Re: [PATCH v4 2/2] s390: virtio: PV needs VIRTIO I/O device protection
From: Cornelia Huck <cohuck@redhat.com>
Date: 2020-07-07 09:46:52
Also in:
kvm, linux-s390, lkml
On Tue, 7 Jul 2020 10:44:37 +0200 Pierre Morel [off-list ref] wrote:
S390, protecting the guest memory against unauthorized host access needs to enforce VIRTIO I/O device protection through the use of VIRTIO_F_VERSION_1 and VIRTIO_F_IOMMU_PLATFORM.
Hm... what about: "If protected virtualization is active on s390, the virtio queues are not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been negotiated. Use the new arch_validate_virtio_features() interface to enforce this."
quoted hunk ↗ jump to hunk
Signed-off-by: Pierre Morel <redacted> --- arch/s390/kernel/uv.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index c296e5c8dbf9..106330f6eda1 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c@@ -14,6 +14,7 @@ #include <linux/memblock.h> #include <linux/pagemap.h> #include <linux/swap.h> +#include <linux/virtio_config.h> #include <asm/facility.h> #include <asm/sections.h> #include <asm/uv.h>@@ -413,3 +414,27 @@ static int __init uv_info_init(void) } device_initcall(uv_info_init); #endif + +/* + * arch_validate_virtio_iommu_platform
s/arch_validate_virtio_iommu_platform/arch_validate_virtio_features/
+ * @dev: the VIRTIO device being added + * + * Return value: returns -ENODEV if any features of the + * device breaks the protected virtualization + * 0 otherwise.
I don't think you need to specify the contract here: that belongs to the definition in the virtio core. What about simply adding a sentence "Return an error if required features are missing on a guest running with protected virtualization." ?
+ */
+int arch_validate_virtio_features(struct virtio_device *dev)
+{Maybe jump out immediately if the guest is not protected?
+ if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
+ dev_warn(&dev->dev, "device must provide VIRTIO_F_VERSION_1\n");
+ return is_prot_virt_guest() ? -ENODEV : 0;
+ }
+
+ if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
+ dev_warn(&dev->dev,
+ "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
+ return is_prot_virt_guest() ? -ENODEV : 0;
+ }
if (!is_prot_virt_guest())
return 0;
if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
dev_warn(&dev->dev,
"legacy virtio is incompatible with protected guests");
return -ENODEV;
}
if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
dev_warn(&dev->dev,
"device does not work with limited memory access in protected guests");
return -ENODEV;
}
+ + return 0; +}