Subject: [PATCH 01/26] KVM: arm64: Check advertised Stage-2 page size capability

From: Marc Zyngier <[email-masked]>
Date: Wed, 22 Apr 2020 13:00:25 +0100

With ARMv8.5-GTG, the hardware (or more likely a hypervisor) can
advertise the supported Stage-2 page sizes.

Let's check this at boot time.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/include/asm/kvm_host.h |  2 +-
 arch/arm64/include/asm/sysreg.h   |  3 +++
 arch/arm64/kernel/cpufeature.c    |  8 +++++++
 arch/arm64/kvm/reset.c            | 40 ++++++++++++++++++++++++++++---
 virt/kvm/arm/arm.c                |  4 +---
 5 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 32c8a675e5a4a..7dd8fefa6aecd 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -670,7 +670,7 @@ static inline int kvm_arm_have_ssbd(void)
 void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
 void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
 
-void kvm_set_ipa_limit(void);
+int kvm_set_ipa_limit(void);
 
 #define __KVM_HAVE_ARCH_VM_ALLOC
 struct kvm *kvm_arch_alloc_vm(void);
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index ebc6224328318..5d10c9148e844 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -686,6 +686,9 @@
 #define ID_AA64ZFR0_SVEVER_SVE2		0x1
 
 /* id_aa64mmfr0 */
+#define ID_AA64MMFR0_TGRAN4_2_SHIFT	40
+#define ID_AA64MMFR0_TGRAN64_2_SHIFT	36
+#define ID_AA64MMFR0_TGRAN16_2_SHIFT	32
 #define ID_AA64MMFR0_TGRAN4_SHIFT	28
 #define ID_AA64MMFR0_TGRAN64_SHIFT	24
 #define ID_AA64MMFR0_TGRAN16_SHIFT	20
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9fac745aa7bb2..9892a845d06c9 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -208,6 +208,14 @@ static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
+	/*
+	 * Page size not being supported at Stage-2 are not fatal. You
+	 * just give up KVM if PAGE_SIZE isn't supported there. Go fix
+	 * your favourite nesting hypervisor.
+	 */
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN4_2_SHIFT, 4, 1),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN64_2_SHIFT, 4, 1),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN16_2_SHIFT, 4, 1),
 	/*
 	 * We already refuse to boot CPUs that don't support our configured
 	 * page size, so we can only detect mismatches for a page size other
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 30b7ea680f66c..241db35a7ef4f 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/errno.h>
+#include <linux/bitfield.h>
 #include <linux/kernel.h>
 #include <linux/kvm_host.h>
 #include <linux/kvm.h>
@@ -340,11 +341,42 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
-void kvm_set_ipa_limit(void)
+int kvm_set_ipa_limit(void)
 {
-	unsigned int ipa_max, pa_max, va_max, parange;
+	unsigned int ipa_max, pa_max, va_max, parange, tgran_2;
+	u64 mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
 
-	parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 0x7;
+	/*
+	 * Check with ARMv8.5-GTG that our PAGE_SIZE is supported at
+	 * Stage-2. If not, things will stop very quickly.
+	 */
+	switch (PAGE_SIZE) {
+	default:
+	case SZ_4K:
+		tgran_2 = ID_AA64MMFR0_TGRAN4_2_SHIFT;
+		break;
+	case SZ_16K:
+		tgran_2 = ID_AA64MMFR0_TGRAN16_2_SHIFT;
+		break;
+	case SZ_64K:
+		tgran_2 = ID_AA64MMFR0_TGRAN64_2_SHIFT;
+		break;
+	}
+
+	switch (FIELD_GET(0xFUL << tgran_2, mmfr0)) {
+	default:
+	case 1:
+		kvm_err("PAGE_SIZE not supported at Stage-2, giving up\n");
+		return -EINVAL;
+	case 0:
+		kvm_debug("PAGE_SIZE supported at Stage-2 (default)\n");
+		break;
+	case 2:
+		kvm_debug("PAGE_SIZE supported at Stage-2 (advertised)\n");
+		break;
+	}
+
+	parange = mmfr0 & 0x7;
 	pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
 
 	/* Clamp the IPA limit to the PA size supported by the kernel */
@@ -378,6 +410,8 @@ void kvm_set_ipa_limit(void)
 	     "KVM IPA limit (%d bit) is smaller than default size\n", ipa_max);
 	kvm_ipa_limit = ipa_max;
 	kvm_info("IPA Size Limit: %dbits\n", kvm_ipa_limit);
+
+	return 0;
 }
 
 /*
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 48d0ec44ad77e..53b3ba9173ba7 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1387,9 +1387,7 @@ static inline void hyp_cpu_pm_exit(void)
 
 static int init_common_resources(void)
 {
-	kvm_set_ipa_limit();
-
-	return 0;
+	return kvm_set_ipa_limit();
 }
 
 static int init_subsystems(void)
-- 
2.26.1

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