Re: [Qemu-devel] [RFC PATCH 0/9] ISA 3.00 KVM guest support

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Feb 07, 2017 at 01:56:43PM +1100, Sam Bobroff wrote:
> 
> Because KVM will soon provide the necessary infrastructure for KVM guests to
> run on POWER9 CPUs, we can now start exploiting this new functionality from
> QEMU. See:
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-January/153433.html
> 
> This work is not yet complete but it is functional and is presented for early
> review. It overlaps in some places with current work supporting the same guests
> under full emulation.
> 
> This set aims to support only the following scenarios:
> * A POWER9 host running in radix mode, running a guest in radix mode.
> * A POWER9 host running in hash mode, running a guest in hash mode.
> * A POWER9 host running in hash mode, running a guest in legacy(+) mode.
> (+) Where legacy means that the guest does not support ISA 3.00.
> 
> Hash or radix mode for the host is controlled via the "disable_radix" kernel
> command line parameter: the host will use radix unless disable_radix is given.
> For the guest it should be automatically selected to match the host.
> 
> Bad legacy guests: There are some recent kernels (e.g. 4.9) that will, when run
> as a KVM guest and if the ibm,pa-features entry in the device tree has the
> Radix MMU bit set, attempt to initialize the MMU as if they were a host (which
> will cause them to crash). To avoid exposing this problem, the Radix MMU bit
> is removed from ibm,pa-features when a legacy guest is detected.
> 
> Prerequsites:
> * This set is based on current QEMU master, but relies on some work already posted here:
> https://lists.gnu.org/archive/html/qemu-devel/2017-01/msg02527.html
> Specifically patches 1..4 which set up the new CPU and MMU models.

Ok, I've merged 1/9 and reviewed the rest.

> Notes:
>     * Migration/snapshots are not yet investigated.

So, it's reasonable to avoid migration for now.  I'm even ok merging
something without migration support *IF* it isn't a silent failure:
i.e. it must have at least a stub that will fail the migration early
if it's in a mode that's not supported.

>     * If the host cannot support the guest (e.g. radix host and a legacy guest)
>       then the guest will crash but QEMU should probably terminate with a
>       descriptive message.

Uh, yes, that would certainly be better.
> 
> 
> Sam Bobroff (9):
>   spapr: fix off-by-one error in spapr_ovec_populate_dt()
>   Update headers using update-linux-headers.sh
>   spapr: Add ibm,processor-radix-AP-encodings to the device tree
>   target-ppc: support KVM_CAP_PPC_MMU_RADIX, KVM_CAP_PPC_MMU_HASH_V3
>   spapr: Only setup HTP if necessary.
>   spapr: Add h_register_process_table() hypercall
>   spapr: Set ISA 3.00 radix and hash bits in OV5
>   spapr: Advertise ISA 3.0 MMU features in pa_features
>   spapr: Small cleanup of PPC MMU enums
> 
>  hw/ppc/spapr.c                                     | 152 +++++---
>  hw/ppc/spapr_hcall.c                               |  52 ++-
>  hw/ppc/spapr_ovec.c                                |   2 +-
>  include/hw/ppc/spapr.h                             |   4 +-
>  include/hw/ppc/spapr_ovec.h                        |   6 +
>  include/standard-headers/linux/input-event-codes.h |   2 +-
>  include/standard-headers/linux/pci_regs.h          |   8 +
>  include/standard-headers/linux/virtio_ids.h        |   1 +
>  linux-headers/asm-arm/kvm.h                        |   2 +
>  linux-headers/asm-arm/unistd.h                     | 419 +--------------------
>  linux-headers/asm-powerpc/kvm.h                    |  25 ++
>  linux-headers/asm-powerpc/unistd.h                 |   1 +
>  linux-headers/asm-x86/kvm_para.h                   |   4 +-
>  linux-headers/linux/kvm.h                          |  11 +-
>  linux-headers/linux/vfio.h                         |  10 +
>  target/ppc/cpu-qom.h                               |  12 +-
>  target/ppc/cpu.h                                   |   5 +
>  target/ppc/kvm.c                                   |  66 +++-
>  target/ppc/kvm_ppc.h                               |  13 +
>  target/ppc/mmu-hash64.c                            |  10 +-
>  target/ppc/mmu_helper.c                            |  67 ++--
>  target/ppc/translate.c                             |  12 +-
>  22 files changed, 346 insertions(+), 538 deletions(-)
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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