KVM: Add documentation for Xen hypercall and shared_info updates

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e00a66d7237285a9716814d9cf791c06bceb94a7..d1c30105e6fd145b308e4c17b9695916104f3aba 100644 (file)
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -944,6 +944,13 @@ memory.
        __u8 pad2[30];
   };
 
+If the KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL flag is returned from the
+KVM_CAP_XEN_HVM check, it may be set in the flags field of this ioctl.
+This requests KVM to generate the contents of the hypercall page
+automatically, and also to intercept hypercalls with KVM_EXIT_XEN.
+In this case, all of the blob size and address fields must be zero.
+
+No other flags are currently valid.
 
 4.29 KVM_GET_CLOCK
 ------------------
@@ -4807,6 +4814,71 @@ into user space.
 If a vCPU is in running state while this ioctl is invoked, the vCPU may
 experience inconsistent filtering behavior on MSR accesses.
 
+4.127 KVM_XEN_HVM_SET_ATTR
+--------------------------
+
+:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_xen_hvm_attr
+:Returns: 0 on success, < 0 on error
+
+::
+
+  struct kvm_xen_hvm_attr {
+       __u16 type;
+
+       union {
+               __u8 long_mode;
+               struct {
+                       __u64 gfn;
+               } shared_info;
+               struct {
+                       __u32 vcpu_id;
+                       __u64 gpa;
+               } vcpu_attr;
+               __u64 pad[4];
+       } u;
+  };
+
+type values:
+
+KVM_XEN_ATTR_TYPE_LONG_MODE
+  Sets the ABI mode of the VM to 32-bit or 64-bit (long mode). This
+  determines the layout of the shared info pages exposed to the VM.
+
+KVM_XEN_ATTR_TYPE_SHARED_INFO
+  Sets the guest physical frame number at which the Xen "shared info"
+  page resides. Note that although Xen places vcpu_info for the first
+  32 vCPUs in the shared_info page, KVM does not automatically do so
+  and requires that KVM_XEN_ATTR_TYPE_VCPU_INFO be used explicitly
+  even when the vcpu_info for a given vCPU resides at the "default"
+  location in the shared_info page. This is because KVM is not aware
+  of the Xen CPU id which is used as the index into the vcpu_info[]
+  array, so cannot know the correct default location.
+
+KVM_XEN_ATTR_TYPE_VCPU_INFO
+  Sets the guest physical address of the vcpu_info for a given vCPU.
+
+KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO
+  Sets the guest physical address of an additional pvclock structure
+  for a given vCPU. This is typically used for guest vsyscall support.
+
+KVM_XEN_ATTR_TYPE_VCPU_RUNSTATE
+  Sets the guest physical address of the vcpu_runstate_info for a given
+  vCPU. This is how a Xen guest tracks CPU state such as steal time.
+
+4.128 KVM_XEN_HVM_GET_ATTR
+--------------------------
+
+:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_xen_hvm_attr
+:Returns: 0 on success, < 0 on error
+
+Allows Xen VM attributes to be read. For the structure and types,
+see KVM_XEN_HVM_SET_ATTR above.
 
 5. The kvm_run structure
 ========================
@@ -5303,6 +5375,34 @@ wants to write. Once finished processing the event, user space must continue
 vCPU execution. If the MSR write was unsuccessful, user space also sets the
 "error" field to "1".
 
+::
+
+
+               struct kvm_xen_exit {
+  #define KVM_EXIT_XEN_HCALL          1
+                       __u32 type;
+                       union {
+                               struct {
+                                       __u32 longmode;
+                                       __u32 cpl;
+                                       __u64 input;
+                                       __u64 result;
+                                       __u64 params[6];
+                               } hcall;
+                       } u;
+               };
+               /* KVM_EXIT_XEN */
+                struct kvm_hyperv_exit xen;
+
+Indicates that the VCPU exits into userspace to process some tasks
+related to Xen emulation.
+
+Valid values for 'type' are:
+
+  - KVM_EXIT_XEN_HCALL -- synchronously notify user-space about Xen hypercall.
+    Userspace is expected to place the hypercall result into the appropriate
+    field before invoking KVM_RUN again.
+
 ::
 
                /* Fix the size of the union. */
@@ -6390,3 +6490,26 @@ When enabled, KVM will disable paravirtual features provided to the
 guest according to the bits in the KVM_CPUID_FEATURES CPUID leaf
 (0x40000001). Otherwise, a guest may use the paravirtual features
 regardless of what has actually been exposed through the CPUID leaf.
+
+8.29 KVM_CAP_XEN_HVM
+--------------------
+
+:Architectures: x86
+
+This capability indicates the features that Xen supports for hosting Xen
+PVHVM guests. Valid flags are::
+
+  #define KVM_XEN_HVM_CONFIG_HYPERCALL_MSR     (1 << 0)
+  #define KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL   (1 << 1)
+  #define KVM_XEN_HVM_CONFIG_SHARED_INFO       (1 << 2)
+
+The KVM_XEN_HVM_CONFIG_HYPERCALL_MSR flag indicates that the KVM_XEN_HVM_CONFIG
+ioctl is available, for the guest to set its hypercall page.
+
+If KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL is also set, the same flag may also be
+provided in the flags to KVM_XEN_HVM_CONFIG, without providing hypercall page
+contents, to request that KVM generate hypercall page content automatically
+and also enable interception of guest hypercalls with KVM_EXIT_XEN.
+
+The KVM_XEN_HVM_CONFIG_SHARED_INFO flag indicates the availability of the
+KVM_XEN_HVM_SET_ATTR and KVM_XEN_HVM_GET_ATTR ioctls.