lkml.org 
[lkml]   [2020]   [Jun]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH V2 21/23] x86/fpu/xstate: Add helpers for LBR dynamic supervisor feature
Date
From: Kan Liang <kan.liang@linux.intel.com>

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.

Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
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
--
2.7.4
\
 
 \ /
  Last update: 2020-06-26 20:25    [W:0.153 / U:5.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site