- Allow booting of late secondary CPUs affected by erratum 1418040

(currently they are parked if none of the early CPUs are affected by
   this erratum).
 
 - Add the 32-bit vdso Makefile to the vdso_install rule so that 'make
   vdso_install' installs the 32-bit compat vdso when it is compiled.
 
 - Print a warning that untrusted guests without a CPU erratum workaround
   (Cortex-A57 832075) may deadlock the affected system.
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:

 - Allow booting of late secondary CPUs affected by erratum 1418040
   (currently they are parked if none of the early CPUs are affected by
   this erratum).

 - Add the 32-bit vdso Makefile to the vdso_install rule so that 'make
   vdso_install' installs the 32-bit compat vdso when it is compiled.

 - Print a warning that untrusted guests without a CPU erratum
   workaround (Cortex-A57 832075) may deadlock the affected system.

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  ARM64: vdso32: Install vdso32 from vdso_install
  KVM: arm64: Print warning when cpu erratum can cause guests to deadlock
  arm64: Allow booting of late CPUs affected by erratum 1418040
  arm64: Move handling of erratum 1418040 into C code

arch/arm64/Makefile

@@ -165,6 +165,7 @@ zinstall install:
 PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso $@
+	$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso32 $@
 
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:

arch/arm64/kernel/cpu_errata.c

@@ -910,6 +910,8 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.desc = "ARM erratum 1418040",
 		.capability = ARM64_WORKAROUND_1418040,
 		ERRATA_MIDR_RANGE_LIST(erratum_1418040_list),
+		.type = (ARM64_CPUCAP_SCOPE_LOCAL_CPU |
+			 ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU),
 	},
 #endif
 #ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_AT

arch/arm64/kernel/entry.S

@@ -170,19 +170,6 @@ alternative_cb_end
 	stp	x28, x29, [sp, #16 * 14]
 
 	.if	\el == 0
-	.if	\regsize == 32
-	/*
-	 * If we're returning from a 32-bit task on a system affected by
-	 * 1418040 then re-enable userspace access to the virtual counter.
-	 */
-#ifdef CONFIG_ARM64_ERRATUM_1418040
-alternative_if ARM64_WORKAROUND_1418040
-	mrs	x0, cntkctl_el1
-	orr	x0, x0, #2	// ARCH_TIMER_USR_VCT_ACCESS_EN
-	msr	cntkctl_el1, x0
-alternative_else_nop_endif
-#endif
-	.endif
 	clear_gp_regs
 	mrs	x21, sp_el0
 	ldr_this_cpu	tsk, __entry_task, x20
@@ -294,14 +281,6 @@ alternative_else_nop_endif
 	tst	x22, #PSR_MODE32_BIT		// native task?
 	b.eq	3f
 
-#ifdef CONFIG_ARM64_ERRATUM_1418040
-alternative_if ARM64_WORKAROUND_1418040
-	mrs	x0, cntkctl_el1
-	bic	x0, x0, #2			// ARCH_TIMER_USR_VCT_ACCESS_EN
-	msr	cntkctl_el1, x0
-alternative_else_nop_endif
-#endif
-
 #ifdef CONFIG_ARM64_ERRATUM_845719
 alternative_if ARM64_WORKAROUND_845719
 #ifdef CONFIG_PID_IN_CONTEXTIDR

arch/arm64/kernel/process.c

@@ -515,6 +515,39 @@ static void entry_task_switch(struct task_struct *next)
 	__this_cpu_write(__entry_task, next);
 }
 
+/*
+ * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.
+ * Assuming the virtual counter is enabled at the beginning of times:
+ *
+ * - disable access when switching from a 64bit task to a 32bit task
+ * - enable access when switching from a 32bit task to a 64bit task
+ */
+static void erratum_1418040_thread_switch(struct task_struct *prev,
+					  struct task_struct *next)
+{
+	bool prev32, next32;
+	u64 val;
+
+	if (!(IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) &&
+	      cpus_have_const_cap(ARM64_WORKAROUND_1418040)))
+		return;
+
+	prev32 = is_compat_thread(task_thread_info(prev));
+	next32 = is_compat_thread(task_thread_info(next));
+
+	if (prev32 == next32)
+		return;
+
+	val = read_sysreg(cntkctl_el1);
+
+	if (!next32)
+		val |= ARCH_TIMER_USR_VCT_ACCESS_EN;
+	else
+		val &= ~ARCH_TIMER_USR_VCT_ACCESS_EN;
+
+	write_sysreg(val, cntkctl_el1);
+}
+
 /*
  * Thread switching.
  */
@@ -530,6 +563,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 	entry_task_switch(next);
 	uao_thread_switch(next);
 	ssbs_thread_switch(next);
+	erratum_1418040_thread_switch(prev, next);
 
 	/*
 	 * Complete any pending TLB or cache maintenance on this CPU in case

arch/arm64/kernel/vdso32/Makefile

@@ -208,7 +208,7 @@ quiet_cmd_vdsosym = VDSOSYM $@
       cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
 
 # Install commands for the unstripped file
-quiet_cmd_vdso_install = INSTALL $@
+quiet_cmd_vdso_install = INSTALL32 $@
       cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/vdso32.so
 
 vdso.so: $(obj)/vdso.so.dbg

arch/arm64/kvm/arm.c

@@ -1640,6 +1640,10 @@ int kvm_arch_init(void *opaque)
 		return -ENODEV;
 	}
 
+	if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE))
+		kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
+			 "Only trusted guests should be used on this system.\n");
+
 	for_each_online_cpu(cpu) {
 		smp_call_function_single(cpu, check_kvm_target_cpu, &ret, 1);
 		if (ret < 0) {