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[Qemu-devel] [Bug 1723984] Re: ID_MMFR0 has an invalid value on aarch64


From: Peter Maydell
Subject: [Qemu-devel] [Bug 1723984] Re: ID_MMFR0 has an invalid value on aarch64 cpu (A57, A53)
Date: Tue, 17 Oct 2017 11:13:55 -0000

QEMU's behaviour in this case is matching the hardware. We claim to
model an r1p0 (based on the MIDR value we report), and for the r1p0 the
A53 and A57 reported the ID_MMFR0 as 0x10101105 -- this is documented in
the TRMs for that rev of the CPUs. r1p3 reports the 0x10201105 you
describe, but this isn't the rev of the CPU we claim to be.

In theory we could bump the rXpX but I'm not sure there's much point
unless it's causing a real problem (we'd need to check what else might
have changed between the two revisions).

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https://bugs.launchpad.net/bugs/1723984

Title:
  ID_MMFR0 has an invalid value on aarch64 cpu (A57, A53)

Status in QEMU:
  New

Bug description:
  The ID_MMFR0 register, accessed from aarch64 state as an invalid value:
  - ARM ARM v8 documentation (D7.2 General system control registers) described 
bits AuxReg[23:20] to be
    "In ARMv8-A the only permitted value is 0010"
  - Cortex A53 and Cortex A57 TRM describe the value to be 0x10201105, so 
AuxReg[23:20] is 0010 too
  - in QEMU target/arm/cpu64.c, the relevant value is
    cpu->id_mmfr0 = 0x10101105;

  The 1 should be changed to 2.

  Spotted & Tested on the following qemu revision:

  commit 48ae1f60d8c9a770e6da64407984d84e25253c69
  Merge: 78b62d3 b867eaa
  Author: Peter Maydell <address@hidden>
  Date:   Mon Oct 16 14:28:13 2017 +0100

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