2020-08-18 15:02:36

by Pierre Morel

Subject: [PATCH v8 2/2] s390: virtio: PV needs VIRTIO I/O device protection

If protected virtualization is active on s390, the virtio queues are
not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been
negotiated.
Define CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS and export
arch_has_restricted_memory_access to fail probe if that's
not the case, preventing a host error on access attempt.

Signed-off-by: Pierre Morel <[email protected]>
---
arch/s390/Kconfig | 1 +
arch/s390/mm/init.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 31 insertions(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9cfd8de907cb..d4a3ef4fa27b 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_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 6dc7c3b60ef6..aec04d7dd089 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);

@@ -161,6 +162,35 @@ bool force_dma_unencrypted(struct device *dev)
return is_prot_virt_guest();
}

+#ifdef CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS
+/*
+ * arch_has_restricted_memory_access
+ * @dev: the VIRTIO device being added
+ *
+ * Return an error if required features are missing on a guest running
+ * with protected virtualization.
+ */
+int arch_has_restricted_memory_access(struct virtio_device *dev)
+{
+ if (!is_prot_virt_guest())
+ return 0;
+
+ 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_IOMMU_PLATFORM)) {
+ dev_warn(&dev->dev,
+ "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
+ return -ENODEV;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(arch_has_restricted_memory_access);
+#endif
+
/* protected virtualization */
static void pv_init(void)
{
--
2.25.1

2020-08-18 17:23:52

by Cornelia Huck

Subject: Re: [PATCH v8 2/2] s390: virtio: PV needs VIRTIO I/O device protection

On Tue, 18 Aug 2020 16:58:31 +0200
Pierre Morel <[email protected]> wrote:

> If protected virtualization is active on s390, the virtio queues are
> not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been
> negotiated.
> Define CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS and export
> arch_has_restricted_memory_access to fail probe if that's
> not the case, preventing a host error on access attempt.
>
> Signed-off-by: Pierre Morel <[email protected]>
> ---
> arch/s390/Kconfig | 1 +
> arch/s390/mm/init.c | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 9cfd8de907cb..d4a3ef4fa27b 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_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 6dc7c3b60ef6..aec04d7dd089 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);
>
> @@ -161,6 +162,35 @@ bool force_dma_unencrypted(struct device *dev)
> return is_prot_virt_guest();
> }
>
> +#ifdef CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS
> +/*
> + * arch_has_restricted_memory_access
> + * @dev: the VIRTIO device being added
> + *
> + * Return an error if required features are missing on a guest running
> + * with protected virtualization.
> + */
> +int arch_has_restricted_memory_access(struct virtio_device *dev)
> +{
> + if (!is_prot_virt_guest())
> + return 0;

If you just did a

return is_prot_virt_guest();

and did the virtio feature stuff in the virtio core, this function
would be short and sweet :)

> +
> + 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_IOMMU_PLATFORM)) {
> + dev_warn(&dev->dev,
> + "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(arch_has_restricted_memory_access);
> +#endif
> +
> /* protected virtualization */
> static void pv_init(void)
> {

2020-08-19 08:54:25

by Pierre Morel

Subject: Re: [PATCH v8 2/2] s390: virtio: PV needs VIRTIO I/O device protection

On 2020-08-18 19:22, Cornelia Huck wrote:

>> + */
>> +int arch_has_restricted_memory_access(struct virtio_device *dev)
>> +{
>> + if (!is_prot_virt_guest())
>> + return 0;
>
> If you just did a
>
> return is_prot_virt_guest();
>
> and did the virtio feature stuff in the virtio core, this function
> would be short and sweet :)


yes, the smaller the better, thanks

Pierre

--
Pierre Morel
IBM Lab Boeblingen