On 04.03.2016 06:35, David Gibson wrote:
> When a Power cpu with 64-bit hash MMU has it's hash page table (HPT)
> pointer updated by a write to the SDR1 register we need to update some
> derived variables. Likewise, when the cpu is configured for an external
> HPT (one not in the guest memory space) some derived variables need to be
> updated.
>
> Currently the logic for this is (partially) duplicated in ppc_store_sdr1()
> and in spapr_cpu_reset(). In future we're going to need it in some other
> places, so make some common helpers for this update.
>
> In addition the new ppc_hash64_set_external_hpt() helper also updates
> SDR1 in KVM - it's not updated by the normal runtime KVM <-> qemu CPU
> synchronization. In a sense this belongs logically in the
> ppc_hash64_set_sdr1() helper, but that is called from
> kvm_arch_get_registers() so can't itself call cpu_synchronize_state()
> without infinite recursion. In practice this doesn't matter because
> the only other caller is TCG specific.
>
> Currently there aren't situations where updating SDR1 at runtime in KVM
> matters, but there are going to be in future.
>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> hw/ppc/spapr.c | 13 ++-----------
> target-ppc/kvm.c | 15 +++++++++++++++
> target-ppc/kvm_ppc.h | 6 ++++++
> target-ppc/mmu-hash64.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> target-ppc/mmu-hash64.h | 6 ++++++
> target-ppc/mmu_helper.c | 13 ++++++-------
> 6 files changed, 77 insertions(+), 18 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e9d4abf..a88e3af 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1196,17 +1196,8 @@ static void spapr_cpu_reset(void *opaque)
>
> env->spr[SPR_HIOR] = 0;
>
> - env->external_htab = (uint8_t *)spapr->htab;
> - env->htab_base = -1;
> - /*
> - * htab_mask is the mask used to normalize hash value to PTEG index.
> - * htab_shift is log2 of hash table size.
> - * We have 8 hpte per group, and each hpte is 16 bytes.
> - * ie have 128 bytes per hpte entry.
> - */
> - env->htab_mask = (1ULL << (spapr->htab_shift - 7)) - 1;
> - env->spr[SPR_SDR1] = (target_ulong)(uintptr_t)spapr->htab |
> - (spapr->htab_shift - 18);
> + ppc_hash64_set_external_hpt(cpu, spapr->htab, spapr->htab_shift,
> + &error_fatal);
> }
>
> static void spapr_create_nvram(sPAPRMachineState *spapr)
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index d67c169..99b3231 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -2537,3 +2537,18 @@ int kvmppc_enable_hwrng(void)
>
> return kvmppc_enable_hcall(kvm_state, H_RANDOM);
> }
> +
> +int kvmppc_update_sdr1(PowerPCCPU *cpu)
> +{
> + CPUState *cs = CPU(cpu);
> +
> + if (!kvm_enabled()) {
> + return 0; /* nothing to do */
> + }
Since you're updating more than SDR1 below ... Could you maybe add a
"assert(cs->kvm_vcpu_dirty)" here, just to make sure that nobody
accidentally ever calls this function without synchronizing the
registers first?
> + /* The normal KVM_PUT_RUNTIME_STATE doesn't include SDR1, which is
> + * why we need an explicit update for it. KVM_PUT_RESET_STATE is
> + * overkill, but this is a pretty rare operation, so it's simpler
> + * than writing a special purpose updater */
> + return kvm_arch_put_registers(cs, KVM_PUT_RESET_STATE);
> +}
That indeed looks like a big overkill ... what about extracting the
block from kvm_arch_put_registers() which sets the the "struct
kvm_sregs" via KVM_SET_SREGS into a separate function, and then call
that function here instead?
kvm_arch_put_registers() is IMHO way too big anyway, so separating some
code into external functions there would improve readability there, too.
Apart from that, the patch looks right to me.
Thomas
