On 06.08.2013, at 06:23, Paul Mackerras wrote:
> When we are running a PR KVM guest on POWER8, we have to disable the
> new POWER8 feature of taking interrupts with relocation on, that is,
> of taking interrupts without disabling the MMU, because the SLB does
> not contain the normal kernel SLB entries while in the guest.
> Currently we disable relocation-on interrupts when a PR guest is
> created, and leave it disabled until there are no more PR guests in
> existence.
>
> This defers the disabling of relocation-on interrupts until the first
It would've been nice to see the original patch on kvm-ppc@vger.
> time a PR KVM guest vcpu is run. The reason is that in future we will
> support both PR and HV guests in the same kernel, and this will avoid
> disabling relocation-on interrupts unnecessarily for guests which turn
> out to be HV guests, as we will not know at VM creation time whether
> it will be a PR or a HV guest.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
> ---
> arch/powerpc/include/asm/kvm_host.h | 1 +
> arch/powerpc/kvm/book3s_pr.c | 71 ++++++++++++++++++++++++++-----------
> 2 files changed, 52 insertions(+), 20 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 4d83972..c012db2 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -264,6 +264,7 @@ struct kvm_arch {
> #endif /* CONFIG_KVM_BOOK3S_64_HV */
> #ifdef CONFIG_KVM_BOOK3S_PR
> struct mutex hpt_mutex;
> + bool relon_disabled;
> #endif
> #ifdef CONFIG_PPC_BOOK3S_64
> struct list_head spapr_tce_tables;
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 5b06a70..2759ddc 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1197,6 +1197,47 @@ void kvmppc_core_vcpu_free(struct kvm_vcpu *vcpu)
> kmem_cache_free(kvm_vcpu_cache, vcpu);
> }
>
> +/*
> + * On POWER8, we have to disable relocation-on interrupts while
> + * we are in the guest, since the guest doesn't have the normal
> + * kernel SLB contents. Since disabling relocation-on interrupts
> + * is a fairly heavy-weight operation, we do it once when starting
> + * the first guest vcpu and leave it disabled until the last guest
> + * has been destroyed.
> + */
> +static unsigned int kvm_global_user_count = 0;
> +static DEFINE_SPINLOCK(kvm_global_user_count_lock);
> +
> +static void disable_relon_interrupts(struct kvm *kvm)
> +{
> + mutex_lock(&kvm->lock);
> + if (!kvm->arch.relon_disabled) {
> + if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
Is this the same as the endianness setting rtas call? If so, would a PR guest in an HV guest that provides only endianness setting but no relocation-on setting confuse any of this code?
Alex
> + spin_lock(&kvm_global_user_count_lock);
> + if (++kvm_global_user_count == 1)
> + pSeries_disable_reloc_on_exc();
> + spin_unlock(&kvm_global_user_count_lock);
> + }
> + /* order disabling above with setting relon_disabled */
> + smp_mb();
> + kvm->arch.relon_disabled = true;
> + }
> + mutex_unlock(&kvm->lock);
> +}
> +
> +static void enable_relon_interrupts(struct kvm *kvm)
> +{
> + if (kvm->arch.relon_disabled &&
> + firmware_has_feature(FW_FEATURE_SET_MODE)) {
> + spin_lock(&kvm_global_user_count_lock);
> + BUG_ON(kvm_global_user_count == 0);
> + if (--kvm_global_user_count == 0)
> + pSeries_enable_reloc_on_exc();
> + spin_unlock(&kvm_global_user_count_lock);
> + }
> + kvm->arch.relon_disabled = false;
> +}
> +
> int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> {
> int ret;
> @@ -1234,6 +1275,9 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> goto out;
> }
>
> + if (!vcpu->kvm->arch.relon_disabled)
> + disable_relon_interrupts(vcpu->kvm);
> +
> /* Save FPU state in stack */
> if (current->thread.regs->msr & MSR_FP)
> giveup_fpu(current);
> @@ -1400,9 +1444,6 @@ void kvmppc_core_flush_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> }
>
> -static unsigned int kvm_global_user_count = 0;
> -static DEFINE_SPINLOCK(kvm_global_user_count_lock);
> -
> int kvmppc_core_init_vm(struct kvm *kvm)
> {
> #ifdef CONFIG_PPC64
> @@ -1411,28 +1452,18 @@ int kvmppc_core_init_vm(struct kvm *kvm)
> #endif
> mutex_init(&kvm->arch.hpt_mutex);
>
> - if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
> - spin_lock(&kvm_global_user_count_lock);
> - if (++kvm_global_user_count == 1)
> - pSeries_disable_reloc_on_exc();
> - spin_unlock(&kvm_global_user_count_lock);
> - }
> + /*
> + * If we don't have relocation-on interrupts at all,
> + * then we can consider them to be already disabled.
> + */
> + kvm->arch.relon_disabled = !firmware_has_feature(FW_FEATURE_SET_MODE);
> +
> return 0;
> }
>
> void kvmppc_core_destroy_vm(struct kvm *kvm)
> {
> -#ifdef CONFIG_PPC64
> - WARN_ON(!list_empty(&kvm->arch.spapr_tce_tables));
> -#endif
> -
> - if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
> - spin_lock(&kvm_global_user_count_lock);
> - BUG_ON(kvm_global_user_count == 0);
> - if (--kvm_global_user_count == 0)
> - pSeries_enable_reloc_on_exc();
> - spin_unlock(&kvm_global_user_count_lock);
> - }
> + enable_relon_interrupts(kvm);
> }
>
> static int kvmppc_book3s_init(void)
> --
> 1.8.3.1
>
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