On 1/3/2024 6:32 AM, Maxim Levitsky wrote:
On Thu, 2023-12-21 at 09:02 -0500, Yang Weijiang wrote:
Define new fpu_guest_cfg to hold all guest FPU settings so that it can
differ from generic kernel FPU settings, e.g., enabling CET supervisor
xstate by default for guest fpstate while it's remained disabled in
kernel FPU config.
The kernel dynamic xfeatures are specifically used by guest fpstate now,
add the mask for guest fpstate so that guest_perm.__state_permit ==
(fpu_kernel_cfg.default_xfeature | XFEATURE_MASK_KERNEL_DYNAMIC). And
if guest fpstate is re-allocated to hold user dynamic xfeatures, the
resulting permissions are consumed before calculate new guest fpstate.
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/include/asm/fpu/types.h | 2 +-
arch/x86/kernel/fpu/core.c | 70 ++++++++++++++++++++++++++++++--
arch/x86/kernel/fpu/xstate.c | 10 +++++
3 files changed, 78 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index c6fd13a17205..306825ad6bc0 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -602,6 +602,6 @@ struct fpu_state_config {
};
/* FPU state configuration information */
-extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg;
+extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg, fpu_guest_cfg;
#endif /* _ASM_X86_FPU_H */
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index a21a4d0ecc34..976f519721e2 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -33,10 +33,67 @@ DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
DEFINE_PER_CPU(u64, xfd_state);
#endif
-/* The FPU state configuration data for kernel and user space */
+/* The FPU state configuration data for kernel, user space and guest. */
+/*
+ * kernel FPU config:
+ *
+ * all known and CPU supported user and supervisor features except
+ * - independent kernel features (XFEATURE_LBR)
+ * @fpu_kernel_cfg.max_features;
+ *
+ * all known and CPU supported user and supervisor features except
+ * - dynamic kernel features (CET_S)
+ * - independent kernel features (XFEATURE_LBR)
+ * - dynamic userspace features (AMX state)
+ * @fpu_kernel_cfg.default_features;
+ *
+ * size of compacted buffer with 'fpu_kernel_cfg.max_features'
+ * @fpu_kernel_cfg.max_size;
+ *
+ * size of compacted buffer with 'fpu_kernel_cfg.default_features'
+ * @fpu_kernel_cfg.default_size;
+ */
struct fpu_state_config fpu_kernel_cfg __ro_after_init;
+
+/*
+ * user FPU config:
+ *
+ * all known and CPU supported user features
+ * @fpu_user_cfg.max_features;
+ *
+ * all known and CPU supported user features except
+ * - dynamic userspace features (AMX state)
+ * @fpu_user_cfg.default_features;
+ *
+ * size of non-compacted buffer with 'fpu_user_cfg.max_features'
+ * @fpu_user_cfg.max_size;
+ *
+ * size of non-compacted buffer with 'fpu_user_cfg.default_features'
+ * @fpu_user_cfg.default_size;
+ */
struct fpu_state_config fpu_user_cfg __ro_after_init;
+/*
+ * guest FPU config:
+ *
+ * all known and CPU supported user and supervisor features except
+ * - independent kernel features (XFEATURE_LBR)
+ * @fpu_guest_cfg.max_features;
+ *
+ * all known and CPU supported user and supervisor features except
+ * - independent kernel features (XFEATURE_LBR)
+ * - dynamic userspace features (AMX state)
+ * @fpu_guest_cfg.default_features;
+ *
+ * size of compacted buffer with 'fpu_guest_cfg.max_features'
+ * @fpu_guest_cfg.max_size;
+ *
+ * size of compacted buffer with 'fpu_guest_cfg.default_features'
+ * @fpu_guest_cfg.default_size;
+ */
IMHO this comment is too verbose. I didn't intend it to be copied verbatim,
to the kernel, but rather to explain the meaning of the fpu context fields
to both of us (I also keep on forgetting what each combination means...).
At least this comment should not include examples because xfeatures
are subject to change.
Yeah, I cannot find a better place to put these annotations, but feel putting them here
is not too bad :-). How about putting them in commit log?
the examples inlined are just to make it clearer for audiences how the fields are used, surely
will remove them later.
