Merge tag 'x86-urgent-2022-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc x86 fixes from Ingo Molnar:

 - Fix PAT on Xen, which caused i915 driver failures

 - Fix compat INT 80 entry crash on Xen PV guests

 - Fix 'MMIO Stale Data' mitigation status reporting on older Intel CPUs

 - Fix RSB stuffing regressions

 - Fix ORC unwinding on ftrace trampolines

 - Add Intel Raptor Lake CPU model number

 - Fix (work around) a SEV-SNP bootloader bug providing bogus values in
   boot_params->cc_blob_address, by ignoring the value on !SEV-SNP
   bootups.

 - Fix SEV-SNP early boot failure

 - Fix the objtool list of noreturn functions and annotate snp_abort(),
   which bug confused objtool on gcc-12.

 - Fix the documentation for retbleed

* tag 'x86-urgent-2022-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation/ABI: Mention retbleed vulnerability info file for sysfs
  x86/sev: Mark snp_abort() noreturn
  x86/sev: Don't use cc_platform_has() for early SEV-SNP calls
  x86/boot: Don't propagate uninitialized boot_params->cc_blob_address
  x86/cpu: Add new Raptor Lake CPU model number
  x86/unwind/orc: Unwind ftrace trampolines with correct ORC entry
  x86/nospec: Fix i386 RSB stuffing
  x86/nospec: Unwreck the RSB stuffing
  x86/bugs: Add "unknown" reporting for MMIO Stale Data
  x86/entry: Fix entry_INT80_compat for Xen PV guests
  x86/PAT: Have pat_enabled() properly reflect state when running on Xen

4 files changed, 57 insertions, 44 deletions

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 235dc85c91c3..ef4775c6db01 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -457,7 +457,8 @@
 #define X86_BUG_ITLB_MULTIHIT		X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
 #define X86_BUG_SRBDS			X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
 #define X86_BUG_MMIO_STALE_DATA		X86_BUG(25) /* CPU is affected by Processor MMIO Stale Data vulnerabilities */
-#define X86_BUG_RETBLEED		X86_BUG(26) /* CPU is affected by RETBleed */
-#define X86_BUG_EIBRS_PBRSB		X86_BUG(27) /* EIBRS is vulnerable to Post Barrier RSB Predictions */
+#define X86_BUG_MMIO_UNKNOWN		X86_BUG(26) /* CPU is too old and its MMIO Stale Data status is unknown */
+#define X86_BUG_RETBLEED		X86_BUG(27) /* CPU is affected by RETBleed */
+#define X86_BUG_EIBRS_PBRSB		X86_BUG(28) /* EIBRS is vulnerable to Post Barrier RSB Predictions */
 
 #endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/intel-family.h b/arch/x86/include/asm/intel-family.h
index def6ca121111..aeb38023a703 100644
--- a/arch/x86/include/asm/intel-family.h
+++ b/arch/x86/include/asm/intel-family.h
@@ -27,6 +27,7 @@
  *		_X	- regular server parts
  *		_D	- micro server parts
  *		_N,_P	- other mobile parts
+ *		_S	- other client parts
  *
  *		Historical OPTDIFFs:
  *
@@ -112,6 +113,7 @@
 
 #define INTEL_FAM6_RAPTORLAKE		0xB7
 #define INTEL_FAM6_RAPTORLAKE_P		0xBA
+#define INTEL_FAM6_RAPTORLAKE_S		0xBF
 
 /* "Small Core" Processors (Atom) */
 
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index e64fd20778b6..c936ce9f0c47 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -35,33 +35,56 @@
 #define RSB_CLEAR_LOOPS		32	/* To forcibly overwrite all entries */
 
 /*
+ * Common helper for __FILL_RETURN_BUFFER and __FILL_ONE_RETURN.
+ */
+#define __FILL_RETURN_SLOT			\
+	ANNOTATE_INTRA_FUNCTION_CALL;		\
+	call	772f;				\
+	int3;					\
+772:
+
+/*
+ * Stuff the entire RSB.
+ *
  * Google experimented with loop-unrolling and this turned out to be
  * the optimal version - two calls, each with their own speculation
  * trap should their return address end up getting used, in a loop.
  */
-#define __FILL_RETURN_BUFFER(reg, nr, sp)	\
-	mov	$(nr/2), reg;			\
-771:						\
-	ANNOTATE_INTRA_FUNCTION_CALL;		\
-	call	772f;				\
-773:	/* speculation trap */			\
-	UNWIND_HINT_EMPTY;			\
-	pause;					\
-	lfence;					\
-	jmp	773b;				\
-772:						\
-	ANNOTATE_INTRA_FUNCTION_CALL;		\
-	call	774f;				\
-775:	/* speculation trap */			\
-	UNWIND_HINT_EMPTY;			\
-	pause;					\
-	lfence;					\
-	jmp	775b;				\
-774:						\
-	add	$(BITS_PER_LONG/8) * 2, sp;	\
-	dec	reg;				\
-	jnz	771b;				\
-	/* barrier for jnz misprediction */	\
+#ifdef CONFIG_X86_64
+#define __FILL_RETURN_BUFFER(reg, nr)			\
+	mov	$(nr/2), reg;				\
+771:							\
+	__FILL_RETURN_SLOT				\
+	__FILL_RETURN_SLOT				\
+	add	$(BITS_PER_LONG/8) * 2, %_ASM_SP;	\
+	dec	reg;					\
+	jnz	771b;					\
+	/* barrier for jnz misprediction */		\
+	lfence;
+#else
+/*
+ * i386 doesn't unconditionally have LFENCE, as such it can't
+ * do a loop.
+ */
+#define __FILL_RETURN_BUFFER(reg, nr)			\
+	.rept nr;					\
+	__FILL_RETURN_SLOT;				\
+	.endr;						\
+	add	$(BITS_PER_LONG/8) * nr, %_ASM_SP;
+#endif
+
+/*
+ * Stuff a single RSB slot.
+ *
+ * To mitigate Post-Barrier RSB speculation, one CALL instruction must be
+ * forced to retire before letting a RET instruction execute.
+ *
+ * On PBRSB-vulnerable CPUs, it is not safe for a RET to be executed
+ * before this point.
+ */
+#define __FILL_ONE_RETURN				\
+	__FILL_RETURN_SLOT				\
+	add	$(BITS_PER_LONG/8), %_ASM_SP;		\
 	lfence;
 
 #ifdef __ASSEMBLY__
@@ -132,28 +155,15 @@
 #endif
 .endm
 
-.macro ISSUE_UNBALANCED_RET_GUARD
-	ANNOTATE_INTRA_FUNCTION_CALL
-	call .Lunbalanced_ret_guard_\@
-	int3
-.Lunbalanced_ret_guard_\@:
-	add $(BITS_PER_LONG/8), %_ASM_SP
-	lfence
-.endm
-
  /*
   * A simpler FILL_RETURN_BUFFER macro. Don't make people use the CPP
   * monstrosity above, manually.
   */
-.macro FILL_RETURN_BUFFER reg:req nr:req ftr:req ftr2
-.ifb \ftr2
-	ALTERNATIVE "jmp .Lskip_rsb_\@", "", \ftr
-.else
-	ALTERNATIVE_2 "jmp .Lskip_rsb_\@", "", \ftr, "jmp .Lunbalanced_\@", \ftr2
-.endif
-	__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)
-.Lunbalanced_\@:
-	ISSUE_UNBALANCED_RET_GUARD
+.macro FILL_RETURN_BUFFER reg:req nr:req ftr:req ftr2=ALT_NOT(X86_FEATURE_ALWAYS)
+	ALTERNATIVE_2 "jmp .Lskip_rsb_\@", \
+		__stringify(__FILL_RETURN_BUFFER(\reg,\nr)), \ftr, \
+		__stringify(__FILL_ONE_RETURN), \ftr2
+
 .Lskip_rsb_\@:
 .endm
 
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 4a23e52fe0ee..ebc271bb6d8e 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -195,7 +195,7 @@ void snp_set_memory_shared(unsigned long vaddr, unsigned int npages);
 void snp_set_memory_private(unsigned long vaddr, unsigned int npages);
 void snp_set_wakeup_secondary_cpu(void);
 bool snp_init(struct boot_params *bp);
-void snp_abort(void);
+void __init __noreturn snp_abort(void);
 int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }