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authorPaul Mackerras <paulus@samba.org>2014-01-08 21:25:20 +1100
committerAlexander Graf <agraf@suse.de>2014-01-27 16:00:59 +0100
commite0b7ec058c0eb7ba8d5d937d81de2bd16db6970e (patch)
tree32b266bf4e3c497ab0a306731c01761b2dde11ce /arch/powerpc/kvm/book3s_hv.c
parenteee7ff9d2cc0eaaa00496bdf4193144104c7dc63 (diff)
KVM: PPC: Book3S HV: Align physical and virtual CPU thread numbers
On a threaded processor such as POWER7, we group VCPUs into virtual cores and arrange that the VCPUs in a virtual core run on the same physical core. Currently we don't enforce any correspondence between virtual thread numbers within a virtual core and physical thread numbers. Physical threads are allocated starting at 0 on a first-come first-served basis to runnable virtual threads (VCPUs). POWER8 implements a new "msgsndp" instruction which guest kernels can use to interrupt other threads in the same core or sub-core. Since the instruction takes the destination physical thread ID as a parameter, it becomes necessary to align the physical thread IDs with the virtual thread IDs, that is, to make sure virtual thread N within a virtual core always runs on physical thread N. This means that it's possible that thread 0, which is where we call __kvmppc_vcore_entry, may end up running some other vcpu than the one whose task called kvmppc_run_core(), or it may end up running no vcpu at all, if for example thread 0 of the virtual core is currently executing in userspace. However, we do need thread 0 to be responsible for switching the MMU -- a previous version of this patch that had other threads switching the MMU was found to be responsible for occasional memory corruption and machine check interrupts in the guest on POWER7 machines. To accommodate this, we no longer pass the vcpu pointer to __kvmppc_vcore_entry, but instead let the assembly code load it from the PACA. Since the assembly code will need to know the kvm pointer and the thread ID for threads which don't have a vcpu, we move the thread ID into the PACA and we add a kvm pointer to the virtual core structure. In the case where thread 0 has no vcpu to run, it still calls into kvmppc_hv_entry in order to do the MMU switch, and then naps until either its vcpu is ready to run in the guest, or some other thread needs to exit the guest. In the latter case, thread 0 jumps to the code that switches the MMU back to the host. This control flow means that now we switch the MMU before loading any guest vcpu state. Similarly, on guest exit we now save all the guest vcpu state before switching the MMU back to the host. This has required substantial code movement, making the diff rather large. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de>
Diffstat (limited to 'arch/powerpc/kvm/book3s_hv.c')
-rw-r--r--arch/powerpc/kvm/book3s_hv.c46
1 files changed, 17 insertions, 29 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 7e1813ceabc1..7da53cd215db 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -990,6 +990,8 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm,
init_waitqueue_head(&vcore->wq);
vcore->preempt_tb = TB_NIL;
vcore->lpcr = kvm->arch.lpcr;
+ vcore->first_vcpuid = core * threads_per_core;
+ vcore->kvm = kvm;
}
kvm->arch.vcores[core] = vcore;
kvm->arch.online_vcores++;
@@ -1003,6 +1005,7 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm,
++vcore->num_threads;
spin_unlock(&vcore->lock);
vcpu->arch.vcore = vcore;
+ vcpu->arch.ptid = vcpu->vcpu_id - vcore->first_vcpuid;
vcpu->arch.cpu_type = KVM_CPU_3S_64;
kvmppc_sanity_check(vcpu);
@@ -1066,7 +1069,7 @@ static void kvmppc_end_cede(struct kvm_vcpu *vcpu)
}
}
-extern int __kvmppc_vcore_entry(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
+extern void __kvmppc_vcore_entry(void);
static void kvmppc_remove_runnable(struct kvmppc_vcore *vc,
struct kvm_vcpu *vcpu)
@@ -1140,15 +1143,16 @@ static void kvmppc_start_thread(struct kvm_vcpu *vcpu)
tpaca = &paca[cpu];
tpaca->kvm_hstate.kvm_vcpu = vcpu;
tpaca->kvm_hstate.kvm_vcore = vc;
- tpaca->kvm_hstate.napping = 0;
+ tpaca->kvm_hstate.ptid = vcpu->arch.ptid;
vcpu->cpu = vc->pcpu;
smp_wmb();
#if defined(CONFIG_PPC_ICP_NATIVE) && defined(CONFIG_SMP)
- if (vcpu->arch.ptid) {
+ if (cpu != smp_processor_id()) {
#ifdef CONFIG_KVM_XICS
xics_wake_cpu(cpu);
#endif
- ++vc->n_woken;
+ if (vcpu->arch.ptid)
+ ++vc->n_woken;
}
#endif
}
@@ -1205,10 +1209,10 @@ static int on_primary_thread(void)
*/
static void kvmppc_run_core(struct kvmppc_vcore *vc)
{
- struct kvm_vcpu *vcpu, *vcpu0, *vnext;
+ struct kvm_vcpu *vcpu, *vnext;
long ret;
u64 now;
- int ptid, i, need_vpa_update;
+ int i, need_vpa_update;
int srcu_idx;
struct kvm_vcpu *vcpus_to_update[threads_per_core];
@@ -1246,25 +1250,6 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
}
/*
- * Assign physical thread IDs, first to non-ceded vcpus
- * and then to ceded ones.
- */
- ptid = 0;
- vcpu0 = NULL;
- list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) {
- if (!vcpu->arch.ceded) {
- if (!ptid)
- vcpu0 = vcpu;
- vcpu->arch.ptid = ptid++;
- }
- }
- if (!vcpu0)
- goto out; /* nothing to run; should never happen */
- list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list)
- if (vcpu->arch.ceded)
- vcpu->arch.ptid = ptid++;
-
- /*
* Make sure we are running on thread 0, and that
* secondary threads are offline.
*/
@@ -1280,15 +1265,19 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
kvmppc_create_dtl_entry(vcpu, vc);
}
+ /* Set this explicitly in case thread 0 doesn't have a vcpu */
+ get_paca()->kvm_hstate.kvm_vcore = vc;
+ get_paca()->kvm_hstate.ptid = 0;
+
vc->vcore_state = VCORE_RUNNING;
preempt_disable();
spin_unlock(&vc->lock);
kvm_guest_enter();
- srcu_idx = srcu_read_lock(&vcpu0->kvm->srcu);
+ srcu_idx = srcu_read_lock(&vc->kvm->srcu);
- __kvmppc_vcore_entry(NULL, vcpu0);
+ __kvmppc_vcore_entry();
spin_lock(&vc->lock);
/* disable sending of IPIs on virtual external irqs */
@@ -1303,7 +1292,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
vc->vcore_state = VCORE_EXITING;
spin_unlock(&vc->lock);
- srcu_read_unlock(&vcpu0->kvm->srcu, srcu_idx);
+ srcu_read_unlock(&vc->kvm->srcu, srcu_idx);
/* make sure updates to secondary vcpu structs are visible now */
smp_mb();
@@ -1411,7 +1400,6 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
if (!signal_pending(current)) {
if (vc->vcore_state == VCORE_RUNNING &&
VCORE_EXIT_COUNT(vc) == 0) {
- vcpu->arch.ptid = vc->n_runnable - 1;
kvmppc_create_dtl_entry(vcpu, vc);
kvmppc_start_thread(vcpu);
} else if (vc->vcore_state == VCORE_SLEEPING) {