Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
 "Misc fixes: a SYSRET single-stepping fix, a dmi-scan robustization
  fix, a reboot quirk and a kgdb fixlet"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kgdb/x86: Fix reporting of 'si' in kgdb on x86_64
  x86/asm/entry/64: Disable opportunistic SYSRET if regs->flags has TF set
  x86/reboot: Add ASRock Q1900DC-ITX mainboard reboot quirk
  MAINTAINERS: Change the x86 microcode loader maintainer
  firmware: dmi_scan: Prevent dmi_num integer overflow

Author: torvalds

MAINTAINERS

@@ -637,8 +637,7 @@ F:      drivers/gpu/drm/radeon/radeon_kfd.h
 F:      include/uapi/linux/kfd_ioctl.h
 
 AMD MICROCODE UPDATE SUPPORT
-M:	Andreas Herrmann <[email protected]>
-L:	[email protected]
+M:	Borislav Petkov <[email protected]>
 S:	Maintained
 F:	arch/x86/kernel/cpu/microcode/amd*
 
@@ -5095,7 +5094,7 @@ S:	Supported
 F:	drivers/platform/x86/intel_menlow.c
 
 INTEL IA32 MICROCODE UPDATE SUPPORT
-M:	Tigran Aivazian <[email protected]>
+M:	Borislav Petkov <[email protected]>
 S:	Maintained
 F:	arch/x86/kernel/cpu/microcode/core*
 F:	arch/x86/kernel/cpu/microcode/intel*

arch/x86/kernel/entry_64.S

@@ -799,7 +799,21 @@ retint_swapgs:		/* return to user-space */
 	cmpq %r11,(EFLAGS-ARGOFFSET)(%rsp)	/* R11 == RFLAGS */
 	jne opportunistic_sysret_failed
 
-	testq $X86_EFLAGS_RF,%r11		/* sysret can't restore RF */
+	/*
+	 * SYSRET can't restore RF.  SYSRET can restore TF, but unlike IRET,
+	 * restoring TF results in a trap from userspace immediately after
+	 * SYSRET.  This would cause an infinite loop whenever #DB happens
+	 * with register state that satisfies the opportunistic SYSRET
+	 * conditions.  For example, single-stepping this user code:
+	 *
+	 *           movq $stuck_here,%rcx
+	 *           pushfq
+	 *           popq %r11
+	 *   stuck_here:
+	 *
+	 * would never get past 'stuck_here'.
+	 */
+	testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11
 	jnz opportunistic_sysret_failed
 
 	/* nothing to check for RSP */

arch/x86/kernel/kgdb.c

@@ -72,7 +72,7 @@ struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
 	{ "bx", 8, offsetof(struct pt_regs, bx) },
 	{ "cx", 8, offsetof(struct pt_regs, cx) },
 	{ "dx", 8, offsetof(struct pt_regs, dx) },
-	{ "si", 8, offsetof(struct pt_regs, dx) },
+	{ "si", 8, offsetof(struct pt_regs, si) },
 	{ "di", 8, offsetof(struct pt_regs, di) },
 	{ "bp", 8, offsetof(struct pt_regs, bp) },
 	{ "sp", 8, offsetof(struct pt_regs, sp) },

arch/x86/kernel/reboot.c

@@ -183,6 +183,16 @@ static struct dmi_system_id __initdata reboot_dmi_table[] = {
 		},
 	},
 
+	/* ASRock */
+	{	/* Handle problems with rebooting on ASRock Q1900DC-ITX */
+		.callback = set_pci_reboot,
+		.ident = "ASRock Q1900DC-ITX",
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "ASRock"),
+			DMI_MATCH(DMI_BOARD_NAME, "Q1900DC-ITX"),
+		},
+	},
+
 	/* ASUS */
 	{	/* Handle problems with rebooting on ASUS P4S800 */
 		.callback = set_bios_reboot,

drivers/firmware/dmi_scan.c

@@ -86,10 +86,13 @@ static void dmi_table(u8 *buf, u32 len, int num,
 	int i = 0;
 
 	/*
-	 *	Stop when we see all the items the table claimed to have
-	 *	OR we run off the end of the table (also happens)
+	 * Stop when we have seen all the items the table claimed to have
+	 * (SMBIOS < 3.0 only) OR we reach an end-of-table marker OR we run
+	 * off the end of the table (should never happen but sometimes does
+	 * on bogus implementations.)
 	 */
-	while ((i < num) && (data - buf + sizeof(struct dmi_header)) <= len) {
+	while ((!num || i < num) &&
+	       (data - buf + sizeof(struct dmi_header)) <= len) {
 		const struct dmi_header *dm = (const struct dmi_header *)data;
 
 		/*
@@ -529,21 +532,10 @@ static int __init dmi_smbios3_present(const u8 *buf)
 	if (memcmp(buf, "_SM3_", 5) == 0 &&
 	    buf[6] < 32 && dmi_checksum(buf, buf[6])) {
 		dmi_ver = get_unaligned_be16(buf + 7);
+		dmi_num = 0;			/* No longer specified */
 		dmi_len = get_unaligned_le32(buf + 12);
 		dmi_base = get_unaligned_le64(buf + 16);
 
-		/*
-		 * The 64-bit SMBIOS 3.0 entry point no longer has a field
-		 * containing the number of structures present in the table.
-		 * Instead, it defines the table size as a maximum size, and
-		 * relies on the end-of-table structure type (#127) to be used
-		 * to signal the end of the table.
-		 * So let's define dmi_num as an upper bound as well: each
-		 * structure has a 4 byte header, so dmi_len / 4 is an upper
-		 * bound for the number of structures in the table.
-		 */
-		dmi_num = dmi_len / 4;
-
 		if (dmi_walk_early(dmi_decode) == 0) {
 			pr_info("SMBIOS %d.%d present.\n",
 				dmi_ver >> 8, dmi_ver & 0xFF);