mshv: Extend create partition ioctl to support cpu features

The existing mshv create partition ioctl does not provide a way to
specify which cpu features are enabled in the guest. Instead, it
attempts to enable all features and those that are not supported are
silently disabled by the hypervisor.

This was done to reduce unnecessary complexity and is sufficient for
many cases. However, new scenarios require fine-grained control over
these features.

Define a new mshv_create_partition_v2 structure which supports
passing the disabled processor and xsave feature bits through to the
create partition hypercall directly.

Introduce a new flag MSHV_PT_BIT_CPU_AND_XSAVE_FEATURES which enables
the new structure. If unset, the original mshv_create_partition struct
is used, with the old behavior of enabling all features.

Co-developed-by: Jinank Jain <jinankjain@microsoft.com>
Signed-off-by: Jinank Jain <jinankjain@microsoft.com>
Signed-off-by: Muminul Islam <muislam@microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
index 374f75e198bc..b645d17cc531 100644
--- a/include/uapi/linux/mshv.h
+++ b/include/uapi/linux/mshv.h
@@ -26,6 +26,7 @@ enum {
 	MSHV_PT_BIT_LAPIC,
 	MSHV_PT_BIT_X2APIC,
 	MSHV_PT_BIT_GPA_SUPER_PAGES,
+	MSHV_PT_BIT_CPU_AND_XSAVE_FEATURES,
 	MSHV_PT_BIT_COUNT,
 };
 
@@ -41,6 +42,8 @@ enum {
  * @pt_flags: Bitmask of 1 << MSHV_PT_BIT_*
  * @pt_isolation: MSHV_PT_ISOLATION_*
  *
+ * This is the initial/v1 version for backward compatibility.
+ *
  * Returns a file descriptor to act as a handle to a guest partition.
  * At this point the partition is not yet initialized in the hypervisor.
  * Some operations must be done with the partition in this state, e.g. setting
@@ -52,6 +55,37 @@ struct mshv_create_partition {
 	__u64 pt_isolation;
 };
 
+#define MSHV_NUM_CPU_FEATURES_BANKS 2
+
+/**
+ * struct mshv_create_partition_v2
+ *
+ * This is extended version of the above initial MSHV_CREATE_PARTITION
+ * ioctl and allows for following additional parameters:
+ *
+ * @pt_num_cpu_fbanks: Must be set to MSHV_NUM_CPU_FEATURES_BANKS.
+ * @pt_cpu_fbanks: Disabled processor feature banks array.
+ * @pt_disabled_xsave: Disabled xsave feature bits.
+ *
+ * pt_cpu_fbanks and pt_disabled_xsave are passed through as-is to the create
+ * partition hypercall.
+ *
+ * Returns : same as above original mshv_create_partition
+ */
+struct mshv_create_partition_v2 {
+	__u64 pt_flags;
+	__u64 pt_isolation;
+	__u16 pt_num_cpu_fbanks;
+	__u8  pt_rsvd[6];		/* MBZ */
+	__u64 pt_cpu_fbanks[MSHV_NUM_CPU_FEATURES_BANKS];
+	__u64 pt_rsvd1[2];		/* MBZ */
+#if defined(__x86_64__)
+	__u64 pt_disabled_xsave;
+#else
+	__u64 pt_rsvd2;			/* MBZ */
+#endif
+} __packed;
+
 /* /dev/mshv */
 #define MSHV_CREATE_PARTITION	_IOW(MSHV_IOCTL, 0x00, struct mshv_create_partition)