x86/xsaves: Enable xsaves/xrstors

If xsaves/xrstors is enabled, compacted format of xsave area will be used
and less memory may be used for context per process. And modified
optimization implemented in xsaves/xrstors improves performance of saving
xstate.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1401387164-43416-16-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 33 insertions, 6 deletions

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 8fa7c7d4183d..f930f8ab92d1 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -8,6 +8,7 @@
 
 #include <linux/bootmem.h>
 #include <linux/compat.h>
+#include <linux/cpu.h>
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/sigframe.h>
@@ -24,7 +25,9 @@ u64 pcntxt_mask;
 struct xsave_struct *init_xstate_buf;
 
 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
-static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
+static unsigned int *xstate_offsets, *xstate_sizes;
+static unsigned int *xstate_comp_offsets, *xstate_comp_sizes;
+static unsigned int xstate_features;
 
 /*
  * If a processor implementation discern that a processor state component is
@@ -283,7 +286,7 @@ sanitize_restored_xstate(struct task_struct *tsk,
 
         if (use_xsave()) {
                 /* These bits must be zero. */
-                xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
+                memset(xsave_hdr->reserved, 0, 48);
 
                 /*
                  * Init the state that is not present in the memory
@@ -526,6 +529,30 @@ static int __init eager_fpu_setup(char *s)
 }
 __setup("eagerfpu=", eager_fpu_setup);
 
+
+/*
+ * Calculate total size of enabled xstates in XCR0/pcntxt_mask.
+ */
+static void __init init_xstate_size(void)
+{
+        unsigned int eax, ebx, ecx, edx;
+        int i;
+
+        if (!cpu_has_xsaves) {
+                cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
+                xstate_size = ebx;
+                return;
+        }
+
+        xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
+        for (i = 2; i < 64; i++) {
+                if (test_bit(i, (unsigned long *)&pcntxt_mask)) {
+                        cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
+                        xstate_size += eax;
+                }
+        }
+}
+
 /*
  * Enable and initialize the xsave feature.
  */
@@ -557,8 +584,7 @@ static void __init xstate_enable_boot_cpu(void)
         /*
          * Recompute the context size for enabled features
          */
-        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
-        xstate_size = ebx;
+        init_xstate_size();
 
         update_regset_xstate_info(xstate_size, pcntxt_mask);
         prepare_fx_sw_frame();
@@ -578,8 +604,9 @@ static void __init xstate_enable_boot_cpu(void)
                 }
         }
 
-        pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
-                pcntxt_mask, xstate_size);
+        pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x using %s\n",
+                pcntxt_mask, xstate_size,
+                cpu_has_xsaves ? "compacted form" : "standard form");
 }
 
 /*