Subject: [PATCH v2 34/94] KVM: arm64: nv: Use ARMv8.5-GTG to advertise supported Stage-2 page sizes

From: Marc Zyngier <[email-masked]>
Date: Tue, 11 Feb 2020 17:48:38 +0000

ARMv8.5-GTG gives the opportunity to advertize the supported Stage-2
page sizes to hypervisors, and allow them to differ from the page sizes
supported at Stage-1.

As KVM cannot support guest Stage-2 page sizes that are smaller than
PAGE_SIZE (it would break the guest's isolation guarantees), let's use
this feature to let the guest know (assuming it has been told about
ARMv8.5-GTG).

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/include/asm/sysreg.h |  3 +++
 arch/arm64/kvm/nested.c         | 29 +++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 360ef9e8dfe4..a167219e42f4 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -701,6 +701,9 @@
 #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/kvm/nested.c b/arch/arm64/kvm/nested.c
index cecea8d91196..c40bf753ead9 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -95,6 +95,35 @@ void access_nested_id_reg(struct kvm_vcpu *v, struct sys_reg_params *p,
 		break;
 
 	case SYS_ID_AA64MMFR0_EL1:
+		/* Hide unsupported S2 page sizes */
+		switch (PAGE_SIZE) {
+		case SZ_64K:
+			val &= ~FEATURE(ID_AA64MMFR0_TGRAN16_2);
+			val |= FIELD_PREP(FEATURE(ID_AA64MMFR0_TGRAN16_2), 0b0001);
+			/* Fall through */
+		case SZ_16K:
+			val &= ~FEATURE(ID_AA64MMFR0_TGRAN4_2);
+			val |= FIELD_PREP(FEATURE(ID_AA64MMFR0_TGRAN4_2), 0b0001);
+			/* Fall through */
+		case SZ_4K:
+			/* Support everything */
+			break;
+		}
+		/* Advertize supported S2 page sizes */
+		switch (PAGE_SIZE) {
+		case SZ_4K:
+			val &= ~FEATURE(ID_AA64MMFR0_TGRAN4_2);
+			val |= FIELD_PREP(FEATURE(ID_AA64MMFR0_TGRAN4_2), 0b0010);
+			/* Fall through */
+		case SZ_16K:
+			val &= ~FEATURE(ID_AA64MMFR0_TGRAN16_2);
+			val |= FIELD_PREP(FEATURE(ID_AA64MMFR0_TGRAN16_2), 0b0010);
+			/* Fall through */
+		case SZ_64K:
+			val &= ~FEATURE(ID_AA64MMFR0_TGRAN64_2);
+			val |= FIELD_PREP(FEATURE(ID_AA64MMFR0_TGRAN64_2), 0b0010);
+			break;
+		}
 		/* Cap PARange to 40bits */
 		tmp = FIELD_GET(FEATURE(ID_AA64MMFR0_PARANGE), val);
 		if (tmp > 0b0010) {
-- 
2.20.1

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