2020-09-10 08:55:43

by Pierre Morel

Subject: [PATCH v12 1/2] virtio: let arch advertise guest's memory access restrictions

An architecture may restrict host access to guest memory,
e.g. IBM s390 Secure Execution or AMD SEV.

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
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_ACCESS_PLATFORM is required, but not set.

Signed-off-by: Pierre Morel <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Reviewed-by: Halil Pasic <[email protected]>
---
drivers/virtio/Kconfig | 6 ++++++
drivers/virtio/virtio.c | 15 +++++++++++++++
include/linux/virtio_config.h | 10 ++++++++++
3 files changed, 31 insertions(+)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 5c92e4a50882..ef2d49430800 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 if the architecture may need to enforce
+ VIRTIO_F_ACCESS_PLATFORM
+
menuconfig VIRTIO_MENU
bool "Virtio drivers"
default y
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a977e32a88f2..a2b3f12e10a2 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -176,6 +176,21 @@ int virtio_finalize_features(struct virtio_device *dev)
if (ret)
return ret;

+ ret = arch_has_restricted_virtio_memory_access();
+ if (ret) {
+ if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
+ dev_warn(&dev->dev,
+ "device must provide VIRTIO_F_VERSION_1\n");
+ return -ENODEV;
+ }
+
+ if (!virtio_has_feature(dev, VIRTIO_F_ACCESS_PLATFORM)) {
+ dev_warn(&dev->dev,
+ "device must provide VIRTIO_F_ACCESS_PLATFORM\n");
+ return -ENODEV;
+ }
+ }
+
if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
return 0;

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 8fe857e27ef3..3f697c8c8205 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -540,4 +540,14 @@ static inline void virtio_cwrite64(struct virtio_device *vdev,
virtio_cread_le((vdev), structname, member, ptr); \
_r; \
})
+
+#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
+int arch_has_restricted_virtio_memory_access(void);
+#else
+static inline int arch_has_restricted_virtio_memory_access(void)
+{
+ return 0;
+}
+#endif /* CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS */
+
#endif /* _LINUX_VIRTIO_CONFIG_H */
--
2.25.1

2020-09-10 09:10:38

by Christian Borntraeger

Subject: Re: [PATCH v12 1/2] virtio: let arch advertise guest's memory access restrictions

On 10.09.20 10:53, Pierre Morel wrote:
> An architecture may restrict host access to guest memory,
> e.g. IBM s390 Secure Execution or AMD SEV.
>
> 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
> 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_ACCESS_PLATFORM is required, but not set.
>
> Signed-off-by: Pierre Morel <[email protected]>
> Reviewed-by: Cornelia Huck <[email protected]>
> Reviewed-by: Halil Pasic <[email protected]>

Acked-by: Christian Borntraeger <[email protected]>


> ---
> drivers/virtio/Kconfig | 6 ++++++
> drivers/virtio/virtio.c | 15 +++++++++++++++
> include/linux/virtio_config.h | 10 ++++++++++
> 3 files changed, 31 insertions(+)
>
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 5c92e4a50882..ef2d49430800 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 if the architecture may need to enforce
> + VIRTIO_F_ACCESS_PLATFORM
> +
> menuconfig VIRTIO_MENU
> bool "Virtio drivers"
> default y
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index a977e32a88f2..a2b3f12e10a2 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -176,6 +176,21 @@ int virtio_finalize_features(struct virtio_device *dev)
> if (ret)
> return ret;
>
> + ret = arch_has_restricted_virtio_memory_access();
> + if (ret) {
> + if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
> + dev_warn(&dev->dev,
> + "device must provide VIRTIO_F_VERSION_1\n");
> + return -ENODEV;
> + }
> +
> + if (!virtio_has_feature(dev, VIRTIO_F_ACCESS_PLATFORM)) {
> + dev_warn(&dev->dev,
> + "device must provide VIRTIO_F_ACCESS_PLATFORM\n");
> + return -ENODEV;
> + }
> + }
> +
> if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> return 0;
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 8fe857e27ef3..3f697c8c8205 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -540,4 +540,14 @@ static inline void virtio_cwrite64(struct virtio_device *vdev,
> virtio_cread_le((vdev), structname, member, ptr); \
> _r; \
> })
> +
> +#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> +int arch_has_restricted_virtio_memory_access(void);
> +#else
> +static inline int arch_has_restricted_virtio_memory_access(void)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS */
> +
> #endif /* _LINUX_VIRTIO_CONFIG_H */
>