[PATCH 12/14] KVM: arm64: Advertise FEAT_ECV when possible

[Marc Zyngier]

We can advertise support for FEAT_ECV if supported on the HW as
long as we limit it to the basic trap bits, and not advertise
CNTPOFF_EL2 support, even if the host has it (the short story
being that CNTPOFF_EL2 is not virtualisable).

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/nested.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 5ec5acb6310e9..d55c296fcb27a 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -848,14 +848,16 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
 		break;
 
 	case SYS_ID_AA64MMFR0_EL1:
-		/* Hide ECV, ExS, Secure Memory */
-		val &= ~(ID_AA64MMFR0_EL1_EVC		|
-			 ID_AA64MMFR0_EL1_EXS		|
+		/* Hide ExS, Secure Memory */
+		val &= ~(ID_AA64MMFR0_EL1_EXS		|
 			 ID_AA64MMFR0_EL1_TGRAN4_2	|
 			 ID_AA64MMFR0_EL1_TGRAN16_2	|
 			 ID_AA64MMFR0_EL1_TGRAN64_2	|
 			 ID_AA64MMFR0_EL1_SNSMEM);
 
+		/* Hide CNTPOFF if present */
+		val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64MMFR0_EL1, ECV, IMP);
+
 		/* Disallow unsupported S2 page sizes */
 		switch (PAGE_SIZE) {
 		case SZ_64K:
-- 
2.39.2