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Re: [Qemu-ppc] [PATCH v2] spapr: fallback to raw mode if best compat mod
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PATCH v2] spapr: fallback to raw mode if best compat mode cannot be set during CAS |
Date: |
Tue, 29 Aug 2017 17:38:00 +1000 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Thu, Aug 17, 2017 at 01:23:50PM +0200, Greg Kurz wrote:
> KVM PR doesn't allow to set a compat mode. This causes ppc_set_compat_all()
> to fail and we return H_HARDWARE to the guest right away.
>
> This is excessive: even if we favor compat mode since commit 152ef803ceb19,
> we should at least fallback to raw mode if the guest supports it.
>
> This patch modifies cas_check_pvr() so that it also reports that the real
> PVR was found in the table supplied by the guest. Note that this is only
> makes sense if raw mode isn't explicitely disabled (ie, the user didn't
> set the machine "max-cpu-compat" property). If this is the case, we can
> simply ignore ppc_set_compat_all() failures, and let the guest run in raw
> mode.
>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> v2: - initialize raw_mode_supported to silent patchew
I hesitated about this, because making guest visible changes based on
host abilities can get really messy. However we already have a bunch
of things like that in CAS, and we already migrate the compatibility
state, so I think it should be ok.
Applied to ppc-for-2.11.
> ---
> hw/ppc/spapr_hcall.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 07b3da8dc4cd..2f4c4f59e110 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1441,7 +1441,8 @@ static target_ulong h_signal_sys_reset(PowerPCCPU *cpu,
> }
>
> static uint32_t cas_check_pvr(sPAPRMachineState *spapr, PowerPCCPU *cpu,
> - target_ulong *addr, Error **errp)
> + target_ulong *addr, bool *raw_mode_supported,
> + Error **errp)
> {
> bool explicit_match = false; /* Matched the CPU's real PVR */
> uint32_t max_compat = spapr->max_compat_pvr;
> @@ -1481,6 +1482,8 @@ static uint32_t cas_check_pvr(sPAPRMachineState *spapr,
> PowerPCCPU *cpu,
> return 0;
> }
>
> + *raw_mode_supported = explicit_match;
> +
> /* Parsing finished */
> trace_spapr_cas_pvr(cpu->compat_pvr, explicit_match, best_compat);
>
> @@ -1499,8 +1502,9 @@ static target_ulong
> h_client_architecture_support(PowerPCCPU *cpu,
> sPAPROptionVector *ov1_guest, *ov5_guest, *ov5_cas_old, *ov5_updates;
> bool guest_radix;
> Error *local_err = NULL;
> + bool raw_mode_supported = false;
>
> - cas_pvr = cas_check_pvr(spapr, cpu, &addr, &local_err);
> + cas_pvr = cas_check_pvr(spapr, cpu, &addr, &raw_mode_supported,
> &local_err);
> if (local_err) {
> error_report_err(local_err);
> return H_HARDWARE;
> @@ -1510,8 +1514,14 @@ static target_ulong
> h_client_architecture_support(PowerPCCPU *cpu,
> if (cpu->compat_pvr != cas_pvr) {
> ppc_set_compat_all(cas_pvr, &local_err);
> if (local_err) {
> - error_report_err(local_err);
> - return H_HARDWARE;
> + /* We fail to set compat mode (likely because running with KVM
> PR),
> + * but maybe we can fallback to raw mode if the guest supports
> it.
> + */
> + if (!raw_mode_supported) {
> + error_report_err(local_err);
> + return H_HARDWARE;
> + }
> + local_err = NULL;
> }
> }
>
>
--
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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