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From: Peter Maydell <peter.maydell@linaro.org>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [PULL 01/29] target/arm: generate a custom MIDR for -cpu max
Date: Fri, 16 Aug 2019 14:16:51 +0100
Message-ID: <20190816131719.28244-2-peter.maydell@linaro.org> (raw)
In-Reply-To: <20190816131719.28244-1-peter.maydell@linaro.org>

From: Alex Bennée <alex.bennee@linaro.org>

While most features are now detected by probing the ID_* registers
kernels can (and do) use MIDR_EL1 for working out of they have to
apply errata. This can trip up warnings in the kernel as it tries to
work out if it should apply workarounds to features that don't
actually exist in the reported CPU type.

Avoid this problem by synthesising our own MIDR value.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190726113950.7499-1-alex.bennee@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h   |  6 ++++++
 target/arm/cpu64.c | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 94c990cddbd..67f2af0e169 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1611,6 +1611,12 @@ FIELD(V7M_FPCCR, ASPEN, 31, 1)
 /*
  * System register ID fields.
  */
+FIELD(MIDR_EL1, REVISION, 0, 4)
+FIELD(MIDR_EL1, PARTNUM, 4, 12)
+FIELD(MIDR_EL1, ARCHITECTURE, 16, 4)
+FIELD(MIDR_EL1, VARIANT, 20, 4)
+FIELD(MIDR_EL1, IMPLEMENTER, 24, 8)
+
 FIELD(ID_ISAR0, SWAP, 0, 4)
 FIELD(ID_ISAR0, BITCOUNT, 4, 4)
 FIELD(ID_ISAR0, BITFIELD, 8, 4)
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 1901997a064..ee55237a9b2 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -296,6 +296,25 @@ static void aarch64_max_initfn(Object *obj)
         uint32_t u;
         aarch64_a57_initfn(obj);
 
+        /*
+         * Reset MIDR so the guest doesn't mistake our 'max' CPU type for a real
+         * one and try to apply errata workarounds or use impdef features we
+         * don't provide.
+         * An IMPLEMENTER field of 0 means "reserved for software use";
+         * ARCHITECTURE must be 0xf indicating "v7 or later, check ID registers
+         * to see which features are present";
+         * the VARIANT, PARTNUM and REVISION fields are all implementation
+         * defined and we choose to define PARTNUM just in case guest
+         * code needs to distinguish this QEMU CPU from other software
+         * implementations, though this shouldn't be needed.
+         */
+        t = FIELD_DP64(0, MIDR_EL1, IMPLEMENTER, 0);
+        t = FIELD_DP64(t, MIDR_EL1, ARCHITECTURE, 0xf);
+        t = FIELD_DP64(t, MIDR_EL1, PARTNUM, 'Q');
+        t = FIELD_DP64(t, MIDR_EL1, VARIANT, 0);
+        t = FIELD_DP64(t, MIDR_EL1, REVISION, 0);
+        cpu->midr = t;
+
         t = cpu->isar.id_aa64isar0;
         t = FIELD_DP64(t, ID_AA64ISAR0, AES, 2); /* AES + PMULL */
         t = FIELD_DP64(t, ID_AA64ISAR0, SHA1, 1);
-- 
2.20.1



  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-16 13:16 [Qemu-devel] [PULL 00/29] target-arm queue Peter Maydell
2019-08-16 13:16 ` Peter Maydell [this message]
2019-08-16 13:16 ` [Qemu-devel] [PULL 02/29] hw/misc/zynq_slcr: use standard register definition Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 03/29] Set ENET_BD_BDU in I.MX FEC controller Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 04/29] target/arm: Factor out 'generate singlestep exception' function Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 05/29] target/arm: Fix routing of singlestep exceptions Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 06/29] target/arm: Pass in pc to thumb_insn_is_16bit Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 07/29] target/arm: Introduce pc_curr Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 08/29] target/arm: Introduce read_pc Peter Maydell
2019-08-16 13:16 ` [Qemu-devel] [PULL 09/29] target/arm: Introduce add_reg_for_lit Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 10/29] target/arm: Remove redundant s->pc & ~1 Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 11/29] target/arm: Replace s->pc with s->base.pc_next Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 12/29] target/arm: Replace offset with pc in gen_exception_insn Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 13/29] target/arm: Replace offset with pc in gen_exception_internal_insn Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 14/29] target/arm: Remove offset argument to gen_exception_bkpt_insn Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 15/29] target/arm: Use unallocated_encoding for aarch32 Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 16/29] target/arm: Remove helper_double_saturate Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 17/29] target/arm/cpu64: Ensure kvm really supports aarch64=off Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 18/29] target/arm/cpu: Ensure we can use the pmu with kvm Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 19/29] target/arm/helper: zcr: Add build bug next to value range assumption Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 20/29] target/arm/cpu: Use div-round-up to determine predicate register array size Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 21/29] target/arm/kvm64: Fix error returns Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 22/29] target/arm/kvm64: Move the get/put of fpsimd registers out Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 23/29] target/arm: Use tcg_gen_extract_i32 for shifter_out_im Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 24/29] target/arm: Use tcg_gen_deposit_i32 for PKHBT, PKHTB Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 25/29] target/arm: Remove redundant shift tests Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 26/29] target/arm: Use ror32 instead of open-coding the operation Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 27/29] target/arm: Use tcg_gen_rotri_i32 for gen_swap_half Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 28/29] target/arm: Simplify SMMLA, SMMLAR, SMMLS, SMMLSR Peter Maydell
2019-08-16 13:17 ` [Qemu-devel] [PULL 29/29] target/arm: Use tcg_gen_extrh_i64_i32 to extract the high word Peter Maydell
2019-08-16 17:02 ` [Qemu-devel] [PULL 00/29] target-arm queue Peter Maydell

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