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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v11 1/2] vmx: VT-d posted-interrupt core logic handling
This is the core logic handling for VT-d posted-interrupts. Basically it
deals with how and when to update posted-interrupts during the following
scenarios:
- vCPU is preempted
- vCPU is slept
- vCPU is blocked
When vCPU is preempted/slept, we update the posted-interrupts during
scheduling by introducing two new architecutral scheduler hooks:
vmx_pi_switch_from() and vmx_pi_switch_to(). When vCPU is blocked, we
introduce a new architectural hook: arch_vcpu_block() to update
posted-interrupts descriptor.
Besides that, before VM-entry, we will make sure the 'NV' filed is set
to 'posted_intr_vector' and the vCPU is not in any blocking lists, which
is needed when vCPU is running in non-root mode. The reason we do this check
is because we change the posted-interrupts descriptor in vcpu_block(),
however, we don't change it back in vcpu_unblock() or when vcpu_block()
directly returns due to event delivery (in fact, we don't need to do it
in the two places, that is why we do it before VM-Entry).
When we handle the lazy context switch for the following two scenarios:
- Preempted by a tasklet, which uses in an idle context.
- the prev vcpu is in offline and no new available vcpus in run queue.
We don't change the 'SN' bit in posted-interrupt descriptor, this
may incur spurious PI notification events, but since PI notification
event is only sent when 'ON' is clear, and once the PI notificatoin
is sent, ON is set by hardware, hence no more notification events
before 'ON' is clear. Besides that, spurious PI notification events are
going to happen from time to time in Xen hypervisor, such as, when
guests trap to Xen and PI notification event happens, there is
nothing Xen actually needs to do about it, the interrupts will be
delivered to guest atht the next time we do a VMENTRY.
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Kevin Tian <kevin.tian@xxxxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
CC: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Suggested-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
Suggested-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Suggested-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
v11:
- Add ASSERT() in vmx_vcpu_block()
- Add some comments in vmx_pi_switch_from()
- Remove some comments which should have been removed when the
related code was removed during v9 -> v10
- Rename 'vmx_pi_state_to_normal' to 'vmx_pi_do_resume'
- Coding style
- Make arch_vcpu_block() a macro
- Make 'pi_wakeup_vector' static
- Move hook 'vcpu_block' to 'struct hvm_vcpu'
- Initial hook 'vcpu_block' when assigning the first pci device
and zap it on removal of the last device
- Save pointer to the block list lock instead of the processor
id in 'struct arch_vmx_struct'
- Implement the following functions as hooks, so we
can elimilate lots of checkings and spinlocks in scheduling
related code path, which is good for performance.
vmx_pi_switch_from
vmx_pi_switch_to
vmx_pi_do_resume
v10:
- Check iommu_intpost first
- Remove pointless checking of has_hvm_container_vcpu(v)
- Rename 'vmx_pi_state_change' to 'vmx_pi_state_to_normal'
- Since vcpu_unblock() doesn't acquire 'pi_blocked_vcpu_lock', we
don't need use another list to save the vCPUs with 'ON' set, just
directly call vcpu_unblock(v).
v9:
- Remove arch_vcpu_block_cancel() and arch_vcpu_wake_prepare()
- Add vmx_pi_state_change() and call it before VM Entry
v8:
- Remove the lazy context switch handling for PI state transition
- Change PI state in vcpu_block() and do_poll() when the vCPU
is going to be blocked
v7:
- Merge [PATCH v6 16/18] vmx: Add some scheduler hooks for VT-d posted
interrupts
and "[PATCH v6 14/18] vmx: posted-interrupt handling when vCPU is blocked"
into this patch, so it is self-contained and more convenient
for code review.
- Make 'pi_blocked_vcpu' and 'pi_blocked_vcpu_lock' static
- Coding style
- Use per_cpu() instead of this_cpu() in pi_wakeup_interrupt()
- Move ack_APIC_irq() to the beginning of pi_wakeup_interrupt()
- Rename 'pi_ctxt_switch_from' to 'ctxt_switch_prepare'
- Rename 'pi_ctxt_switch_to' to 'ctxt_switch_cancel'
- Use 'has_hvm_container_vcpu' instead of 'is_hvm_vcpu'
- Use 'spin_lock' and 'spin_unlock' when the interrupt has been
already disabled.
- Rename arch_vcpu_wake_prepare to vmx_vcpu_wake_prepare
- Define vmx_vcpu_wake_prepare in xen/arch/x86/hvm/hvm.c
- Call .pi_ctxt_switch_to() __context_switch() instead of directly
calling vmx_post_ctx_switch_pi() in vmx_ctxt_switch_to()
- Make .pi_block_cpu unsigned int
- Use list_del() instead of list_del_init()
- Coding style
One remaining item in v7:
Jan has concern about calling vcpu_unblock() in vmx_pre_ctx_switch_pi(),
need Dario or George's input about this.
v6:
- Add two static inline functions for pi context switch
- Fix typos
v5:
- Rename arch_vcpu_wake to arch_vcpu_wake_prepare
- Make arch_vcpu_wake_prepare() inline for ARM
- Merge the ARM dummy hook with together
- Changes to some code comments
- Leave 'pi_ctxt_switch_from' and 'pi_ctxt_switch_to' NULL if
PI is disabled or the vCPU is not in HVM
- Coding style
v4:
- Newly added
Changlog for "vmx: posted-interrupt handling when vCPU is blocked"
v6:
- Fix some typos
- Ack the interrupt right after the spin_unlock in pi_wakeup_interrupt()
v4:
- Use local variables in pi_wakeup_interrupt()
- Remove vcpu from the blocked list when pi_desc.on==1, this
- avoid kick vcpu multiple times.
- Remove tasklet
v3:
- This patch is generated by merging the following three patches in v2:
[RFC v2 09/15] Add a new per-vCPU tasklet to wakeup the blocked vCPU
[RFC v2 10/15] vmx: Define two per-cpu variables
[RFC v2 11/15] vmx: Add a global wake-up vector for VT-d Posted-Interrupts
- rename 'vcpu_wakeup_tasklet' to 'pi_vcpu_wakeup_tasklet'
- Move the definition of 'pi_vcpu_wakeup_tasklet' to 'struct arch_vmx_struct'
- rename 'vcpu_wakeup_tasklet_handler' to 'pi_vcpu_wakeup_tasklet_handler'
- Make pi_wakeup_interrupt() static
- Rename 'blocked_vcpu_list' to 'pi_blocked_vcpu_list'
- move 'pi_blocked_vcpu_list' to 'struct arch_vmx_struct'
- Rename 'blocked_vcpu' to 'pi_blocked_vcpu'
- Rename 'blocked_vcpu_lock' to 'pi_blocked_vcpu_lock'
xen/arch/x86/hvm/vmx/vmcs.c | 2 +
xen/arch/x86/hvm/vmx/vmx.c | 179 ++++++++++++++++++++++++++++++++++++
xen/common/schedule.c | 4 +
xen/drivers/passthrough/vtd/iommu.c | 2 +
xen/include/asm-arm/domain.h | 2 +
xen/include/asm-x86/hvm/hvm.h | 5 +
xen/include/asm-x86/hvm/vmx/vmcs.h | 14 +++
xen/include/asm-x86/hvm/vmx/vmx.h | 4 +
8 files changed, 212 insertions(+)
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index edd4c8d..2e535de 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -676,6 +676,8 @@ int vmx_cpu_up(void)
if ( cpu_has_vmx_vpid )
vpid_sync_all();
+ vmx_pi_per_cpu_init(cpu);
+
return 0;
}
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 7917fb7..d60c0d6 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -83,7 +83,140 @@ static int vmx_msr_write_intercept(unsigned int msr,
uint64_t msr_content);
static void vmx_invlpg_intercept(unsigned long vaddr);
static int vmx_vmfunc_intercept(struct cpu_user_regs *regs);
+/*
+ * We maintain a per-CPU linked-list of vCPUs, so in PI wakeup
+ * handler we can find which vCPU should be woken up.
+ */
+static DEFINE_PER_CPU(struct list_head, pi_blocked_vcpu);
+static DEFINE_PER_CPU(spinlock_t, pi_blocked_vcpu_lock);
+
uint8_t __read_mostly posted_intr_vector;
+static uint8_t __read_mostly pi_wakeup_vector;
+
+void vmx_pi_per_cpu_init(unsigned int cpu)
+{
+ INIT_LIST_HEAD(&per_cpu(pi_blocked_vcpu, cpu));
+ spin_lock_init(&per_cpu(pi_blocked_vcpu_lock, cpu));
+}
+
+static void vmx_vcpu_block(struct vcpu *v)
+{
+ unsigned long flags;
+ unsigned int dest;
+
+ struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
+
+ ASSERT(v->arch.hvm_vmx.pi_block_list_lock == NULL);
+
+ /* The vCPU is blocking, we need to add it to one of the per-cpu lists. */
+ v->arch.hvm_vmx.pi_block_list_lock =
+ &per_cpu(pi_blocked_vcpu_lock, v->processor);
+
+ spin_lock_irqsave(v->arch.hvm_vmx.pi_block_list_lock, flags);
+ list_add_tail(&v->arch.hvm_vmx.pi_blocked_vcpu_list,
+ &per_cpu(pi_blocked_vcpu, v->processor));
+ spin_unlock_irqrestore(v->arch.hvm_vmx.pi_block_list_lock, flags);
+
+ ASSERT(!pi_test_sn(pi_desc));
+
+ dest = cpu_physical_id(v->processor);
+
+ ASSERT(pi_desc->ndst ==
+ (x2apic_enabled ? dest: MASK_INSR(dest, PI_xAPIC_NDST_MASK)));
+
+ write_atomic(&pi_desc->nv, pi_wakeup_vector);
+}
+
+static void vmx_pi_switch_from(struct vcpu *v)
+{
+ struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
+
+ if ( test_bit(_VPF_blocked, &v->pause_flags) )
+ return;
+
+ /*
+ * The vCPU has been preempted or went to sleep. We don't
+ * need to send notification event to a runnable or sleeping
+ * vcpu, the interrupt information will be delivered to it
+ * before VM-ENTRY when the vcpu is scheduled to run next time.
+ */
+ pi_set_sn(pi_desc);
+}
+
+static void vmx_pi_switch_to(struct vcpu *v)
+{
+ struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
+
+ write_atomic(&pi_desc->ndst, x2apic_enabled ?
+ cpu_physical_id(v->processor) :
+ MASK_INSR(cpu_physical_id(v->processor), PI_xAPIC_NDST_MASK));
+
+ /*
+ * The vCPU is going to run, we need to clear 'SN' to
+ * make it accept notification event when interrupts
+ * will being posted for it.
+ */
+ pi_clear_sn(pi_desc);
+}
+
+static void vmx_pi_do_resume(struct vcpu *v)
+{
+ unsigned long flags;
+ spinlock_t *pi_block_list_lock;
+ struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
+
+ ASSERT(!test_bit(_VPF_blocked, &v->pause_flags));
+
+ /*
+ * Set 'NV' field back to posted_intr_vector, so the
+ * Posted-Interrupts can be delivered to the vCPU when
+ * it is running in non-root mode.
+ */
+ if ( pi_desc->nv != posted_intr_vector )
+ write_atomic(&pi_desc->nv, posted_intr_vector);
+
+ /* The vCPU is not on any blocking list. */
+ pi_block_list_lock = v->arch.hvm_vmx.pi_block_list_lock;
+ if ( pi_block_list_lock == NULL )
+ return;
+
+ spin_lock_irqsave(pi_block_list_lock, flags);
+
+ /*
+ * v->arch.hvm_vmx.pi_block_list_lock == NULL here means the vCPU was
+ * removed from the blocking list while we are acquiring the lock.
+ */
+ if ( v->arch.hvm_vmx.pi_block_list_lock != NULL )
+ {
+ list_del(&v->arch.hvm_vmx.pi_blocked_vcpu_list);
+ v->arch.hvm_vmx.pi_block_list_lock = NULL;
+ }
+
+ spin_unlock_irqrestore(pi_block_list_lock, flags);
+}
+
+/* This function is called when pcidevs_lock is held */
+void vmx_pi_hooks_reassign(struct domain *source, struct domain *target)
+{
+ if (!iommu_intpost)
+ return;
+
+ if ( has_hvm_container_domain(source) &&
+ source->arch.hvm_domain.vmx.vcpu_block && !has_arch_pdevs(source) ) {
+ source->arch.hvm_domain.vmx.vcpu_block = NULL;
+ source->arch.hvm_domain.vmx.pi_switch_from = NULL;
+ source->arch.hvm_domain.vmx.pi_switch_to = NULL;
+ source->arch.hvm_domain.vmx.pi_do_resume = NULL;
+ }
+
+ if ( has_hvm_container_domain(target) &&
+ !target->arch.hvm_domain.vmx.vcpu_block && has_arch_pdevs(target) ) {
+ target->arch.hvm_domain.vmx.vcpu_block = vmx_vcpu_block;
+ target->arch.hvm_domain.vmx.pi_switch_from = vmx_pi_switch_from;
+ target->arch.hvm_domain.vmx.pi_switch_to = vmx_pi_switch_to;
+ target->arch.hvm_domain.vmx.pi_do_resume = vmx_pi_do_resume;
+ }
+}
static int vmx_domain_initialise(struct domain *d)
{
@@ -112,6 +245,10 @@ static int vmx_vcpu_initialise(struct vcpu *v)
spin_lock_init(&v->arch.hvm_vmx.vmcs_lock);
+ INIT_LIST_HEAD(&v->arch.hvm_vmx.pi_blocked_vcpu_list);
+
+ v->arch.hvm_vmx.pi_block_list_lock = NULL;
+
v->arch.schedule_tail = vmx_do_resume;
v->arch.ctxt_switch_from = vmx_ctxt_switch_from;
v->arch.ctxt_switch_to = vmx_ctxt_switch_to;
@@ -740,6 +877,8 @@ static void vmx_ctxt_switch_from(struct vcpu *v)
vmx_save_guest_msrs(v);
vmx_restore_host_msrs();
vmx_save_dr(v);
+ if (v->domain->arch.hvm_domain.vmx.pi_switch_from)
+ v->domain->arch.hvm_domain.vmx.pi_switch_from(v);
}
static void vmx_ctxt_switch_to(struct vcpu *v)
@@ -752,6 +891,8 @@ static void vmx_ctxt_switch_to(struct vcpu *v)
vmx_restore_guest_msrs(v);
vmx_restore_dr(v);
+ if (v->domain->arch.hvm_domain.vmx.pi_switch_to)
+ v->domain->arch.hvm_domain.vmx.pi_switch_to(v);
}
@@ -2010,6 +2151,38 @@ static struct hvm_function_table __initdata
vmx_function_table = {
.altp2m_vcpu_emulate_vmfunc = vmx_vcpu_emulate_vmfunc,
};
+/* Handle VT-d posted-interrupt when VCPU is blocked. */
+static void pi_wakeup_interrupt(struct cpu_user_regs *regs)
+{
+ struct arch_vmx_struct *vmx, *tmp;
+ spinlock_t *lock = &per_cpu(pi_blocked_vcpu_lock, smp_processor_id());
+ struct list_head *blocked_vcpus =
+ &per_cpu(pi_blocked_vcpu, smp_processor_id());
+
+ ack_APIC_irq();
+ this_cpu(irq_count)++;
+
+ spin_lock(lock);
+
+ /*
+ * XXX: The length of the list depends on how many vCPU is current
+ * blocked on this specific pCPU. This may hurt the interrupt latency
+ * if the list grows to too many entries.
+ */
+ list_for_each_entry_safe(vmx, tmp, blocked_vcpus, pi_blocked_vcpu_list)
+ {
+ if ( pi_test_on(&vmx->pi_desc) )
+ {
+ list_del(&vmx->pi_blocked_vcpu_list);
+ ASSERT(vmx->pi_block_list_lock == lock);
+ vmx->pi_block_list_lock = NULL;
+ vcpu_unblock(container_of(vmx, struct vcpu, arch.hvm_vmx));
+ }
+ }
+
+ spin_unlock(lock);
+}
+
/* Handle VT-d posted-interrupt when VCPU is running. */
static void pi_notification_interrupt(struct cpu_user_regs *regs)
{
@@ -2096,7 +2269,10 @@ const struct hvm_function_table * __init start_vmx(void)
if ( cpu_has_vmx_posted_intr_processing )
{
if ( iommu_intpost )
+ {
alloc_direct_apic_vector(&posted_intr_vector,
pi_notification_interrupt);
+ alloc_direct_apic_vector(&pi_wakeup_vector, pi_wakeup_interrupt);
+ }
else
alloc_direct_apic_vector(&posted_intr_vector,
event_check_interrupt);
}
@@ -3574,6 +3750,9 @@ void vmx_vmenter_helper(const struct cpu_user_regs *regs)
struct hvm_vcpu_asid *p_asid;
bool_t need_flush;
+ if (curr->domain->arch.hvm_domain.vmx.pi_do_resume)
+ curr->domain->arch.hvm_domain.vmx.pi_do_resume(curr);
+
if ( !cpu_has_vmx_vpid )
goto out;
if ( nestedhvm_vcpu_in_guestmode(curr) )
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index d121896..2d87021 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -802,6 +802,8 @@ void vcpu_block(void)
set_bit(_VPF_blocked, &v->pause_flags);
+ arch_vcpu_block(v);
+
/* Check for events /after/ blocking: avoids wakeup waiting race. */
if ( local_events_need_delivery() )
{
@@ -839,6 +841,8 @@ static long do_poll(struct sched_poll *sched_poll)
v->poll_evtchn = -1;
set_bit(v->vcpu_id, d->poll_mask);
+ arch_vcpu_block(v);
+
#ifndef CONFIG_X86 /* set_bit() implies mb() on x86 */
/* Check for events /after/ setting flags: avoids wakeup waiting race. */
smp_mb();
diff --git a/xen/drivers/passthrough/vtd/iommu.c
b/xen/drivers/passthrough/vtd/iommu.c
index ec31c6b..fb47d29 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2293,6 +2293,8 @@ static int reassign_device_ownership(
pdev->domain = target;
}
+ vmx_pi_hooks_reassign(source, target);
+
return ret;
}
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index aa7f283..37afa80 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -310,6 +310,8 @@ static inline void free_vcpu_guest_context(struct
vcpu_guest_context *vgc)
xfree(vgc);
}
+static inline void arch_vcpu_block(struct vcpu *v) {}
+
#endif /* __ASM_DOMAIN_H__ */
/*
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index b9d893d..4590456 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -565,6 +565,11 @@ const char *hvm_efer_valid(const struct vcpu *v, uint64_t
value,
signed int cr0_pg);
unsigned long hvm_cr4_guest_reserved_bits(const struct vcpu *v, bool_t
restore);
+#define arch_vcpu_block(v) ({ \
+ if ( (v)->domain->arch.hvm_domain.vmx.vcpu_block ) \
+ (v)->domain->arch.hvm_domain.vmx.vcpu_block((v)); \
+})
+
#endif /* __ASM_X86_HVM_HVM_H__ */
/*
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h
b/xen/include/asm-x86/hvm/vmx/vmcs.h
index d1496b8..b7cc900 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -77,6 +77,11 @@ struct vmx_domain {
unsigned long apic_access_mfn;
/* VMX_DOMAIN_* */
unsigned int status;
+
+ void (*vcpu_block) (struct vcpu *);
+ void (*pi_switch_from) (struct vcpu *v);
+ void (*pi_switch_to) (struct vcpu *v);
+ void (*pi_do_resume) (struct vcpu *v);
};
struct pi_desc {
@@ -160,6 +165,15 @@ struct arch_vmx_struct {
struct page_info *vmwrite_bitmap;
struct page_info *pml_pg;
+
+ struct list_head pi_blocked_vcpu_list;
+
+ /*
+ * Before it is blocked, vCPU is added to the per-cpu list.
+ * VT-d engine can send wakeup notification event to the
+ * pCPU and wakeup the related vCPU.
+ */
+ spinlock_t *pi_block_list_lock;
};
int vmx_create_vmcs(struct vcpu *v);
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h
b/xen/include/asm-x86/hvm/vmx/vmx.h
index 1719965..baaaa53 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -563,6 +563,10 @@ int alloc_p2m_hap_data(struct p2m_domain *p2m);
void free_p2m_hap_data(struct p2m_domain *p2m);
void p2m_init_hap_data(struct p2m_domain *p2m);
+void vmx_pi_per_cpu_init(unsigned int cpu);
+
+void vmx_pi_hooks_reassign(struct domain *source, struct domain *target);
+
/* EPT violation qualifications definitions */
#define _EPT_READ_VIOLATION 0
#define EPT_READ_VIOLATION (1UL<<_EPT_READ_VIOLATION)
--
2.1.0
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