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Re: [Qemu-ppc] [PATCH v4 3/3] spapr/rtas: do not reset the MSR in stop-s
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PATCH v4 3/3] spapr/rtas: do not reset the MSR in stop-self command |
Date: |
Mon, 27 Nov 2017 18:19:54 +1100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Nov 24, 2017 at 08:05:50AM +0100, Cédric Le Goater wrote:
> When a CPU is stopped with the 'stop-self' RTAS call, its state
> 'halted' is switched to 1 and, in this case, the MSR is not taken into
> account anymore in the cpu_has_work() routine. Only the pending
> hardware interrupts are checked with their LPCR:PECE* enablement bit.
>
> The CPU is now also protected from the decrementer interrupt by the
> LPCR:PECE* bits which are disabled in the 'stop-self' RTAS
> call. Reseting the MSR is pointless.
>
> Signed-off-by: Cédric Le Goater <address@hidden>
> Reviewed-by: David Gibson <address@hidden>
Applied to ppc-for-2.12.
> ---
> hw/ppc/spapr_rtas.c | 10 ----------
> 1 file changed, 10 deletions(-)
>
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 858adb1bf3a9..4bb939d3d111 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -206,16 +206,6 @@ static void rtas_stop_self(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>
> cs->halted = 1;
> qemu_cpu_kick(cs);
> - /*
> - * While stopping a CPU, the guest calls H_CPPR which
> - * effectively disables interrupts on XICS level.
> - * However decrementer interrupts in TCG can still
> - * wake the CPU up so here we disable interrupts in MSR
> - * as well.
> - * As rtas_start_cpu() resets the whole MSR anyway, there is
> - * no need to bother with specific bits, we just clear it.
> - */
> - env->msr = 0;
>
> /* Disable Power-saving mode Exit Cause exceptions for the CPU.
> * This could deliver an interrupt on a dying CPU and crash the
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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