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Re: [Xen-devel] [PATCH V3 8/8] iommu/arm: Add Renesas IPMMU-VMSA support

  • To: Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
  • Date: Thu, 29 Aug 2019 08:37:16 +0000
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  • Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, "julien.grall@xxxxxxx" <julien.grall@xxxxxxx>, "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>, "Volodymyr_Babchuk@xxxxxxxx" <Volodymyr_Babchuk@xxxxxxxx>
  • Delivery-date: Thu, 29 Aug 2019 08:37:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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  • Thread-topic: [PATCH V3 8/8] iommu/arm: Add Renesas IPMMU-VMSA support

Hi Oleksandr-san,

> From: Oleksandr Tyshchenko, Sent: Wednesday, August 21, 2019 3:10 AM
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> The IPMMU-VMSA is VMSA-compatible I/O Memory Management Unit (IOMMU)
> which provides address translation and access protection functionalities
> to processing units and interconnect networks.
> Please note, current driver is supposed to work only with newest
> Gen3 SoCs revisions which IPMMU hardware supports stage 2 translation

This is still "Gen3", so that please replace it with "R-Car Gen3"...

> table format and is able to use CPU's P2M table as is if one is
> 3-level page table (up to 40 bit IPA).
> The major differences compare to the Linux driver are:
> 1. Stage 1/Stage 2 translation. Linux driver supports Stage 1
> translation only (with Stage 1 translation table format). It manages
> page table by itself. But Xen driver supports Stage 2 translation
> (with Stage 2 translation table format) to be able to share the P2M
> with the CPU. Stage 1 translation is always bypassed in Xen driver.
> So, Xen driver is supposed to be used with newest R-Car Gen3 SoC revisions
> only (H3 ES3.0, M3-W+, etc.) which IPMMU H/W supports stage 2 translation
> table format.
> 2. AArch64 support. Linux driver uses VMSAv8-32 mode, while Xen driver
> enables Armv8 VMSAv8-64 mode to cover up to 40 bit input address.
> 3. Context bank (sets of page table) usage. In Xen, each context bank is
> mapped to one Xen domain. So, all devices being pass throughed to the
> same Xen domain share the same context bank.
> 4. IPMMU device tracking. In Xen, all IOMMU devices are managed
> by single driver instance. So, driver uses global list to keep track
> of registered IPMMU devices.
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> CC: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>

About this hardware handling, this patch seems good to me. But, since
I'm not familiar about Xen passthrough framework, I think I cannot
add my Reviewed-by tag into this patch. What do you think?

Best regards,
Yoshihiro Shimoda

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