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Re: [Qemu-devel] [PATCH v3 0/2] intel-iommu: add support for 5-level vir

From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH v3 0/2] intel-iommu: add support for 5-level virtual IOMMU.
Date: Mon, 14 Jan 2019 23:02:28 -0500

On Wed, Dec 12, 2018 at 09:05:37PM +0800, Yu Zhang wrote:
> Intel's upcoming processors will extend maximum linear address width to
> 57 bits, and introduce 5-level paging for CPU. Meanwhile, the platform
> will also extend the maximum guest address width for IOMMU to 57 bits,
> thus introducing the 5-level paging for 2nd level translation(See chapter
> 3 in Intel Virtualization Technology for Directed I/O). 
> This patch series extends the current logic to support a wider address width.
> A 5-level paging capable IOMMU(for 2nd level translation) can be rendered
> with configuration "device intel-iommu,x-aw-bits=57".
> Also, kvm-unit-tests were updated to verify this patch series. Patch for
> the test was sent out at: https://www.spinics.net/lists/kvm/msg177425.html.
> Note: this patch series checks the existance of 5-level paging in the host
> and in the guest, and rejects configurations for 57-bit IOVA if either check
> fails(VTD-d hardware shall not support 57-bit IOVA on platforms without CPU
> 5-level paging). However, current vIOMMU implementation still lacks logic to
> check against the physical IOMMU capability, future enhancements are expected
> to do this.
> Changes in V3: 
> - Address comments from Peter Xu: squash the 3rd patch in v2 into the 2nd
>   patch in this version.
> - Added "Reviewed-by: Peter Xu <address@hidden>"
> Changes in V2: 
> - Address comments from Peter Xu: add haw member in vtd_page_walk_info.
> - Address comments from Peter Xu: only searches for 4K/2M/1G mappings in
> iotlb are meaningful. 
> - Address comments from Peter Xu: cover letter changes(e.g. mention the test
> patch in kvm-unit-tests).
> - Coding style changes.
> ---
> Cc: "Michael S. Tsirkin" <address@hidden> 
> Cc: Igor Mammedov <address@hidden> 
> Cc: Marcel Apfelbaum <address@hidden>
> Cc: Paolo Bonzini <address@hidden> 
> Cc: Richard Henderson <address@hidden> 
> Cc: Eduardo Habkost <address@hidden>
> Cc: Peter Xu <address@hidden>

OK is this going anywhere?
How about dropping cpu flags probing for now, you can
always revisit it later.
Will make it maybe a bit less user friendly but OTOH

> ---
> Yu Zhang (2):
>   intel-iommu: differentiate host address width from IOVA address width.
>   intel-iommu: extend VTD emulation to allow 57-bit IOVA address width.
>  hw/i386/acpi-build.c           |  2 +-
>  hw/i386/intel_iommu.c          | 96 
> +++++++++++++++++++++++++++++-------------
>  hw/i386/intel_iommu_internal.h | 10 ++++-
>  include/hw/i386/intel_iommu.h  | 10 +++--
>  4 files changed, 81 insertions(+), 37 deletions(-)
> -- 
> 1.9.1

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