On Fri, Apr 26, 2013 at 07:53:38PM -0500, Scott Wood wrote:
> KVM core expects arch code to acquire the srcu lock when calling
> gfn_to_memslot and similar functions.
>
> Signed-off-by: Scott Wood <scottwood@xxxxxxxxxxxxx>
> ---
> arch/powerpc/kvm/44x_tlb.c | 5 +++++
> arch/powerpc/kvm/booke.c | 19 +++++++++++++++++++
> arch/powerpc/kvm/e500_mmu.c | 5 +++++
> 3 files changed, 29 insertions(+)
>
> diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
> index 5dd3ab4..ed03854 100644
> --- a/arch/powerpc/kvm/44x_tlb.c
> +++ b/arch/powerpc/kvm/44x_tlb.c
> @@ -441,6 +441,7 @@ int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
> struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
> struct kvmppc_44x_tlbe *tlbe;
> unsigned int gtlb_index;
> + int idx;
>
> gtlb_index = kvmppc_get_gpr(vcpu, ra);
> if (gtlb_index >= KVM44x_GUEST_TLB_SIZE) {
> @@ -473,6 +474,8 @@ int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
> return EMULATE_FAIL;
> }
>
> + idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> if (tlbe_is_host_safe(vcpu, tlbe)) {
> gva_t eaddr;
> gpa_t gpaddr;
> @@ -489,6 +492,8 @@ int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
> kvmppc_mmu_map(vcpu, eaddr, gpaddr, gtlb_index);
> }
>
> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
> +
> trace_kvm_gtlb_write(gtlb_index, tlbe->tid, tlbe->word0, tlbe->word1,
> tlbe->word2);
>
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 1020119..506c87d 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -832,6 +832,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> {
> int r = RESUME_HOST;
> int s;
> + int idx = 0; /* silence bogus uninitialized warning */
> + bool need_srcu = false;
>
> /* update before a new last_exit_type is rewritten */
> kvmppc_update_timing_stats(vcpu);
> @@ -847,6 +849,20 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> run->exit_reason = KVM_EXIT_UNKNOWN;
> run->ready_for_interrupt_injection = 1;
>
> + /*
> + * Don't get the srcu lock unconditionally, because kvm_ppc_pv()
> + * can call kvm_vcpu_block(), and kvm_ppc_pv() is shared with
> + * book3s, so dropping the srcu lock there would be awkward.
> + */
> + switch (exit_nr) {
> + case BOOKE_INTERRUPT_ITLB_MISS:
> + case BOOKE_INTERRUPT_DTLB_MISS:
> + need_srcu = true;
> + }
This is not good practice (codepaths should either hold srcu or not hold
it, unconditionally).
Can you give more details of the issue? (not obvious)
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