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Subject: Re: [PATCH v3 0/3] virtio: support requiring restricted access per
 device
To:     Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org,
        x86@kernel.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-arch@vger.kernel.org
Cc:     Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Russell King <linux@armlinux.org.uk>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        linux-arm-kernel@lists.infradead.org
References: <20220622063838.8854-1-jgross@suse.com>
From:   Oleksandr <olekstysh@gmail.com>
Message-ID: <7eb66aec-df40-4e12-8211-8a6db4ad6060@gmail.com>
Date:   Wed, 22 Jun 2022 13:20:30 +0300
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On 22.06.22 09:38, Juergen Gross wrote:

Hello Juergen

> Instead of an all or nothing approach add support for requiring
> restricted memory access per device.
>
> Changes in V3:
> - new patches 1 + 2
> - basically complete rework of patch 3
>
> Juergen Gross (3):
>    virtio: replace restricted mem access flag with callback
>    kernel: remove platform_has() infrastructure
>    xen: don't require virtio with grants for non-PV guests
>
>   MAINTAINERS                            |  8 --------
>   arch/arm/xen/enlighten.c               |  4 +++-
>   arch/s390/mm/init.c                    |  4 ++--
>   arch/x86/mm/mem_encrypt_amd.c          |  4 ++--
>   arch/x86/xen/enlighten_hvm.c           |  4 +++-
>   arch/x86/xen/enlighten_pv.c            |  5 ++++-
>   drivers/virtio/Kconfig                 |  4 ++++
>   drivers/virtio/Makefile                |  1 +
>   drivers/virtio/virtio.c                |  4 ++--
>   drivers/virtio/virtio_anchor.c         | 18 +++++++++++++++++
>   drivers/xen/Kconfig                    |  9 +++++++++
>   drivers/xen/grant-dma-ops.c            | 10 ++++++++++
>   include/asm-generic/Kbuild             |  1 -
>   include/asm-generic/platform-feature.h |  8 --------
>   include/linux/platform-feature.h       | 19 ------------------
>   include/linux/virtio_anchor.h          | 19 ++++++++++++++++++
>   include/xen/xen-ops.h                  |  6 ++++++
>   include/xen/xen.h                      |  8 --------
>   kernel/Makefile                        |  2 +-
>   kernel/platform-feature.c              | 27 --------------------------
>   20 files changed, 84 insertions(+), 81 deletions(-)
>   create mode 100644 drivers/virtio/virtio_anchor.c
>   delete mode 100644 include/asm-generic/platform-feature.h
>   delete mode 100644 include/linux/platform-feature.h
>   create mode 100644 include/linux/virtio_anchor.h
>   delete mode 100644 kernel/platform-feature.c

I have tested the series on Arm64 guest using Xen hypervisor and didn't 
notice any issues.


I assigned two virtio-mmio devices to the guest:
#1 - grant dma device (required DT binding is present, so 
xen_is_grant_dma_device() returns true), virtio-mmio modern transport 
(backend offers VIRTIO_F_VERSION_1, VIRTIO_F_ACCESS_PLATFORM)
#2 - non grant dma device (required DT binding is absent, so 
xen_is_grant_dma_device() returns false), virtio-mmio legacy transport 
(backend does not offer these flags)


# CONFIG_XEN_VIRTIO is not set

both works, and both do not use grant mappings for virtio


CONFIG_XEN_VIRTIO=y
# CONFIG_XEN_VIRTIO_FORCE_GRANT is not set

both works, #1 uses grant mappings for virtio, #2 does not use it


CONFIG_XEN_VIRTIO=y
CONFIG_XEN_VIRTIO_FORCE_GRANT=y

only #1 works and uses grant mappings for virtio, #2 was rejected by 
validation in virtio_features_ok()


You can add my:
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 
guest using Xen


>
-- 
Regards,

Oleksandr Tyshchenko