Nicholas Piggin <npig...@gmail.com> writes:
> From: Suraj Jitindar Singh <sjitindarsi...@gmail.com>
>
> The POWER9 vCPU TLB management code assumes all threads in a core share
> a TLB, and that TLBIEL execued by one thread will invalidate TLBs for
> all threads. This is not the case for SMT8 capable POWER9 and POWER10
> (big core) processors, where the TLB is split between groups of threads.
> This results in TLB multi-hits, random data corruption, etc.
>
> Fix this by introducing cpu_first_tlb_thread_sibling etc., to determine
> which siblings share TLBs, and use that in the guest TLB flushing code.
>
> [npig...@gmail.com: add changelog and comment]
>
> Signed-off-by: Paul Mackerras <pau...@ozlabs.org>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Reviewed-by: Fabiano Rosas <faro...@linux.ibm.com>
> ---
> arch/powerpc/include/asm/cputhreads.h | 30 +++++++++++++++++++++++++++
> arch/powerpc/kvm/book3s_hv.c | 13 ++++++------
> arch/powerpc/kvm/book3s_hv_builtin.c | 2 +-
> arch/powerpc/kvm/book3s_hv_rm_mmu.c | 2 +-
> 4 files changed, 39 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/cputhreads.h
> b/arch/powerpc/include/asm/cputhreads.h
> index 98c8bd155bf9..b167186aaee4 100644
> --- a/arch/powerpc/include/asm/cputhreads.h
> +++ b/arch/powerpc/include/asm/cputhreads.h
> @@ -98,6 +98,36 @@ static inline int cpu_last_thread_sibling(int cpu)
> return cpu | (threads_per_core - 1);
> }
>
> +/*
> + * tlb_thread_siblings are siblings which share a TLB. This is not
> + * architected, is not something a hypervisor could emulate and a future
> + * CPU may change behaviour even in compat mode, so this should only be
> + * used on PowerNV, and only with care.
> + */
> +static inline int cpu_first_tlb_thread_sibling(int cpu)
> +{
> + if (cpu_has_feature(CPU_FTR_ARCH_300) && (threads_per_core == 8))
> + return cpu & ~0x6; /* Big Core */
> + else
> + return cpu_first_thread_sibling(cpu);
> +}
> +
> +static inline int cpu_last_tlb_thread_sibling(int cpu)
> +{
> + if (cpu_has_feature(CPU_FTR_ARCH_300) && (threads_per_core == 8))
> + return cpu | 0x6; /* Big Core */
> + else
> + return cpu_last_thread_sibling(cpu);
> +}
> +
> +static inline int cpu_tlb_thread_sibling_step(void)
> +{
> + if (cpu_has_feature(CPU_FTR_ARCH_300) && (threads_per_core == 8))
> + return 2; /* Big Core */
> + else
> + return 1;
> +}
> +
> static inline u32 get_tensr(void)
> {
> #ifdef CONFIG_BOOKE
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 28a80d240b76..0a8398a63f80 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -2657,7 +2657,7 @@ static void radix_flush_cpu(struct kvm *kvm, int cpu,
> struct kvm_vcpu *vcpu)
> cpumask_t *cpu_in_guest;
> int i;
>
> - cpu = cpu_first_thread_sibling(cpu);
> + cpu = cpu_first_tlb_thread_sibling(cpu);
> if (nested) {
> cpumask_set_cpu(cpu, &nested->need_tlb_flush);
> cpu_in_guest = &nested->cpu_in_guest;
> @@ -2671,9 +2671,10 @@ static void radix_flush_cpu(struct kvm *kvm, int cpu,
> struct kvm_vcpu *vcpu)
> * the other side is the first smp_mb() in kvmppc_run_core().
> */
> smp_mb();
> - for (i = 0; i < threads_per_core; ++i)
> - if (cpumask_test_cpu(cpu + i, cpu_in_guest))
> - smp_call_function_single(cpu + i, do_nothing, NULL, 1);
> + for (i = cpu; i <= cpu_last_tlb_thread_sibling(cpu);
> + i += cpu_tlb_thread_sibling_step())
> + if (cpumask_test_cpu(i, cpu_in_guest))
> + smp_call_function_single(i, do_nothing, NULL, 1);
> }
>
> static void kvmppc_prepare_radix_vcpu(struct kvm_vcpu *vcpu, int pcpu)
> @@ -2704,8 +2705,8 @@ static void kvmppc_prepare_radix_vcpu(struct kvm_vcpu
> *vcpu, int pcpu)
> */
> if (prev_cpu != pcpu) {
> if (prev_cpu >= 0 &&
> - cpu_first_thread_sibling(prev_cpu) !=
> - cpu_first_thread_sibling(pcpu))
> + cpu_first_tlb_thread_sibling(prev_cpu) !=
> + cpu_first_tlb_thread_sibling(pcpu))
> radix_flush_cpu(kvm, prev_cpu, vcpu);
> if (nested)
> nested->prev_cpu[vcpu->arch.nested_vcpu_id] = pcpu;
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c
> b/arch/powerpc/kvm/book3s_hv_builtin.c
> index 7a0e33a9c980..3edc25c89092 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -800,7 +800,7 @@ void kvmppc_check_need_tlb_flush(struct kvm *kvm, int
> pcpu,
> * Thus we make all 4 threads use the same bit.
> */
> if (cpu_has_feature(CPU_FTR_ARCH_300))
> - pcpu = cpu_first_thread_sibling(pcpu);
> + pcpu = cpu_first_tlb_thread_sibling(pcpu);
>
> if (nested)
> need_tlb_flush = &nested->need_tlb_flush;
> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> index 7af7c70f1468..407dbf21bcbc 100644
> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> @@ -67,7 +67,7 @@ static int global_invalidates(struct kvm *kvm)
> * so use the bit for the first thread to represent the core.
> */
> if (cpu_has_feature(CPU_FTR_ARCH_300))
> - cpu = cpu_first_thread_sibling(cpu);
> + cpu = cpu_first_tlb_thread_sibling(cpu);
> cpumask_clear_cpu(cpu, &kvm->arch.need_tlb_flush);
> }
