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KVM: arm64: add workaround for Cortex-A57 erratum #852523

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When restoring the system register state for an AArch32 guest at EL2,
writes to DACR32_EL2 may not be correctly synchronised by Cortex-A57,
which can lead to the guest effectively running with junk in the DACR
and running into unexpected domain faults.

This patch works around the issue by re-ordering our restoration of the
AArch32 register aliases so that they happen before the AArch64 system
registers. Ensuring that the registers are restored in this order
guarantees that they will be correctly synchronised by the core.

Cc: <stable@vger.kernel.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Will Deacon 2015-09-14 16:06:03 +01:00 committed by Marc Zyngier
parent 0c0672922d
commit 43297dda0a
1 changed files with 3 additions and 1 deletions
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4
arch/arm64/kvm/hyp.S
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@ -745,6 +745,9 @@ ENTRY(__kvm_vcpu_run)
// Guest context
add x2, x0, #VCPU_CONTEXT
// We must restore the 32-bit state before the sysregs, thanks
// to Cortex-A57 erratum #852523.
restore_guest_32bit_state
bl __restore_sysregs
skip_debug_state x3, 1f
@ -752,7 +755,6 @@ ENTRY(__kvm_vcpu_run)
kern_hyp_va x3
bl __restore_debug
1:
restore_guest_32bit_state
restore_guest_regs
// That's it, no more messing around.