Merge remote-tracking branch 'arm64/for-next/vhe-only' into kvmarm-master/next

Signed-off-by: Marc Zyngier <maz@kernel.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -2279,8 +2279,7 @@
 				   state is kept private from the host.
 				   Not valid if the kernel is running in EL2.
 
-			Defaults to VHE/nVHE based on hardware support and
+			Defaults to VHE/nVHE based on hardware support.
-			the value of CONFIG_ARM64_VHE.
 
 	kvm-arm.vgic_v3_group0_trap=
 			[KVM,ARM] Trap guest accesses to GICv3 group-0

arch/arm64/Kconfig

@@ -1416,19 +1416,6 @@ config ARM64_USE_LSE_ATOMICS
 	  built with binutils >= 2.25 in order for the new instructions
 	  to be used.
 
-config ARM64_VHE
-	bool "Enable support for Virtualization Host Extensions (VHE)"
-	default y
-	help
-	  Virtualization Host Extensions (VHE) allow the kernel to run
-	  directly at EL2 (instead of EL1) on processors that support
-	  it. This leads to better performance for KVM, as they reduce
-	  the cost of the world switch.
-
-	  Selecting this option allows the VHE feature to be detected
-	  at runtime, and does not affect processors that do not
-	  implement this feature.
-
 endmenu
 
 menu "ARMv8.2 architectural features"

arch/arm64/include/asm/cpufeature.h

@@ -63,6 +63,23 @@ struct arm64_ftr_bits {
 	s64		safe_val; /* safe value for FTR_EXACT features */
 };
 
+/*
+ * Describe the early feature override to the core override code:
+ *
+ * @val			Values that are to be merged into the final
+ *			sanitised value of the register. Only the bitfields
+ *			set to 1 in @mask are valid
+ * @mask		Mask of the features that are overridden by @val
+ *
+ * A @mask field set to full-1 indicates that the corresponding field
+ * in @val is a valid override.
+ *
+ * A @mask field set to full-0 with the corresponding @val field set
+ * to full-0 denotes that this field has no override
+ *
+ * A @mask field set to full-0 with the corresponding @val field set
+ * to full-1 denotes thath this field has an invalid override.
+ */
 struct arm64_ftr_override {
 	u64		val;
 	u64		mask;

arch/arm64/kernel/cpufeature.c

@@ -808,6 +808,12 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 					reg->name,
 					ftrp->shift + ftrp->width - 1,
 					ftrp->shift, str, tmp);
+		} else if ((ftr_mask & reg->override->val) == ftr_mask) {
+			reg->override->val &= ~ftr_mask;
+			pr_warn("%s[%d:%d]: impossible override, ignored\n",
+				reg->name,
+				ftrp->shift + ftrp->width - 1,
+				ftrp->shift);
 		}
 
 		val = arm64_ftr_set_value(ftrp, val, ftr_new);
@@ -1616,7 +1622,6 @@ int get_cpu_with_amu_feat(void)
 }
 #endif
 
-#ifdef CONFIG_ARM64_VHE
 static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused)
 {
 	return is_kernel_in_hyp_mode();
@@ -1635,7 +1640,6 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
 	if (!alternative_is_applied(ARM64_HAS_VIRT_HOST_EXTN))
 		write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
 }
-#endif
 
 static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
 {
@@ -1838,7 +1842,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
 		.matches = has_no_hw_prefetch,
 	},
-#ifdef CONFIG_ARM64_VHE
 	{
 		.desc = "Virtualization Host Extensions",
 		.capability = ARM64_HAS_VIRT_HOST_EXTN,
@@ -1846,7 +1849,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = runs_at_el2,
 		.cpu_enable = cpu_copy_el2regs,
 	},
-#endif	/* CONFIG_ARM64_VHE */
 	{
 		.desc = "32-bit EL0 Support",
 		.capability = ARM64_HAS_32BIT_EL0,

arch/arm64/kernel/head.S

@@ -477,14 +477,13 @@ EXPORT_SYMBOL(kimage_vaddr)
  * booted in EL1 or EL2 respectively.
  */
 SYM_FUNC_START(init_kernel_el)
-	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
-	msr	sctlr_el1, x0
-
 	mrs	x0, CurrentEL
 	cmp	x0, #CurrentEL_EL2
 	b.eq	init_el2
 
 SYM_INNER_LABEL(init_el1, SYM_L_LOCAL)
+	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	msr	sctlr_el1, x0
 	isb
 	mov_q	x0, INIT_PSTATE_EL1
 	msr	spsr_el1, x0
@@ -504,9 +503,43 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 	msr	vbar_el2, x0
 	isb
 
+	/*
+	 * Fruity CPUs seem to have HCR_EL2.E2H set to RES1,
+	 * making it impossible to start in nVHE mode. Is that
+	 * compliant with the architecture? Absolutely not!
+	 */
+	mrs	x0, hcr_el2
+	and	x0, x0, #HCR_E2H
+	cbz	x0, 1f
+
+	/* Switching to VHE requires a sane SCTLR_EL1 as a start */
+	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	msr_s	SYS_SCTLR_EL12, x0
+
+	/*
+	 * Force an eret into a helper "function", and let it return
+	 * to our original caller... This makes sure that we have
+	 * initialised the basic PSTATE state.
+	 */
+	mov	x0, #INIT_PSTATE_EL2
+	msr	spsr_el1, x0
+	adr	x0, __cpu_stick_to_vhe
+	msr	elr_el1, x0
+	eret
+
+1:
+	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	msr	sctlr_el1, x0
+
 	msr	elr_el2, lr
 	mov	w0, #BOOT_CPU_MODE_EL2
 	eret
+
+__cpu_stick_to_vhe:
+	mov	x0, #HVC_VHE_RESTART
+	hvc	#0
+	mov	x0, #BOOT_CPU_MODE_EL2
+	ret
 SYM_FUNC_END(init_kernel_el)
 
 /*

arch/arm64/kernel/hyp-stub.S

@@ -27,12 +27,12 @@ SYM_CODE_START(__hyp_stub_vectors)
 	ventry	el2_fiq_invalid			// FIQ EL2t
 	ventry	el2_error_invalid		// Error EL2t
 
-	ventry	el2_sync_invalid		// Synchronous EL2h
+	ventry	elx_sync			// Synchronous EL2h
 	ventry	el2_irq_invalid			// IRQ EL2h
 	ventry	el2_fiq_invalid			// FIQ EL2h
 	ventry	el2_error_invalid		// Error EL2h
 
-	ventry	el1_sync			// Synchronous 64-bit EL1
+	ventry	elx_sync			// Synchronous 64-bit EL1
 	ventry	el1_irq_invalid			// IRQ 64-bit EL1
 	ventry	el1_fiq_invalid			// FIQ 64-bit EL1
 	ventry	el1_error_invalid		// Error 64-bit EL1
@@ -45,7 +45,7 @@ SYM_CODE_END(__hyp_stub_vectors)
 
 	.align 11
 
-SYM_CODE_START_LOCAL(el1_sync)
+SYM_CODE_START_LOCAL(elx_sync)
 	cmp	x0, #HVC_SET_VECTORS
 	b.ne	1f
 	msr	vbar_el2, x1
@@ -71,7 +71,7 @@ SYM_CODE_START_LOCAL(el1_sync)
 
 9:	mov	x0, xzr
 	eret
-SYM_CODE_END(el1_sync)
+SYM_CODE_END(elx_sync)
 
 // nVHE? No way! Give me the real thing!
 SYM_CODE_START_LOCAL(mutate_to_vhe)
@@ -225,7 +225,6 @@ SYM_FUNC_END(__hyp_reset_vectors)
  * Entry point to switch to VHE if deemed capable
  */
 SYM_FUNC_START(switch_to_vhe)
-#ifdef CONFIG_ARM64_VHE
 	// Need to have booted at EL2
 	adr_l	x1, __boot_cpu_mode
 	ldr	w0, [x1]
@@ -241,6 +240,5 @@ SYM_FUNC_START(switch_to_vhe)
 	mov	x0, #HVC_VHE_RESTART
 	hvc	#0
 1:
-#endif
 	ret
 SYM_FUNC_END(switch_to_vhe)

arch/arm64/kernel/idreg-override.c

@@ -25,14 +25,26 @@ struct ftr_set_desc {
 	struct {
 		char			name[FTR_DESC_FIELD_LEN];
 		u8			shift;
+		bool			(*filter)(u64 val);
 	} 				fields[];
 };
 
+static bool __init mmfr1_vh_filter(u64 val)
+{
+	/*
+	 * If we ever reach this point while running VHE, we're
+	 * guaranteed to be on one of these funky, VHE-stuck CPUs. If
+	 * the user was trying to force nVHE on us, proceed with
+	 * attitude adjustment.
+	 */
+	return !(is_kernel_in_hyp_mode() && val == 0);
+}
+
 static const struct ftr_set_desc mmfr1 __initconst = {
 	.name		= "id_aa64mmfr1",
 	.override	= &id_aa64mmfr1_override,
 	.fields		= {
-	        { "vh", ID_AA64MMFR1_VHE_SHIFT },
+		{ "vh", ID_AA64MMFR1_VHE_SHIFT, mmfr1_vh_filter },
 		{}
 	},
 };
@@ -124,6 +136,18 @@ static void __init match_options(const char *cmdline)
 			if (find_field(cmdline, regs[i], f, &v))
 				continue;
 
+			/*
+			 * If an override gets filtered out, advertise
+			 * it by setting the value to 0xf, but
+			 * clearing the mask... Yes, this is fragile.
+			 */
+			if (regs[i]->fields[f].filter &&
+			    !regs[i]->fields[f].filter(v)) {
+				regs[i]->override->val  |= mask;
+				regs[i]->override->mask &= ~mask;
+				continue;
+			}
+
 			regs[i]->override->val  &= ~mask;
 			regs[i]->override->val  |= (v << shift) & mask;
 			regs[i]->override->mask |= mask;