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[PULL 46/46] target/arm: Implement ARMv8.1-VMID16 extension

From: Peter Maydell
Subject: [PULL 46/46] target/arm: Implement ARMv8.1-VMID16 extension
Date: Thu, 13 Feb 2020 14:41:45 +0000

The ARMv8.1-VMID16 extension extends the VMID from 8 bits to 16 bits:

 * the ID_AA64MMFR1_EL1.VMIDBits field specifies whether the VMID is
   8 or 16 bits
 * the VMID field in VTTBR_EL2 is extended to 16 bits
 * VTCR_EL2.VS lets the guest specify whether to use the full 16 bits,
   or use the backwards-compatible 8 bits

For QEMU implementing this is trivial:
 * we do not track VMIDs in TLB entries, so we never use the VMID field
 * we treat any write to VTTBR_EL2, not just a change to the VMID field
   bits, as a "possible VMID change" that causes us to throw away TLB
   entries, so that code doesn't need changing
 * we allow the guest to read/write the VTCR_EL2.VS bit already

So all that's missing is the ID register part: report that we support
VMID16 in our 'max' CPU.

Signed-off-by: Peter Maydell <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Message-id: address@hidden
 target/arm/cpu64.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 1359564c554..f0d98bc79d1 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -674,6 +674,7 @@ static void aarch64_max_initfn(Object *obj)
         t = FIELD_DP64(t, ID_AA64MMFR1, LO, 1);
         t = FIELD_DP64(t, ID_AA64MMFR1, VH, 1);
         t = FIELD_DP64(t, ID_AA64MMFR1, PAN, 2); /* ATS1E1 */
+        t = FIELD_DP64(t, ID_AA64MMFR1, VMIDBITS, 2); /* VMID16 */
         cpu->isar.id_aa64mmfr1 = t;
         t = cpu->isar.id_aa64mmfr2;

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