The following commit has been merged into the perf/core branch of tip:
Commit-ID: 50f408d96d4d1a945d2c50c5fd8ed400883edf0e
Gitweb: https://git.kernel.org/tip/50f408d96d4d1a945d2c50c5fd8ed400883edf0e
Author: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 03 Jul 2020 05:49:27 -07:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 08 Jul 2020 11:38:56 +02:00
x86/fpu/xstate: Add helpers for LBR dynamic supervisor feature
The perf subsystem will only need to save/restore the LBR state.
However, the existing helpers save all supported supervisor states to a
kernel buffer, which will be unnecessary. Two helpers are introduced to
only save/restore requested dynamic supervisor states. The supervisor
features in XFEATURE_MASK_SUPERVISOR_SUPPORTED and
XFEATURE_MASK_SUPERVISOR_UNSUPPORTED mask cannot be saved/restored using
these helpers.
The helpers will be used in the following patch.
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx>
Link: https://lkml.kernel.org/r/1593780569-62993-22-git-send-email-kan.liang@xxxxxxxxxxxxxxx
---
arch/x86/include/asm/fpu/xstate.h | 3 +-
arch/x86/kernel/fpu/xstate.c | 72 ++++++++++++++++++++++++++++++-
2 files changed, 75 insertions(+)
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 040c4d4..c029fce 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -106,6 +106,9 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i
int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf);
int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf);
void copy_supervisor_to_kernel(struct xregs_state *xsave);
+void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask);
+void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask);
+
/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
int validate_user_xstate_header(const struct xstate_header *hdr);
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index dcf0624..b0c22b7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1361,6 +1361,78 @@ void copy_supervisor_to_kernel(struct xregs_state *xstate)
}
}
+/**
+ * copy_dynamic_supervisor_to_kernel() - Save dynamic supervisor states to
+ * an xsave area
+ * @xstate: A pointer to an xsave area
+ * @mask: Represent the dynamic supervisor features saved into the xsave area
+ *
+ * Only the dynamic supervisor states sets in the mask are saved into the xsave
+ * area (See the comment in XFEATURE_MASK_DYNAMIC for the details of dynamic
+ * supervisor feature). Besides the dynamic supervisor states, the legacy
+ * region and XSAVE header are also saved into the xsave area. The supervisor
+ * features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and
+ * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not saved.
+ *
+ * The xsave area must be 64-bytes aligned.
+ */
+void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask)
+{
+ u64 dynamic_mask = xfeatures_mask_dynamic() & mask;
+ u32 lmask, hmask;
+ int err;
+
+ if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))
+ return;
+
+ if (WARN_ON_FPU(!dynamic_mask))
+ return;
+
+ lmask = dynamic_mask;
+ hmask = dynamic_mask >> 32;
+
+ XSTATE_OP(XSAVES, xstate, lmask, hmask, err);
+
+ /* Should never fault when copying to a kernel buffer */
+ WARN_ON_FPU(err);
+}
+
+/**
+ * copy_kernel_to_dynamic_supervisor() - Restore dynamic supervisor states from
+ * an xsave area
+ * @xstate: A pointer to an xsave area
+ * @mask: Represent the dynamic supervisor features restored from the xsave area
+ *
+ * Only the dynamic supervisor states sets in the mask are restored from the
+ * xsave area (See the comment in XFEATURE_MASK_DYNAMIC for the details of
+ * dynamic supervisor feature). Besides the dynamic supervisor states, the
+ * legacy region and XSAVE header are also restored from the xsave area. The
+ * supervisor features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and
+ * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not restored.
+ *
+ * The xsave area must be 64-bytes aligned.
+ */
+void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask)
+{
+ u64 dynamic_mask = xfeatures_mask_dynamic() & mask;
+ u32 lmask, hmask;
+ int err;
+
+ if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))
+ return;
+
+ if (WARN_ON_FPU(!dynamic_mask))
+ return;
+
+ lmask = dynamic_mask;
+ hmask = dynamic_mask >> 32;
+
+ XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
+
+ /* Should never fault when copying from a kernel buffer */
+ WARN_ON_FPU(err);
+}
+
#ifdef CONFIG_PROC_PID_ARCH_STATUS
/*
* Report the amount of time elapsed in millisecond since last AVX512
|