Linux Virtualization - Sep 2020 - [PATCH v12 1/2] virtio: let arch advertise guest's memory access restrictions

Hi all,

The goal of the series is to give a chance to the architecture
to validate VIRTIO device features.

I changed VIRTIO_F_IOMMU_PLATFORM to VIRTIO_F_ACCESS_PLATFORM
I forgot in drivers/virtio/Kconfig, and put back the inclusion
of virtio_config.h for the definition of the callback in
arch/s390/mm/init.c I wrongly removed in the last series.

Regards,
Pierre


Pierre Morel (2):
  virtio: let arch advertise guest's memory access restrictions
  s390: virtio: PV needs VIRTIO I/O device protection

 arch/s390/Kconfig             |  1 +
 arch/s390/mm/init.c           | 11 +++++++++++
 drivers/virtio/Kconfig        |  6 ++++++
 drivers/virtio/virtio.c       | 15 +++++++++++++++
 include/linux/virtio_config.h | 10 ++++++++++
 5 files changed, 43 insertions(+)

-- 
2.25.1

to v12
- replaced VIRTIO_F_IOMMU_PLATFORM with VIRTIO_F_ACCESS_PLATFORM
  in drivers/virtio/Kconfig
  (Halil)

- suppress inaccurate part of the comment in patch 2
  (Halil)

- added back virtio_config.h to define
  arch_has_restricted_virtio_memory_access
  (kernel robot)

to v11:
- replaced VIRTIO_F_IOMMU_PLATFORM with VIRTIO_F_ACCESS_PLATFORM

to v10:
- removed virtio_config.h unnecessary include
- wording
  (Connie)

to v9:

- move virtio tests back to virtio_finalize_features
  (Connie)

- remove virtio device argument

to v8:

- refactoring by using an optional callback
  (Connie)

to v7:

- typo in warning message
  (Connie)
to v6:

- rewording warning messages
  (Connie, Halil)

to v5:

- return directly from S390 arch_validate_virtio_features()
  when the guest is not protected.
  (Connie)

- Somme rewording
  (Connie, Michael)

- moved back code from arch/s390/ ...kernel/uv.c to ...mm/init.c
  (Christian)

to v4:

- separate virtio and arch code
  (Pierre)

- moved code from arch/s390/mm/init.c to arch/s390/kernel/uv.c
  (as interpreted from Heiko's comment)

- moved validation inside the arch code
  (Connie)

- moved the call to arch validation before VIRTIO_F_1 test
  (Michael)

to v3:

- add warning
  (Connie, Christian)

- add comment
  (Connie)

- change hook name
  (Halil, Connie)

to v2:

- put the test in virtio_finalize_features()
  (Connie)

- put the test inside VIRTIO core
  (Jason)

- pass a virtio device as parameter
  (Halil)

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 <pmorel at linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck at redhat.com>
Reviewed-by: Halil Pasic <pasic at linux.ibm.com>
---
 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

If protected virtualization is active on s390, VIRTIO has only retricted
access to the guest memory.
Define CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS and export
arch_has_restricted_virtio_memory_access to advertize VIRTIO if that's
the case.

Signed-off-by: Pierre Morel <pmorel at linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck at redhat.com>
Reviewed-by: Halil Pasic <pasic at linux.ibm.com>
---
 arch/s390/Kconfig   |  1 +
 arch/s390/mm/init.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b29fcc66ec39..938246200d39 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -820,6 +820,7 @@ menu "Virtualization"
 config PROTECTED_VIRTUALIZATION_GUEST
 	def_bool n
 	prompt "Protected virtualization guest support"
+	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
 	help
 	  Select this option, if you want to be able to run this
 	  kernel as a protected virtualization KVM guest.
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 0d282081dc1f..e27f050cb516 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -45,6 +45,7 @@
 #include <asm/kasan.h>
 #include <asm/dma-mapping.h>
 #include <asm/uv.h>
+#include <linux/virtio_config.h>
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
 
@@ -160,6 +161,16 @@ bool force_dma_unencrypted(struct device *dev)
 	return is_prot_virt_guest();
 }
 
+#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
+
+int arch_has_restricted_virtio_memory_access(void)
+{
+	return is_prot_virt_guest();
+}
+EXPORT_SYMBOL(arch_has_restricted_virtio_memory_access);
+
+#endif
+
 /* protected virtualization */
 static void pv_init(void)
 {
-- 
2.25.1

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 <pmorel at linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck at redhat.com>
> Reviewed-by: Halil Pasic <pasic at linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>

> ---
>  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 */
>

On 10.09.20 10:53, Pierre Morel wrote:
> If protected virtualization is active on s390, VIRTIO has only retricted
> access to the guest memory.
> Define CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS and export
> arch_has_restricted_virtio_memory_access to advertize VIRTIO if that's
> the case.
> 
> Signed-off-by: Pierre Morel <pmorel at linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck at redhat.com>
> Reviewed-by: Halil Pasic <pasic at linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>

Michael, I am fine if this patch goes via the virtio tree.

> ---
>  arch/s390/Kconfig   |  1 +
>  arch/s390/mm/init.c | 11 +++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index b29fcc66ec39..938246200d39 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -820,6 +820,7 @@ menu "Virtualization"
>  config PROTECTED_VIRTUALIZATION_GUEST
>  	def_bool n
>  	prompt "Protected virtualization guest support"
> +	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
>  	help
>  	  Select this option, if you want to be able to run this
>  	  kernel as a protected virtualization KVM guest.
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 0d282081dc1f..e27f050cb516 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -45,6 +45,7 @@
>  #include <asm/kasan.h>
>  #include <asm/dma-mapping.h>
>  #include <asm/uv.h>
> +#include <linux/virtio_config.h>
>  
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>  
> @@ -160,6 +161,16 @@ bool force_dma_unencrypted(struct device *dev)
>  	return is_prot_virt_guest();
>  }
>  
> +#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> +
> +int arch_has_restricted_virtio_memory_access(void)
> +{
> +	return is_prot_virt_guest();
> +}
> +EXPORT_SYMBOL(arch_has_restricted_virtio_memory_access);
> +
> +#endif
> +
>  /* protected virtualization */
>  static void pv_init(void)
>  {
>

Michael,

are you going to pick this series?


On 10.09.20 10:53, Pierre Morel wrote:
> Hi all,
> 
> The goal of the series is to give a chance to the architecture
> to validate VIRTIO device features.
> 
> I changed VIRTIO_F_IOMMU_PLATFORM to VIRTIO_F_ACCESS_PLATFORM
> I forgot in drivers/virtio/Kconfig, and put back the inclusion
> of virtio_config.h for the definition of the callback in
> arch/s390/mm/init.c I wrongly removed in the last series.
> 
> Regards,
> Pierre
> 
> 
> Pierre Morel (2):
>   virtio: let arch advertise guest's memory access restrictions
>   s390: virtio: PV needs VIRTIO I/O device protection
> 
>  arch/s390/Kconfig             |  1 +
>  arch/s390/mm/init.c           | 11 +++++++++++
>  drivers/virtio/Kconfig        |  6 ++++++
>  drivers/virtio/virtio.c       | 15 +++++++++++++++
>  include/linux/virtio_config.h | 10 ++++++++++
>  5 files changed, 43 insertions(+)
>

Will do for the next Linux.

On Tue, Sep 22, 2020 at 02:15:17PM +0200, Christian Borntraeger
wrote:
> Michael,
> 
> are you going to pick this series?
> 
> 
> On 10.09.20 10:53, Pierre Morel wrote:
> > Hi all,
> > 
> > The goal of the series is to give a chance to the architecture
> > to validate VIRTIO device features.
> > 
> > I changed VIRTIO_F_IOMMU_PLATFORM to VIRTIO_F_ACCESS_PLATFORM
> > I forgot in drivers/virtio/Kconfig, and put back the inclusion
> > of virtio_config.h for the definition of the callback in
> > arch/s390/mm/init.c I wrongly removed in the last series.
> > 
> > Regards,
> > Pierre
> > 
> > 
> > Pierre Morel (2):
> >   virtio: let arch advertise guest's memory access restrictions
> >   s390: virtio: PV needs VIRTIO I/O device protection
> > 
> >  arch/s390/Kconfig             |  1 +
> >  arch/s390/mm/init.c           | 11 +++++++++++
> >  drivers/virtio/Kconfig        |  6 ++++++
> >  drivers/virtio/virtio.c       | 15 +++++++++++++++
> >  include/linux/virtio_config.h | 10 ++++++++++
> >  5 files changed, 43 insertions(+)
> >