linux-kernel - Re: [PATCH v9 1/2] virtio: let arch advertise guest's memory access restrictions

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Message-ID: <20200821135906.1c6bede3.cohuck@redhat.com>
Date:   Fri, 21 Aug 2020 13:59:06 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, pasic@...ux.ibm.com,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, mst@...hat.com,
        jasowang@...hat.com, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, thomas.lendacky@....com,
        david@...son.dropbear.id.au, linuxram@...ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v9 1/2] virtio: let arch advertise guest's memory access
 restrictions

On Wed, 19 Aug 2020 18:23:17 +0200
Pierre Morel <pmorel@...ux.ibm.com> wrote:

> An architecture may restrict host access to guest memory.

"e.g. IBM s390 Secure Execution or AMD SEV"

Just to make clearer what you are referring to?

> 
> Provide a new Kconfig entry the architecture can select,
> CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS, when it provides
> the arch_has_restricted_virtio_memory_access callback to advertise

s/advertise/advertise to/

> VIRTIO common code when the architecture restricts memory access
> from the host.

"The common code can then fail the probe for any device where
VIRTIO_F_IOMMU_PLATFORM is required, but not set."

?

> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>  drivers/virtio/Kconfig        |  6 ++++++
>  drivers/virtio/virtio.c       | 15 +++++++++++++++
>  include/linux/virtio_config.h |  9 +++++++++
>  3 files changed, 30 insertions(+)
> 
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 5809e5f5b157..509f3b4d8ba1 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -6,6 +6,12 @@ config VIRTIO
>  	  bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
>  	  or CONFIG_S390_GUEST.
>  
> +config ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> +	bool
> +	help
> +	  This option is selected by any architecture enforcing
> +	  VIRTIO_F_IOMMU_PLATFORM

"This option is selected if the architecture may need to enforce
VIRTIO_F_IOMMU_PLATFORM."

?

> +
>  menuconfig VIRTIO_MENU
>  	bool "Virtio drivers"
>  	default y

(...)

Reviewed-by: Cornelia Huck <cohuck@...hat.com>