[RFC PATCH 18/18] x86: request TLB flush to slave CPU using NMI

Tomoki Sekiyama
2012-06-28T06:09:48Z

For slave CPUs, it is inapropriate to request TLB flush using IPI.
because the IPI may be sent to a KVM guest when the slave CPU is running
the guest with direct interrupt routing.

Instead, it registers a TLB flush request in per-cpu bitmask and send a NMI
to interrupt execution of the guest. Then, NMI handler will check the
requests and handles the requests.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---

arch/x86/include/asm/mmu.h | 7 +++++
arch/x86/kvm/x86.c | 26 ++++++++++++++++++
arch/x86/mm/tlb.c | 63 ++++++++++++++++++++++++++++++++++++++++----
3 files changed, 90 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 5f55e69..25af7f1 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -29,4 +29,11 @@ static inline void leave_mm(int cpu)
}
#endif

+#ifdef CONFIG_SLAVE_CPU
+typedef void(slave_tlbf_notifier_t)(unsigned int cpu, unsigned int sender);
+extern void register_slave_tlbf_notifier(slave_tlbf_notifier_t *f,
+ unsigned int cpu);
+extern void __smp_invalidate_tlb(unsigned int sender);
+#endif
+
#endif /* _ASM_X86_MMU_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 90307f0..6ede776 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2636,6 +2636,7 @@ static int kvm_set_guest_paused(struct kvm_vcpu *vcpu)

#ifdef CONFIG_SLAVE_CPU

+static void add_slave_tlbf_request(unsigned int cpu, unsigned int sender);
static int kvm_arch_kicked_by_nmi(unsigned int cmd, struct pt_regs *regs);

static int kvm_arch_vcpu_ioctl_set_slave_cpu(struct kvm_vcpu *vcpu,
@@ -2663,6 +2664,7 @@ static int kvm_arch_vcpu_ioctl_set_slave_cpu(struct kvm_vcpu *vcpu,
if (r)
goto out;
BUG_ON(!cpu_slave(slave));
+ register_slave_tlbf_notifier(add_slave_tlbf_request, slave);
}

vcpu->arch.slave_cpu = slave;
@@ -5331,6 +5333,9 @@ static void process_nmi(struct kvm_vcpu *vcpu)
/* vcpu currently running on each slave CPU */
static DEFINE_PER_CPU(struct kvm_vcpu *, slave_vcpu);

+/* bitmask to store TLB flush sender sent to each CPU */
+static DEFINE_PER_CPU(unsigned long, slave_tlb_flush_requests);
+
void kvm_get_slave_cpu_mask(struct kvm *kvm, struct cpumask *mask)
{
int i;
@@ -5341,6 +5346,25 @@ void kvm_get_slave_cpu_mask(struct kvm *kvm, struct cpumask *mask)
cpumask_set_cpu(vcpu->arch.slave_cpu, mask);
}

+static void add_slave_tlbf_request(unsigned int cpu, unsigned int sender)
+{
+ unsigned long *mask = &per_cpu(slave_tlb_flush_requests, cpu);
+
+ atomic_set_mask(1 << sender, mask);
+ apic->send_IPI_mask(get_cpu_mask(cpu), NMI_VECTOR);
+}
+
+static void handle_slave_tlb_flush_requests(int cpu)
+{
+ unsigned int sender;
+ unsigned long *mask = &per_cpu(slave_tlb_flush_requests, cpu);
+
+ for_each_set_bit(sender, mask, NUM_INVALIDATE_TLB_VECTORS) {
+ atomic_clear_mask(1 << sender, mask);
+ __smp_invalidate_tlb(sender);
+ }
+}
+
static int kvm_arch_kicked_by_nmi(unsigned int cmd, struct pt_regs *regs)
{
struct kvm_vcpu *vcpu;
@@ -5349,6 +5373,8 @@ static int kvm_arch_kicked_by_nmi(unsigned int cmd, struct pt_regs *regs)
if (!cpu_slave(cpu))
return NMI_DONE;

+ handle_slave_tlb_flush_requests(cpu);
+
/* if called from NMI handler after VM exit, no need to prevent run */
vcpu = __this_cpu_read(slave_vcpu);
if (!vcpu || vcpu->mode == OUTSIDE_GUEST_MODE || kvm_is_in_guest())
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5e57e11..c53bd43 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -12,6 +12,7 @@
#include <asm/cache.h>
#include <asm/apic.h>
#include <asm/uv/uv.h>
+#include <asm/cpu.h>

DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate)
= { &init_mm, 0, };
@@ -55,6 +56,30 @@ static union smp_flush_state flush_state[NUM_INVALIDATE_TLB_VECTORS];

static DEFINE_PER_CPU_READ_MOSTLY(int, tlb_vector_offset);

+#ifdef CONFIG_SLAVE_CPU
+
+static DEFINE_PER_CPU(slave_tlbf_notifier_t *, slave_tlbf_notifier);
+
+void register_slave_tlbf_notifier(slave_tlbf_notifier_t *f, unsigned int cpu)
+{
+ per_cpu(slave_tlbf_notifier, cpu) = f;
+}
+EXPORT_SYMBOL(register_slave_tlbf_notifier);
+
+void request_slave_tlb_flush(const struct cpumask *mask, unsigned int sender)
+{
+ int cpu;
+ slave_tlbf_notifier_t *f;
+
+ for_each_cpu_and(cpu, mask, cpu_slave_mask) {
+ f = per_cpu(slave_tlbf_notifier, cpu);
+ if (f)
+ f(cpu, sender);
+ }
+}
+
+#endif
+
/*
* We cannot call mmdrop() because we are in interrupt context,
* instead update mm->cpu_vm_mask.
@@ -131,17 +156,22 @@ asmlinkage
#endif
void smp_invalidate_interrupt(struct pt_regs *regs)
{
- unsigned int cpu;
unsigned int sender;
- union smp_flush_state *f;

- cpu = smp_processor_id();
/*
* orig_rax contains the negated interrupt vector.
* Use that to determine where the sender put the data.
*/
sender = ~regs->orig_ax - INVALIDATE_TLB_VECTOR_START;
- f = &flush_state[sender];
+ __smp_invalidate_tlb(sender);
+ ack_APIC_irq();
+ inc_irq_stat(irq_tlb_count);
+}
+
+void __smp_invalidate_tlb(unsigned int sender)
+{
+ union smp_flush_state *f = &flush_state[sender];
+ unsigned int cpu = smp_processor_id();

if (!cpumask_test_cpu(cpu, to_cpumask(f->flush_cpumask)))
goto out;
@@ -163,13 +193,13 @@ void smp_invalidate_interrupt(struct pt_regs *regs)
} else
leave_mm(cpu);
}
+
out:
- ack_APIC_irq();
smp_mb__before_clear_bit();
cpumask_clear_cpu(cpu, to_cpumask(f->flush_cpumask));
smp_mb__after_clear_bit();
- inc_irq_stat(irq_tlb_count);
}
+EXPORT_SYMBOL_GPL(__smp_invalidate_tlb);

static void flush_tlb_others_ipi(const struct cpumask *cpumask,
struct mm_struct *mm, unsigned long va)
@@ -191,8 +221,29 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
* We have to send the IPI only to
* CPUs affected.
*/
+#ifdef CONFIG_SLAVE_CPU
+ cpumask_var_t ipi_mask;
+
+ request_slave_tlb_flush(to_cpumask(f->flush_cpumask), sender);
+
+ /* send IPI only to online CPUs */
+ if (!alloc_cpumask_var(&ipi_mask, GFP_KERNEL))
+ /* insufficient memory... send IPI to all CPUs */
+ apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
+ INVALIDATE_TLB_VECTOR_START + sender);
+ else {
+ cpumask_and(ipi_mask, to_cpumask(f->flush_cpumask),
+ cpu_online_mask);
+ request_slave_tlb_flush(to_cpumask(f->flush_cpumask),
+ sender);
+ apic->send_IPI_mask(ipi_mask,
+ INVALIDATE_TLB_VECTOR_START + sender);
+ free_cpumask_var(ipi_mask);
+ }
+#else
apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
INVALIDATE_TLB_VECTOR_START + sender);
+#endif

while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
cpu_relax();