arch/x86/kernel/xsave.c

   1 /*
   2  * xsave/xrstor support.
   3  *
   4  * Author: Suresh Siddha <suresh.b.siddha@intel.com>
   5  */
   6 #include <linux/bootmem.h>
   7 #include <linux/compat.h>
   8 #include <asm/i387.h>
   9
  10 /*
  11  * Supported feature mask by the CPU and the kernel.
  12  */
  13 unsigned int pcntxt_hmask, pcntxt_lmask;
  14
  15 /*
  16  * Represents init state for the supported extended state.
  17  */
  18 struct xsave_struct *init_xstate_buf;
  19
  20 #ifdef CONFIG_X86_64
  21 unsigned int sig_xstate_size = sizeof(struct _fpstate);
  22 #endif
  23
  24 /*
  25  * Enable the extended processor state save/restore feature
  26  */
  27 void __cpuinit xsave_init(void)
  28 {
  29         if (!cpu_has_xsave)
  30                 return;
  31
  32         set_in_cr4(X86_CR4_OSXSAVE);
  33
  34         /*
  35          * Enable all the features that the HW is capable of
  36          * and the Linux kernel is aware of.
  37          *
  38          * xsetbv();
  39          */
  40         asm volatile(".byte 0x0f,0x01,0xd1" : : "c" (0),
  41                      "a" (pcntxt_lmask), "d" (pcntxt_hmask));
  42 }
  43
  44 /*
  45  * setup the xstate image representing the init state
  46  */
  47 void setup_xstate_init(void)
  48 {
  49         init_xstate_buf = alloc_bootmem(xstate_size);
  50         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
  51 }
  52
  53 /*
  54  * Enable and initialize the xsave feature.
  55  */
  56 void __init xsave_cntxt_init(void)
  57 {
  58         unsigned int eax, ebx, ecx, edx;
  59
  60         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
  61
  62         pcntxt_lmask = eax;
  63         pcntxt_hmask = edx;
  64
  65         if ((pcntxt_lmask & XSTATE_FPSSE) != XSTATE_FPSSE) {
  66                 printk(KERN_ERR "FP/SSE not shown under xsave features %x\n",
  67                        pcntxt_lmask);
  68                 BUG();
  69         }
  70
  71         /*
  72          * for now OS knows only about FP/SSE
  73          */
  74         pcntxt_lmask = pcntxt_lmask & XCNTXT_LMASK;
  75         pcntxt_hmask = pcntxt_hmask & XCNTXT_HMASK;
  76
  77         xsave_init();
  78
  79         /*
  80          * Recompute the context size for enabled features
  81          */
  82         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
  83
  84         xstate_size = ebx;
  85
  86         setup_xstate_init();
  87
  88         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%Lx, "
  89                "cntxt size 0x%x\n",
  90                (pcntxt_lmask | ((u64) pcntxt_hmask << 32)), xstate_size);
  91 }