Merge tag 'x86-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Thomas Gleixner:
 "A series of fixes for x86:

   - Reset MXCSR in kernel_fpu_begin() to prevent using a stale user
     space value.

   - Prevent writing MSR_TEST_CTRL on CPUs which are not explicitly
     whitelisted for split lock detection. Some CPUs which do not
     support it crash even when the MSR is written to 0 which is the
     default value.

   - Fix the XEN PV fallout of the entry code rework

   - Fix the 32bit fallout of the entry code rework

   - Add more selftests to ensure that these entry problems don't come
     back.

   - Disable 16 bit segments on XEN PV. It's not supported because XEN
     PV does not implement ESPFIX64"

* tag 'x86-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/ldt: Disable 16-bit segments on Xen PV
  x86/entry/32: Fix #MC and #DB wiring on x86_32
  x86/entry/xen: Route #DB correctly on Xen PV
  x86/entry, selftests: Further improve user entry sanity checks
  x86/entry/compat: Clear RAX high bits on Xen PV SYSENTER
  selftests/x86: Consolidate and fix get/set_eflags() helpers
  selftests/x86/syscall_nt: Clear weird flags after each test
  selftests/x86/syscall_nt: Add more flag combinations
  x86/entry/64/compat: Fix Xen PV SYSENTER frame setup
  x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C
  x86/entry: Assert that syscalls are on the right stack
  x86/split_lock: Don't write MSR_TEST_CTRL on CPUs that aren't whitelisted
  x86/fpu: Reset MXCSR to default in kernel_fpu_begin()

2 files changed, 24 insertions, 28 deletions

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 42159f45bf9c..845e7481ab77 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -623,6 +623,11 @@ static inline void switch_fpu_finish(struct fpu *new_fpu)
  * MXCSR and XCR definitions:
  */
 
+static inline void ldmxcsr(u32 mxcsr)
+{
+	asm volatile("ldmxcsr %0" :: "m" (mxcsr));
+}
+
 extern unsigned int mxcsr_feature_mask;
 
 #define XCR_XFEATURE_ENABLED_MASK	0x00000000
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index cf51c50eb356..eeac6dc2adaa 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -353,10 +353,6 @@ static __always_inline void __##func(struct pt_regs *regs)
 
 #else	/* CONFIG_X86_64 */
 
-/* Maps to a regular IDTENTRY on 32bit for now */
-# define DECLARE_IDTENTRY_IST		DECLARE_IDTENTRY
-# define DEFINE_IDTENTRY_IST		DEFINE_IDTENTRY
-
 /**
  * DECLARE_IDTENTRY_DF - Declare functions for double fault 32bit variant
  * @vector:	Vector number (ignored for C)
@@ -387,28 +383,18 @@ __visible noinstr void func(struct pt_regs *regs,			\
 #endif	/* !CONFIG_X86_64 */
 
 /* C-Code mapping */
+#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_RAW
+#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_RAW
+
+#ifdef CONFIG_X86_64
 #define DECLARE_IDTENTRY_MCE		DECLARE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_MCE		DEFINE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_MCE_USER	DEFINE_IDTENTRY_NOIST
 
-#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_RAW
-#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_RAW
-
 #define DECLARE_IDTENTRY_DEBUG		DECLARE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_DEBUG		DEFINE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_DEBUG_USER	DEFINE_IDTENTRY_NOIST
-
-/**
- * DECLARE_IDTENTRY_XEN - Declare functions for XEN redirect IDT entry points
- * @vector:	Vector number (ignored for C)
- * @func:	Function name of the entry point
- *
- * Used for xennmi and xendebug redirections. No DEFINE as this is all ASM
- * indirection magic.
- */
-#define DECLARE_IDTENTRY_XEN(vector, func)				\
-	asmlinkage void xen_asm_exc_xen##func(void);			\
-	asmlinkage void asm_exc_xen##func(void)
+#endif
 
 #else /* !__ASSEMBLY__ */
 
@@ -455,9 +441,6 @@ __visible noinstr void func(struct pt_regs *regs,			\
 # define DECLARE_IDTENTRY_MCE(vector, func)				\
 	DECLARE_IDTENTRY(vector, func)
 
-# define DECLARE_IDTENTRY_DEBUG(vector, func)				\
-	DECLARE_IDTENTRY(vector, func)
-
 /* No ASM emitted for DF as this goes through a C shim */
 # define DECLARE_IDTENTRY_DF(vector, func)
 
@@ -469,10 +452,6 @@ __visible noinstr void func(struct pt_regs *regs,			\
 /* No ASM code emitted for NMI */
 #define DECLARE_IDTENTRY_NMI(vector, func)
 
-/* XEN NMI and DB wrapper */
-#define DECLARE_IDTENTRY_XEN(vector, func)				\
-	idtentry vector asm_exc_xen##func exc_##func has_error_code=0
-
 /*
  * ASM code to emit the common vector entry stubs where each stub is
  * packed into 8 bytes.
@@ -565,16 +544,28 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_BP,		exc_int3);
 DECLARE_IDTENTRY_RAW_ERRORCODE(X86_TRAP_PF,	exc_page_fault);
 
 #ifdef CONFIG_X86_MCE
+#ifdef CONFIG_X86_64
 DECLARE_IDTENTRY_MCE(X86_TRAP_MC,	exc_machine_check);
+#else
+DECLARE_IDTENTRY_RAW(X86_TRAP_MC,	exc_machine_check);
+#endif
 #endif
 
 /* NMI */
 DECLARE_IDTENTRY_NMI(X86_TRAP_NMI,	exc_nmi);
-DECLARE_IDTENTRY_XEN(X86_TRAP_NMI,	nmi);
+#ifdef CONFIG_XEN_PV
+DECLARE_IDTENTRY_RAW(X86_TRAP_NMI,	xenpv_exc_nmi);
+#endif
 
 /* #DB */
+#ifdef CONFIG_X86_64
 DECLARE_IDTENTRY_DEBUG(X86_TRAP_DB,	exc_debug);
-DECLARE_IDTENTRY_XEN(X86_TRAP_DB,	debug);
+#else
+DECLARE_IDTENTRY_RAW(X86_TRAP_DB,	exc_debug);
+#endif
+#ifdef CONFIG_XEN_PV
+DECLARE_IDTENTRY_RAW(X86_TRAP_DB,	xenpv_exc_debug);
+#endif
 
 /* #DF */
 DECLARE_IDTENTRY_DF(X86_TRAP_DF,	exc_double_fault);