diff mbox series

[v6,19/19] KVM: Add documentation for Xen hypercall and shared_info updates

Message ID 20210203150114.920335-20-dwmw2@infradead.org (mailing list archive)
State New, archived
Headers show
Series KVM: Add minimal support for Xen HVM guests | expand

Commit Message

David Woodhouse Feb. 3, 2021, 3:01 p.m. UTC 
From: David Woodhouse <dwmw@amazon.co.uk>

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 Documentation/virt/kvm/api.rst | 170 ++++++++++++++++++++++++++++++++-
 1 file changed, 165 insertions(+), 5 deletions(-)

Comments

Paolo Bonzini Feb. 3, 2021, 4:17 p.m. UTC | #1 
On 03/02/21 16:01, David Woodhouse wrote:
> +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 in the struct kvm_xen_hvm_config.

Slight rewording:

  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.
+automatically; hypercalls will be intercepted and passed to userspace
+through KVM_EXIT_XEN.  In this case, all of the blob size and address
+fields must be zero.

  No other flags are currently valid in the struct kvm_xen_hvm_config.


Paolo

>   4.29 KVM_GET_CLOCK
>   ------------------
> @@ -4831,6 +4838,101 @@ 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;
> +	__u16 pad[3];
> +	union {
> +		__u8 long_mode;
> +		__u8 vector;
> +		struct {
> +			__u64 gfn;
> +		} shared_info;
> +		__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 instead requires that KVM_XEN_VCPU_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_UPCALL_VECTOR
> +  Sets the exception vector used to deliver Xen event channel upcalls.
> +
> +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.
> +
> +4.129 KVM_XEN_VCPU_SET_ATTR
> +---------------------------
> +
> +:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
> +:Architectures: x86
> +:Type: vcpu ioctl
> +:Parameters: struct kvm_xen_vcpu_attr
> +:Returns: 0 on success, < 0 on error
> +
> +::
> +
> +  struct kvm_xen_vcpu_attr {
> +	__u16 type;
> +	__u16 pad[3];
> +	union {
> +		__u64 gpa;
> +		__u64 pad[4];
> +	} u;
> +  };
> +
> +type values:
> +
> +KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO
> +  Sets the guest physical address of the vcpu_info for a given vCPU.
> +
> +KVM_XEN_VCPU_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.
> +
> +4.130 KVM_XEN_VCPU_GET_ATTR
> +--------------------------
> +
> +:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
> +:Architectures: x86
> +:Type: vcpu ioctl
> +:Parameters: struct kvm_xen_vcpu_attr
> +:Returns: 0 on success, < 0 on error
> +
> +Allows Xen vCPU attributes to be read. For the structure and types,
> +see KVM_XEN_VCPU_SET_ATTR above.
>   
>   5. The kvm_run structure
>   ========================
> @@ -4996,13 +5098,18 @@ to the byte array.
>   
>   .. note::
>   
> -      For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR,
> +      For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR, KVM_EXIT_XEN,
>         KVM_EXIT_EPR, KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR the corresponding
>         operations are complete (and guest state is consistent) only after userspace
>         has re-entered the kernel with KVM_RUN.  The kernel side will first finish
> -      incomplete operations and then check for pending signals.  Userspace
> -      can re-enter the guest with an unmasked signal pending to complete
> -      pending operations.
> +      incomplete operations and then check for pending signals.
> +
> +      The pending state of the operation is not preserved in state which is
> +      visible to userspace, thus userspace should ensure that the operation is
> +      completed before performing a live migration.  Userspace can re-enter the
> +      guest with an unmasked signal pending or with the immediate_exit field set
> +      to complete pending operations without allowing any further instructions
> +      to be executed.
>   
>   ::
>   
> @@ -5327,6 +5434,34 @@ 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. */
> @@ -6415,7 +6550,6 @@ 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_DIRTY_LOG_RING
>   ---------------------------
>   
> @@ -6502,3 +6636,29 @@ KVM_GET_DIRTY_LOG and KVM_CLEAR_DIRTY_LOG.  After enabling
>   KVM_CAP_DIRTY_LOG_RING with an acceptable dirty ring size, the virtual
>   machine will switch to ring-buffer dirty page tracking and further
>   KVM_GET_DIRTY_LOG or KVM_CLEAR_DIRTY_LOG ioctls will fail.
> +
> +8.30 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, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
> +KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
> +for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
> +vcpu_info is set.
>
diff mbox series

Patch

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 99ceb978c8b0..9c454c5b785c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -960,6 +960,13 @@  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 in the struct kvm_xen_hvm_config.
 
 4.29 KVM_GET_CLOCK
 ------------------
@@ -4831,6 +4838,101 @@  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;
+	__u16 pad[3];
+	union {
+		__u8 long_mode;
+		__u8 vector;
+		struct {
+			__u64 gfn;
+		} shared_info;
+		__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 instead requires that KVM_XEN_VCPU_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_UPCALL_VECTOR
+  Sets the exception vector used to deliver Xen event channel upcalls.
+
+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.
+
+4.129 KVM_XEN_VCPU_SET_ATTR
+---------------------------
+
+:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xen_vcpu_attr
+:Returns: 0 on success, < 0 on error
+
+::
+
+  struct kvm_xen_vcpu_attr {
+	__u16 type;
+	__u16 pad[3];
+	union {
+		__u64 gpa;
+		__u64 pad[4];
+	} u;
+  };
+
+type values:
+
+KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO
+  Sets the guest physical address of the vcpu_info for a given vCPU.
+
+KVM_XEN_VCPU_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.
+
+4.130 KVM_XEN_VCPU_GET_ATTR
+--------------------------
+
+:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xen_vcpu_attr
+:Returns: 0 on success, < 0 on error
+
+Allows Xen vCPU attributes to be read. For the structure and types,
+see KVM_XEN_VCPU_SET_ATTR above.
 
 5. The kvm_run structure
 ========================
@@ -4996,13 +5098,18 @@  to the byte array.
 
 .. note::
 
-      For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR,
+      For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR, KVM_EXIT_XEN,
       KVM_EXIT_EPR, KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR the corresponding
       operations are complete (and guest state is consistent) only after userspace
       has re-entered the kernel with KVM_RUN.  The kernel side will first finish
-      incomplete operations and then check for pending signals.  Userspace
-      can re-enter the guest with an unmasked signal pending to complete
-      pending operations.
+      incomplete operations and then check for pending signals.
+
+      The pending state of the operation is not preserved in state which is
+      visible to userspace, thus userspace should ensure that the operation is
+      completed before performing a live migration.  Userspace can re-enter the
+      guest with an unmasked signal pending or with the immediate_exit field set
+      to complete pending operations without allowing any further instructions
+      to be executed.
 
 ::
 
@@ -5327,6 +5434,34 @@  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. */
@@ -6415,7 +6550,6 @@  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_DIRTY_LOG_RING
 ---------------------------
 
@@ -6502,3 +6636,29 @@  KVM_GET_DIRTY_LOG and KVM_CLEAR_DIRTY_LOG.  After enabling
 KVM_CAP_DIRTY_LOG_RING with an acceptable dirty ring size, the virtual
 machine will switch to ring-buffer dirty page tracking and further
 KVM_GET_DIRTY_LOG or KVM_CLEAR_DIRTY_LOG ioctls will fail.
+
+8.30 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, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
+KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
+for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
+vcpu_info is set.