021-08-13  8:02   ` Christoph Hellwig
2021-08-23 23:56   ` Michael S. Tsirkin
2021-08-24  0:30     ` Kuppuswamy, Sathyanarayanan
2021-08-24  1:04       ` Dan Williams
2021-08-24  2:14         ` Andi Kleen [this message]
2021-08-24  9:47           ` Michael S. Tsirkin
2021-08-24 17:20             ` Andi Kleen
2021-08-24 18:55               ` Bjorn Helgaas
2021-08-24 20:14                 ` Andi Kleen
2021-08-24 20:31                   ` Bjorn Helgaas
2021-08-24 20:50                     ` Andi Kleen
2021-08-24 21:05                       ` Dan Williams
2021-08-25 14:52                       ` Bjorn Helgaas
2021-08-24 21:55                 ` Rajat Jain
2021-08-29 15:27               ` Michael S. Tsirkin
2021-08-29 16:17                 ` Andi Kleen
2021-08-29 22:26                   ` Michael S. Tsirkin
2021-08-30  5:11                     ` Andi Kleen
2021-08-30 20:59                       ` Michael S. Tsirkin
2021-08-31  0:23                         ` Andi Kleen
2021-09-10  9:54                           ` Michael S. Tsirkin
2021-09-10 16:34                             ` Andi Kleen
2021-09-11 23:54                               ` Michael S. Tsirkin
2021-09-13  5:53                                 ` Michael S. Tsirkin
2021-09-24 22:43                                 ` Andi Kleen
2021-09-27  9:07                                   ` Michael S. Tsirkin
2021-08-24 21:56         ` Rajat Jain
2021-08-24 21:59           ` Dan Williams
2021-08-24  7:07       ` Christoph Hellwig
2021-08-24 17:04         ` Andi Kleen
2021-08-29 15:34           ` Michael S. Tsirkin
2021-08-29 16:43             ` Andi Kleen
2021-08-24  9:12       ` Michael S. Tsirkin
2021-08-05  0:52 ` [PATCH v4 12/15] pci: Mark MSI data shared Kuppuswamy Sathyanarayanan
2021-08-13  8:07   ` Christoph Hellwig
2021-08-05  0:52 ` [PATCH v4 13/15] virtio: Use shared mappings for virtio PCI devices Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 14/15] x86/tdx: Implement ioremap_shared for x86 Kuppuswamy Sathyanarayanan
2021-08-05  0:52 ` [PATCH v4 15/15] x86/tdx: Add cmdline option to force use of ioremap_shared Kuppuswamy Sathyanarayanan

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