KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "kevin.tian@intel.com" <kevin.tian@intel.com>,
	Vincent Stehle <Vincent.Stehle@arm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	"ashok.raj@intel.com" <ashok.raj@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Marc Zyngier <Marc.Zyngier@arm.com>,
	Will Deacon <Will.Deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	Robin Murphy <Robin.Murphy@arm.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"eric.auger.pro@gmail.com" <eric.auger.pro@gmail.com>
Subject: Re: [PATCH v8 26/29] vfio-pci: Register an iommu fault handler
Date: Tue, 18 Jun 2019 15:04:36 +0100
Message-ID: <77405d39-81a4-d9a8-5d35-27602199867a@arm.com> (raw)
In-Reply-To: <20190612115358.0d90b322@jacob-builder>

On 12/06/2019 19:53, Jacob Pan wrote:
>>> You are right, the worst case of the spurious PS is to terminate the
>>> group prematurely. Need to know the scope of the HW damage in case
>>> of mdev where group IDs can be shared among mdevs belong to the
>>> same PF.  
>>
>> But from the IOMMU fault API point of view, the full page request is
>> identified by both PRGI and PASID. Given that each mdev has its own
>> set of PASIDs, it should be easy to isolate page responses per mdev.
>>
> On Intel platform, devices sending page request with private data must
> receive page response with matching private data. If we solely depend
> on PRGI and PASID, we may send stale private data to the device in
> those incorrect page response. Since private data may represent PF
> device wide contexts, the consequence of sending page response with
> wrong private data may affect other mdev/PASID.
> 
> One solution we are thinking to do is to inject the sequence #(e.g.
> ktime raw mono clock) as vIOMMU private data into to the guest. Guest
> would return this fake private data in page response, then host will
> send page response back to the device that matches PRG1 and PASID and
> private_data.
> 
> This solution does not expose HW context related private data to the
> guest but need to extend page response in iommu uapi.
> 
> /**
>  * struct iommu_page_response - Generic page response information
>  * @version: API version of this structure
>  * @flags: encodes whether the corresponding fields are valid
>  *         (IOMMU_FAULT_PAGE_RESPONSE_* values)
>  * @pasid: Process Address Space ID
>  * @grpid: Page Request Group Index
>  * @code: response code from &enum iommu_page_response_code
>  * @private_data: private data for the matching page request
>  */
> struct iommu_page_response {
> #define IOMMU_PAGE_RESP_VERSION_1	1
> 	__u32	version;
> #define IOMMU_PAGE_RESP_PASID_VALID	(1 << 0)
> #define IOMMU_PAGE_RESP_PRIVATE_DATA	(1 << 1)
> 	__u32	flags;
> 	__u32	pasid;
> 	__u32	grpid;
> 	__u32	code;
> 	__u32	padding;
> 	__u64	private_data[2];
> };
> 
> There is also the change needed for separating storage for the real and
> fake private data.
> 
> Sorry for the last minute change, did not realize the HW implications.
> 
> I see this as a future extension due to limited testing, 

I'm wondering how we deal with:
(1) old userspace that won't fill the new private_data field in
page_response. A new kernel still has to support it.
(2) old kernel that won't recognize the new PRIVATE_DATA flag. Currently
iommu_page_response() rejects page responses with unknown flags.

I guess we'll need a two-way negotiation, where userspace queries
whether the kernel supports the flag (2), and the kernel learns whether
it should expect the private data to come back (1).

> perhaps for
> now, can you add paddings similar to page request? Make it 64B as well.

I don't think padding is necessary, because iommu_page_response is sent
by userspace to the kernel, unlike iommu_fault which is allocated by
userspace and filled by the kernel.

Page response looks a lot more like existing VFIO mechanisms, so I
suppose we'll wrap the iommu_page_response structure and include an
argsz parameter at the top:

	struct vfio_iommu_page_response {
		u32 argsz;
		struct iommu_page_response pr;
	};

	struct vfio_iommu_page_response vpr = {
		.argsz = sizeof(vpr),
		.pr = ...
		...
	};

	ioctl(devfd, VFIO_IOMMU_PAGE_RESPONSE, &vpr);

In that case supporting private data can be done by simply appending a
field at the end (plus the negotiation above).

Thanks,
Jean
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

  reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-26 16:09 [PATCH v8 00/29] SMMUv3 Nested Stage Setup Eric Auger
2019-05-26 16:09 ` [PATCH v8 01/29] driver core: Add per device iommu param Eric Auger
2019-05-26 16:09 ` [PATCH v8 02/29] iommu: Introduce device fault data Eric Auger
2019-05-26 16:09 ` [PATCH v8 03/29] iommu: Introduce device fault report API Eric Auger
2019-05-26 16:09 ` [PATCH v8 04/29] iommu: Add recoverable fault reporting Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 15:48     ` Jacob Pan
2019-05-26 16:09 ` [PATCH v8 05/29] iommu: Add a timeout parameter for PRQ response Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-06-04 10:52     ` Jean-Philippe Brucker
2019-06-04 15:50       ` Jacob Pan
2019-05-26 16:09 ` [PATCH v8 06/29] trace/iommu: Add sva trace events Eric Auger
2019-05-26 16:09 ` [PATCH v8 07/29] iommu: Use device fault trace event Eric Auger
2019-05-26 16:09 ` [PATCH v8 08/29] iommu: Introduce attach/detach_pasid_table API Eric Auger
2019-05-26 16:09 ` [PATCH v8 09/29] iommu: Introduce cache_invalidate API Eric Auger
2019-05-26 16:09 ` [PATCH v8 10/29] iommu: Introduce bind/unbind_guest_msi Eric Auger
2019-05-26 16:09 ` [PATCH v8 11/29] iommu/arm-smmu-v3: Maintain a SID->device structure Eric Auger
2019-05-26 16:09 ` [PATCH v8 12/29] iommu/smmuv3: Dynamically allocate s1_cfg and s2_cfg Eric Auger
2019-05-26 16:09 ` [PATCH v8 13/29] iommu/smmuv3: Get prepared for nested stage support Eric Auger
2019-05-26 16:09 ` [PATCH v8 14/29] iommu/smmuv3: Implement attach/detach_pasid_table Eric Auger
2019-05-26 16:09 ` [PATCH v8 15/29] iommu/smmuv3: Introduce __arm_smmu_tlb_inv_asid/s1_range_nosync Eric Auger
2019-05-26 16:09 ` [PATCH v8 16/29] iommu/smmuv3: Implement cache_invalidate Eric Auger
2019-05-26 16:09 ` [PATCH v8 17/29] dma-iommu: Implement NESTED_MSI cookie Eric Auger
2019-05-26 16:09 ` [PATCH v8 18/29] iommu/smmuv3: Nested mode single MSI doorbell per domain enforcement Eric Auger
2019-05-26 16:09 ` [PATCH v8 19/29] iommu/smmuv3: Enforce incompatibility between nested mode and HW MSI regions Eric Auger
2019-05-26 16:09 ` [PATCH v8 20/29] iommu/smmuv3: Implement bind/unbind_guest_msi Eric Auger
2019-05-26 16:09 ` [PATCH v8 21/29] iommu/smmuv3: Report non recoverable faults Eric Auger
2019-05-26 16:09 ` [PATCH v8 22/29] vfio: VFIO_IOMMU_ATTACH/DETACH_PASID_TABLE Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-05-26 16:09 ` [PATCH v8 23/29] vfio: VFIO_IOMMU_CACHE_INVALIDATE Eric Auger
2019-06-14 12:38   ` Liu, Yi L
2019-06-14 13:17     ` Auger Eric
2019-05-26 16:09 ` [PATCH v8 24/29] vfio: VFIO_IOMMU_BIND/UNBIND_MSI Eric Auger
2019-06-03 22:32   ` Alex Williamson
2019-06-07  8:30     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 25/29] vfio-pci: Add a new VFIO_REGION_TYPE_NESTED region type Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-07  8:28     ` Auger Eric
2019-06-07 12:47       ` Jean-Philippe Brucker
2019-06-07 16:29       ` Alex Williamson
2019-05-26 16:10 ` [PATCH v8 26/29] vfio-pci: Register an iommu fault handler Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 16:11     ` Auger Eric
2019-06-05 22:45       ` Jacob Pan
2019-06-06 18:54         ` Jean-Philippe Brucker
2019-06-06 20:29           ` Jacob Pan
2019-06-07  7:02             ` Auger Eric
2019-06-07 10:28             ` Jean-Philippe Brucker
2019-06-07 17:43               ` Jacob Pan
2019-06-10 12:45                 ` Jean-Philippe Brucker
2019-06-10 21:31                   ` Jacob Pan
2019-06-11 13:14                     ` Jean-Philippe Brucker
2019-06-12 18:53                       ` Jacob Pan
2019-06-18 14:04                         ` Jean-Philippe Brucker [this message]
2019-06-19  0:19                           ` Jacob Pan
2019-06-19 11:44                             ` Jean-Philippe Brucker
2019-07-11 13:07                           ` Auger Eric
2019-06-07 12:48   ` Jean-Philippe Brucker
2019-06-07 14:18     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 27/29] vfio_pci: Allow to mmap the fault queue Eric Auger
2019-05-26 16:10 ` [PATCH v8 28/29] vfio-pci: Add VFIO_PCI_DMA_FAULT_IRQ_INDEX Eric Auger
2019-06-03 22:31   ` Alex Williamson
2019-06-04 16:11     ` Auger Eric
2019-05-26 16:10 ` [PATCH v8 29/29] vfio: Document nested stage control Eric Auger

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=77405d39-81a4-d9a8-5d35-27602199867a@arm.com \
    --to=jean-philippe.brucker@arm.com \
    --cc=Marc.Zyngier@arm.com \
    --cc=Robin.Murphy@arm.com \
    --cc=Vincent.Stehle@arm.com \
    --cc=Will.Deacon@arm.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=eric.auger.pro@gmail.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.jun.pan@linux.intel.com \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-kernel@vger.kernel.org \
    --cc=yi.l.liu@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu kvmarm@archiver.kernel.org
	public-inbox-index kvmarm


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/edu.columbia.cs.lists.kvmarm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox