From: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Define a new XFEATURE_MASK_SUPERVISOR_GUEST mask to specify the features
that are enabled by default in guest FPUs but not in host FPUs.
Add CET_KERNEL as the first guest-only feature to save host FPUs from
allocating XSAVE buffer space for all threads on CET-capable parts.
Co-developed-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
Dropped Dave's Suggested-by as the patch has been changed significantly
---
arch/x86/include/asm/fpu/types.h | 9 +++++----
arch/x86/include/asm/fpu/xstate.h | 3 +++
arch/x86/kernel/fpu/xstate.c | 5 ++++-
3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 80647c060b32..079f3241e25b 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -568,8 +568,9 @@ struct fpu_state_config {
* @default_size:
*
* The default size of the register state buffer. Includes all
- * supported features except independent managed features and
- * features which have to be requested by user space before usage.
+ * supported features except independent managed features,
+ * guest-only features and features which have to be requested by
+ * user space before usage.
*/
unsigned int default_size;
@@ -595,8 +596,8 @@ struct fpu_state_config {
* @default_features:
*
* The default supported features bitmap. Does not include
- * independent managed features and features which have to
- * be requested by user space before usage.
+ * independent managed features, guest-only features and features
+ * which have to be requested by user space before usage.
*/
u64 default_features;
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 8990cf381bef..69db17476061 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -45,6 +45,9 @@
/* Features which are dynamically enabled for a process on request */
#define XFEATURE_MASK_USER_DYNAMIC XFEATURE_MASK_XTILE_DATA
+/* Supervisor features which are enabled only in guest FPUs */
+#define XFEATURE_MASK_SUPERVISOR_GUEST XFEATURE_MASK_CET_KERNEL
+
/* All currently supported supervisor features */
#define XFEATURE_MASK_SUPERVISOR_SUPPORTED (XFEATURE_MASK_PASID | \
XFEATURE_MASK_CET_USER | \
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 1dd6ddba8723..b19960215074 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -55,7 +55,7 @@ static const char *xfeature_names[] =
"Protection Keys User registers",
"PASID state",
"Control-flow User registers",
- "Control-flow Kernel registers",
+ "Control-flow Kernel registers (KVM only)",
"unknown xstate feature",
"unknown xstate feature",
"unknown xstate feature",
@@ -813,6 +813,9 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
fpu_kernel_cfg.guest_default_features = fpu_kernel_cfg.default_features;
+ /* Clean out guest-only features from default */
+ fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_SUPERVISOR_GUEST;
+
fpu_user_cfg.default_features = fpu_user_cfg.max_features;
fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
fpu_user_cfg.guest_default_features = fpu_user_cfg.default_features;
--
2.46.1
