tsc: Use alternative delay sources whenever appropriate.

PIT isn't available on some of new hardware including Hyper-V. So
use pmtimer for calibration. Moreover pmtimer calibration is faster, so
use it on coreboor where booting time is important.

Based on patch by Michael Chang.

grub-core/Makefile.am

@@ -101,6 +101,7 @@ if COND_i386_efi
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h
 endif
 
@@ -112,10 +113,12 @@ KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/video_fb.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/gfxterm.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/font.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/bufio.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_i386_multiboot
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_i386_qemu
@@ -154,11 +157,13 @@ KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_ia64_efi
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_mips
@@ -233,11 +238,13 @@ KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/arm/efi/loader.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/arm/system.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_arm64_efi
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h
 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/acpi.h
 endif
 
 if COND_emu

grub-core/Makefile.core.def

@@ -171,8 +171,20 @@ kernel = {
   efi = kern/efi/init.c;
   efi = kern/efi/mm.c;
   efi = term/efi/console.c;
+  efi = kern/acpi.c;
+  efi = kern/efi/acpi.c;
+  i386_coreboot = kern/i386/pc/acpi.c;
+  i386_multiboot = kern/i386/pc/acpi.c;
+  i386_coreboot = kern/acpi.c;
+  i386_multiboot = kern/acpi.c;
 
   x86 = kern/i386/tsc.c;
+  x86 = kern/i386/tsc_pit.c;
+  i386_efi = kern/i386/efi/tsc.c;
+  x86_64_efi = kern/i386/efi/tsc.c;
+  i386_efi = kern/i386/tsc_pmtimer.c;
+  i386_coreboot = kern/i386/tsc_pmtimer.c;
+  x86_64_efi = kern/i386/tsc_pmtimer.c;
 
   i386_efi = kern/i386/efi/init.c;
   i386_efi = bus/pci.c;
@@ -184,6 +196,7 @@ kernel = {
   x86_64_efi = bus/pci.c;
 
   xen = kern/i386/tsc.c;
+  xen = kern/i386/xen/tsc.c;
   x86_64_xen = kern/x86_64/xen/hypercall.S;
   i386_xen = kern/i386/xen/hypercall.S;
   xen = kern/xen/init.c;
@@ -665,10 +678,8 @@ module = {
   name = acpi;
 
   common = commands/acpi.c;
-  efi = commands/efi/acpi.c;
+  i386_pc = kern/acpi.c;
-  i386_pc = commands/i386/pc/acpi.c;
+  i386_pc = kern/i386/pc/acpi.c;
-  i386_coreboot = commands/i386/pc/acpi.c;
-  i386_multiboot = commands/i386/pc/acpi.c;
 
   enable = efi;
   enable = i386_pc;

grub-core/commands/acpi.c

@@ -61,18 +61,6 @@ static const struct grub_arg_option options[] = {
   {0, 0, 0, 0, 0, 0}
 };
 
-/* Simple checksum by summing all bytes. Used by ACPI and SMBIOS. */
-grub_uint8_t
-grub_byte_checksum (void *base, grub_size_t size)
-{
-  grub_uint8_t *ptr;
-  grub_uint8_t ret = 0;
-  for (ptr = (grub_uint8_t *) base; ptr < ((grub_uint8_t *) base) + size;
-       ptr++)
-    ret += *ptr;
-  return ret;
-}
-
 /* rev1 is 1 if ACPIv1 is to be generated, 0 otherwise.
    rev2 contains the revision of ACPIv2+ to generate or 0 if none. */
 static int rev1, rev2;

grub-core/kern/acpi.c

@@ -0,0 +1,34 @@
+/* 
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2012  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/acpi.h>
+
+/* Simple checksum by summing all bytes. Used by ACPI and SMBIOS. */
+grub_uint8_t
+grub_byte_checksum (void *base, grub_size_t size)
+{
+  grub_uint8_t *ptr;
+  grub_uint8_t ret = 0;
+  for (ptr = (grub_uint8_t *) base; ptr < ((grub_uint8_t *) base) + size;
+       ptr++)
+    ret += *ptr;
+  return ret;
+}

grub-core/kern/i386/efi/tsc.c

@@ -0,0 +1,40 @@
+/* kern/i386/tsc.c - x86 TSC time source implementation
+ * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
+ * This module uses the PIT to calibrate the TSC to
+ * real time.
+ *
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/i386/tsc.h>
+#include <grub/efi/efi.h>
+#include <grub/efi/api.h>
+
+int
+grub_tsc_calibrate_from_efi (void)
+{
+  grub_uint64_t start_tsc, end_tsc;
+  /* Use EFI Time Service to calibrate TSC */
+  start_tsc = grub_get_tsc ();
+  efi_call_1 (grub_efi_system_table->boot_services->stall, 1000);
+  end_tsc = grub_get_tsc ();
+  grub_tsc_rate = grub_divmod64 ((1ULL << 32), end_tsc - start_tsc, 0);
+  return 1;
+}

grub-core/kern/i386/tsc.c

@@ -1,7 +1,6 @@
 /* kern/i386/tsc.c - x86 TSC time source implementation
  * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
- * This module uses the RTC (via grub_get_rtc()) to calibrate the TSC to
+ * This module calibrates the TSC to real time.
- * real time.
  *
  *  GRUB  --  GRand Unified Bootloader
  *  Copyright (C) 2008  Free Software Foundation, Inc.
@@ -25,12 +24,6 @@
 #include <grub/misc.h>
 #include <grub/i386/tsc.h>
 #include <grub/i386/cpuid.h>
-#ifdef GRUB_MACHINE_XEN
-#include <grub/xen.h>
-#else
-#include <grub/i386/pit.h>
-#endif
-#include <grub/cpu/io.h>
 
 /* This defines the value TSC had at the epoch (that is, when we calibrated it). */
 static grub_uint64_t tsc_boot_time;
@@ -40,66 +33,6 @@ static grub_uint64_t tsc_boot_time;
    in 32-bit.  */
 grub_uint32_t grub_tsc_rate;
 
-/* Read the TSC value, which increments with each CPU clock cycle. */
-static __inline grub_uint64_t
-grub_get_tsc (void)
-{
-  grub_uint32_t lo, hi;
-  grub_uint32_t a,b,c,d;
-
-  /* The CPUID instruction is a 'serializing' instruction, and
-     avoids out-of-order execution of the RDTSC instruction. */
-  grub_cpuid (0,a,b,c,d);
-  /* Read TSC value.  We cannot use "=A", since this would use
-     %rax on x86_64. */
-  __asm__ __volatile__ ("rdtsc":"=a" (lo), "=d" (hi));
-
-  return (((grub_uint64_t) hi) << 32) | lo;
-}
-
-#ifndef GRUB_MACHINE_XEN
-
-static __inline int
-grub_cpu_is_tsc_supported (void)
-{
-  grub_uint32_t a,b,c,d;
-  if (! grub_cpu_is_cpuid_supported ())
-    return 0;
-
-  grub_cpuid(1,a,b,c,d);
-
-  return (d & (1 << 4)) != 0;
-}
-
-static void
-grub_pit_wait (grub_uint16_t tics)
-{
-  /* Disable timer2 gate and speaker.  */
-  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
-	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
-             GRUB_PIT_SPEAKER_PORT);
-
-  /* Set tics.  */
-  grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD,
-	     GRUB_PIT_CTRL);
-  grub_outb (tics & 0xff, GRUB_PIT_COUNTER_2);
-  grub_outb (tics >> 8, GRUB_PIT_COUNTER_2);
-
-  /* Enable timer2 gate, keep speaker disabled.  */
-  grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA)
-	     | GRUB_PIT_SPK_TMR2,
-             GRUB_PIT_SPEAKER_PORT);
-
-  /* Wait.  */
-  while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00);
-
-  /* Disable timer2 gate and speaker.  */
-  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
-	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
-             GRUB_PIT_SPEAKER_PORT);
-}
-#endif
-
 static grub_uint64_t
 grub_tsc_get_time_ms (void)
 {
@@ -110,52 +43,52 @@ grub_tsc_get_time_ms (void)
   return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
 }
 
-#ifndef GRUB_MACHINE_XEN
+static __inline int
-/* Calibrate the TSC based on the RTC.  */
+grub_cpu_is_tsc_supported (void)
-static void
-calibrate_tsc (void)
 {
-  /* First calibrate the TSC rate (relative, not absolute time). */
+#ifndef GRUB_MACHINE_XEN
-  grub_uint64_t end_tsc;
+  grub_uint32_t a,b,c,d;
+  if (! grub_cpu_is_cpuid_supported ())
+    return 0;
 
-  tsc_boot_time = grub_get_tsc ();
+  grub_cpuid(1,a,b,c,d);
-  grub_pit_wait (0xffff);
-  end_tsc = grub_get_tsc ();
 
-  grub_tsc_rate = 0;
+  return (d & (1 << 4)) != 0;
-  if (end_tsc > tsc_boot_time)
+#else
-    grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - tsc_boot_time, 0);
+  return 1;
-  if (grub_tsc_rate == 0)
-    grub_tsc_rate = 5368;/* 800 MHz */
-}
 #endif
+}
+
+static int
+calibrate_tsc_hardcode (void)
+{
+  grub_tsc_rate = 5368;/* 800 MHz */
+  return 1;
+}
 
 void
 grub_tsc_init (void)
 {
-#ifdef GRUB_MACHINE_XEN
+  if (!grub_cpu_is_tsc_supported ())
-  grub_uint64_t t;
-  tsc_boot_time = grub_get_tsc ();
-  t = grub_xen_shared_info->vcpu_info[0].time.tsc_to_system_mul;
-  if (grub_xen_shared_info->vcpu_info[0].time.tsc_shift > 0)
-    t <<= grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
-  else
-    t >>= -grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
-  grub_tsc_rate = grub_divmod64 (t, 1000000, 0);
-  grub_install_get_time_ms (grub_tsc_get_time_ms);
-#else
-  if (grub_cpu_is_tsc_supported ())
-    {
-      calibrate_tsc ();
-      grub_install_get_time_ms (grub_tsc_get_time_ms);
-    }
-  else
     {
 #if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275)
       grub_install_get_time_ms (grub_rtc_get_time_ms);
 #else
       grub_fatal ("no TSC found");
 #endif
+      return;
     }
+
+  tsc_boot_time = grub_get_tsc ();
+
+#ifdef GRUB_MACHINE_XEN
+  (void) (grub_tsc_calibrate_from_xen () || calibrate_tsc_hardcode());
+#elif defined (GRUB_MACHINE_EFI)
+  (void) (grub_tsc_calibrate_from_pit () || grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_efi() || calibrate_tsc_hardcode());
+#elif defined (GRUB_MACHINE_COREBOOT)
+  (void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
+#else
+  (void) (grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode());
 #endif
+  grub_install_get_time_ms (grub_tsc_get_time_ms);
 }

grub-core/kern/i386/tsc_pit.c

@@ -0,0 +1,84 @@
+/* kern/i386/tsc.c - x86 TSC time source implementation
+ * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
+ * This module uses the PIT to calibrate the TSC to
+ * real time.
+ *
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/i386/tsc.h>
+#include <grub/i386/pit.h>
+#include <grub/cpu/io.h>
+
+static int
+grub_pit_wait (void)
+{
+  int ret = 0;
+
+  /* Disable timer2 gate and speaker.  */
+  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
+	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
+             GRUB_PIT_SPEAKER_PORT);
+
+  /* Set tics.  */
+  grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD,
+	     GRUB_PIT_CTRL);
+  /* 0xffff ticks: 55ms. */
+  grub_outb (0xff, GRUB_PIT_COUNTER_2);
+  grub_outb (0xff, GRUB_PIT_COUNTER_2);
+
+  /* Enable timer2 gate, keep speaker disabled.  */
+  grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA)
+	     | GRUB_PIT_SPK_TMR2,
+             GRUB_PIT_SPEAKER_PORT);
+
+  if ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH)) {
+    ret = 1;
+    /* Wait.  */
+    while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00);
+  }
+
+  /* Disable timer2 gate and speaker.  */
+  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
+	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
+             GRUB_PIT_SPEAKER_PORT);
+
+  return ret;
+}
+
+/* Calibrate the TSC based on the RTC.  */
+int
+grub_tsc_calibrate_from_pit (void)
+{
+  /* First calibrate the TSC rate (relative, not absolute time). */
+  grub_uint64_t start_tsc, end_tsc;
+
+  start_tsc = grub_get_tsc ();
+  if (!grub_pit_wait ())
+    return 0;
+  end_tsc = grub_get_tsc ();
+
+  grub_tsc_rate = 0;
+  if (end_tsc > start_tsc)
+    grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - start_tsc, 0);
+  if (grub_tsc_rate == 0)
+    return 0;
+  return 1;
+}

grub-core/kern/i386/tsc_pmtimer.c

@@ -0,0 +1,160 @@
+/* kern/i386/tsc.c - x86 TSC time source implementation
+ * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
+ * This module uses the PIT to calibrate the TSC to
+ * real time.
+ *
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/i386/tsc.h>
+#include <grub/acpi.h>
+#include <grub/cpu/io.h>
+
+static void *
+grub_acpi_rsdt_find_table (struct grub_acpi_table_header *rsdt, const char *sig)
+{
+  grub_size_t s;
+  grub_uint32_t *ptr;
+
+  if (!rsdt)
+    return 0;
+
+  if (grub_memcmp (rsdt->signature, "RSDT", 4) != 0)
+    return 0;
+
+  ptr = (grub_uint32_t *) (rsdt + 1);
+  s = (rsdt->length - sizeof (*rsdt)) / sizeof (grub_uint32_t);
+  for (; s; s--, ptr++)
+    {
+      struct grub_acpi_table_header *tbl;
+      tbl = (struct grub_acpi_table_header *) (grub_addr_t) *ptr;
+      if (grub_memcmp (tbl->signature, sig, 4) == 0)
+	return tbl;
+    }
+  return 0;
+}
+
+static void *
+grub_acpi_xsdt_find_table (struct grub_acpi_table_header *xsdt, const char *sig)
+{
+  grub_size_t s;
+  grub_uint64_t *ptr;
+
+  if (!xsdt)
+    return 0;
+
+  if (grub_memcmp (xsdt->signature, "XSDT", 4) != 0)
+    return 0;
+
+  ptr = (grub_uint64_t *) (xsdt + 1);
+  s = (xsdt->length - sizeof (*xsdt)) / sizeof (grub_uint32_t);
+  for (; s; s--, ptr++)
+    {
+      struct grub_acpi_table_header *tbl;
+#if GRUB_CPU_SIZEOF_VOID_P != 8
+      if (*ptr >> 32)
+	continue;
+#endif
+      tbl = (struct grub_acpi_table_header *) (grub_addr_t) *ptr;
+      if (grub_memcmp (tbl->signature, sig, 4) == 0)
+	return tbl;
+    }
+  return 0;
+}
+
+struct grub_acpi_fadt *
+grub_acpi_find_fadt (void)
+{
+  struct grub_acpi_fadt *fadt = 0;
+  struct grub_acpi_rsdp_v10 *rsdpv1;
+  struct grub_acpi_rsdp_v20 *rsdpv2;
+  rsdpv1 = grub_machine_acpi_get_rsdpv1 ();
+  if (rsdpv1)
+    fadt = grub_acpi_rsdt_find_table ((struct grub_acpi_table_header *)
+				      (grub_addr_t) rsdpv1->rsdt_addr,
+				      GRUB_ACPI_FADT_SIGNATURE);
+  if (fadt)
+    return fadt;
+  rsdpv2 = grub_machine_acpi_get_rsdpv2 ();
+  if (rsdpv2)
+    fadt = grub_acpi_rsdt_find_table ((struct grub_acpi_table_header *)
+				      (grub_addr_t) rsdpv2->rsdpv1.rsdt_addr,
+				      GRUB_ACPI_FADT_SIGNATURE);
+  if (fadt)
+    return fadt;
+  if (rsdpv2
+#if GRUB_CPU_SIZEOF_VOID_P != 8
+      && !(rsdpv2->xsdt_addr >> 32)
+#endif
+      )
+    fadt = grub_acpi_xsdt_find_table ((struct grub_acpi_table_header *)
+				      (grub_addr_t) rsdpv2->xsdt_addr,
+				      GRUB_ACPI_FADT_SIGNATURE);
+  if (fadt)
+    return fadt;
+  return 0;
+}
+
+int
+grub_tsc_calibrate_from_pmtimer (void)
+{
+  grub_uint32_t start;
+  grub_uint32_t last;
+  grub_uint32_t cur, end;
+  struct grub_acpi_fadt *fadt;
+  grub_port_t p;
+  grub_uint64_t start_tsc;
+  grub_uint64_t end_tsc;
+  int num_iter = 0;
+
+  fadt = grub_acpi_find_fadt ();
+  if (!fadt)
+    return 0;
+  p = fadt->pmtimer;
+  if (!p)
+    return 0;
+
+  start = grub_inl (p) & 0xffffff;
+  last = start;
+  /* It's 3.579545 MHz clock. Wait 1 ms.  */
+  end = start + 3580;
+  start_tsc = grub_get_tsc ();
+  while (1)
+    {
+      cur = grub_inl (p) & 0xffffff;
+      if (cur < last)
+	cur |= 0x1000000;
+      num_iter++;
+      if (cur >= end)
+	{
+	  end_tsc = grub_get_tsc ();
+	  grub_tsc_rate = grub_divmod64 ((1ULL << 32), end_tsc - start_tsc, 0);
+	  return 1;
+	}
+      /* Check for broken PM timer.
+	 50000000 TSCs is between 5 ms (10GHz) and 200 ms (250 MHz)
+	 if after this time we still don't have 1 ms on pmtimer, then
+	 pmtimer is broken.
+       */
+      if ((num_iter & 0xffffff) == 0 && grub_get_tsc () - start_tsc > 5000000) {
+	return 0;
+      }
+    }
+}

grub-core/kern/i386/xen/tsc.c

@@ -0,0 +1,40 @@
+/* kern/i386/tsc.c - x86 TSC time source implementation
+ * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
+ * This module uses the PIT to calibrate the TSC to
+ * real time.
+ *
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/types.h>
+#include <grub/time.h>
+#include <grub/misc.h>
+#include <grub/i386/tsc.h>
+#include <grub/xen.h>
+
+int
+grub_tsc_calibrate_from_xen (void)
+{
+  grub_uint64_t t;
+  t = grub_xen_shared_info->vcpu_info[0].time.tsc_to_system_mul;
+  if (grub_xen_shared_info->vcpu_info[0].time.tsc_shift > 0)
+    t <<= grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
+  else
+    t >>= -grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
+  grub_tsc_rate = grub_divmod64 (t, 1000000, 0);
+  return 1;
+}

include/grub/acpi.h

@@ -67,10 +67,14 @@ struct grub_acpi_fadt
   grub_uint32_t dsdt_addr;
   grub_uint8_t somefields1[20];
   grub_uint32_t pm1a;
-  grub_uint8_t somefields2[64];
+  grub_uint8_t somefields2[8];
+  grub_uint32_t pmtimer;
+  grub_uint8_t somefields3[32];
+  grub_uint32_t flags;
+  grub_uint8_t somefields4[16];
   grub_uint64_t facs_xaddr;
   grub_uint64_t dsdt_xaddr;
-  grub_uint8_t somefields3[96];
+  grub_uint8_t somefields5[96];
 } GRUB_PACKED;
 
 #define GRUB_ACPI_MADT_SIGNATURE "APIC"
@@ -176,9 +180,9 @@ enum
 #ifndef GRUB_DSDT_TEST
 struct grub_acpi_rsdp_v10 *grub_acpi_get_rsdpv1 (void);
 struct grub_acpi_rsdp_v20 *grub_acpi_get_rsdpv2 (void);
-struct grub_acpi_rsdp_v10 *grub_machine_acpi_get_rsdpv1 (void);
+struct grub_acpi_rsdp_v10 *EXPORT_FUNC(grub_machine_acpi_get_rsdpv1) (void);
-struct grub_acpi_rsdp_v20 *grub_machine_acpi_get_rsdpv2 (void);
+struct grub_acpi_rsdp_v20 *EXPORT_FUNC(grub_machine_acpi_get_rsdpv2) (void);
-grub_uint8_t grub_byte_checksum (void *base, grub_size_t size);
+grub_uint8_t EXPORT_FUNC(grub_byte_checksum) (void *base, grub_size_t size);
 
 grub_err_t grub_acpi_create_ebda (void);
 
@@ -234,4 +238,7 @@ enum
     GRUB_ACPI_EXTOPCODE_BANK_FIELD_OP = 0x87,
   };
 
+struct grub_acpi_fadt *
+grub_acpi_find_fadt (void);
+
 #endif /* ! GRUB_ACPI_HEADER */

include/grub/i386/tsc.h

@@ -20,9 +20,35 @@
 #define KERNEL_CPU_TSC_HEADER   1
 
 #include <grub/types.h>
+#include <grub/i386/cpuid.h>
 
 void grub_tsc_init (void);
 /* In ms per 2^32 ticks.  */
 extern grub_uint32_t EXPORT_VAR(grub_tsc_rate);
+int
+grub_tsc_calibrate_from_xen (void);
+int
+grub_tsc_calibrate_from_efi (void);
+int
+grub_tsc_calibrate_from_pmtimer (void);
+int
+grub_tsc_calibrate_from_pit (void);
+
+/* Read the TSC value, which increments with each CPU clock cycle. */
+static __inline grub_uint64_t
+grub_get_tsc (void)
+{
+  grub_uint32_t lo, hi;
+  grub_uint32_t a,b,c,d;
+
+  /* The CPUID instruction is a 'serializing' instruction, and
+     avoids out-of-order execution of the RDTSC instruction. */
+  grub_cpuid (0,a,b,c,d);
+  /* Read TSC value.  We cannot use "=A", since this would use
+     %rax on x86_64. */
+  __asm__ __volatile__ ("rdtsc":"=a" (lo), "=d" (hi));
+
+  return (((grub_uint64_t) hi) << 32) | lo;
+}
 
 #endif /* ! KERNEL_CPU_TSC_HEADER */