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Re: [Qemu-ppc] [RFC 1/2] pseries: Split CAS PVR negotiation out into a s
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-ppc] [RFC 1/2] pseries: Split CAS PVR negotiation out into a separate function |
Date: |
Wed, 17 May 2017 10:55:52 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 17/05/2017 08:35, David Gibson wrote:
> Guests of the qemu machine type go through a feature negotiation process
> known as "client architecture support" (CAS) during early boot. This does
> a number of things, one of which is finding a CPU compatibility mode which
> can be supported by both guest and host.
>
> In fact the CPU negotiation is probably the single most complex part of the
> CAS process, so this splits it out into a helper function. We've recently
> made some mistakes in maintaining backward compatibility for old machine
> types here. Splitting this out will also make it easier to fix this.
>
> This also adds a possibly useful error message if the negotiation fails
> (i.e. if there is CPU mode that's suitable for both guest and host).
>
> Signed-off-by: David Gibson <address@hidden>
> ---
> hw/ppc/spapr_hcall.c | 43 +++++++++++++++++++++++++++----------------
> 1 file changed, 27 insertions(+), 16 deletions(-)
>
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 0d608d6..007ae8d 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1047,19 +1047,13 @@ static target_ulong h_signal_sys_reset(PowerPCCPU
> *cpu,
> }
> }
>
> -static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
> - sPAPRMachineState *spapr,
> - target_ulong opcode,
> - target_ulong *args)
> +static uint32_t cas_check_pvr(PowerPCCPU *cpu, target_ulong list,
> + Error **errp)
> {
> - target_ulong list = ppc64_phys_to_real(args[0]);
> - target_ulong ov_table;
> bool explicit_match = false; /* Matched the CPU's real PVR */
> uint32_t max_compat = cpu->max_compat;
> uint32_t best_compat = 0;
> int i;
> - sPAPROptionVector *ov1_guest, *ov5_guest, *ov5_cas_old, *ov5_updates;
> - bool guest_radix;
>
> /*
> * We scan the supplied table of PVRs looking for two things
> @@ -1090,26 +1084,43 @@ static target_ulong
> h_client_architecture_support(PowerPCCPU *cpu,
> /* We couldn't find a suitable compatibility mode, and either
> * the guest doesn't support "raw" mode for this CPU, or raw
> * mode is disabled because a maximum compat mode is set */
> - return H_HARDWARE;
> + error_setg(errp, "Couldn't negotiate a suitable PVR during CAS");
> + return 0;
> }
>
> /* Parsing finished */
> trace_spapr_cas_pvr(cpu->compat_pvr, explicit_match, best_compat);
>
> - /* Update CPUs */
> - if (cpu->compat_pvr != best_compat) {
> - Error *local_err = NULL;
> + return best_compat;
> +}
> +
> +static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
> + sPAPRMachineState *spapr,
> + target_ulong opcode,
> + target_ulong *args)
> +{
> + /* @ov_table points to the first option vector */
> + target_ulong ov_table = ppc64_phys_to_real(args[0]);
> + uint32_t cas_pvr;
> + sPAPROptionVector *ov1_guest, *ov5_guest, *ov5_cas_old, *ov5_updates;
> + bool guest_radix;
> + Error *local_err = NULL;
>
> - ppc_set_compat_all(best_compat, &local_err);
> + cas_pvr = cas_check_pvr(cpu, ov_table, &local_err);
> + if (local_err) {
> + error_report_err(local_err);
> + return H_HARDWARE;
> + }
> +
> + /* Update CPUs */
> + 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;
> }
> }
>
> - /* For the future use: here @ov_table points to the first option vector
> */
> - ov_table = list;
> -
I think there is a change here: now ov_table is always
ppc64_phys_to_real(args[0]), as it is not updated by cas_check() as list
was by h_client_architecture_support().
> ov1_guest = spapr_ovec_parse_vector(ov_table, 1);
> ov5_guest = spapr_ovec_parse_vector(ov_table, 5);
> if (spapr_ovec_test(ov5_guest, OV5_MMU_BOTH)) {
Laurent