[PART1 RFC v3 12/12] svm: Manage vcpu load/unload when enable AVIC

Suravee Suthikulpanit
2016-03-18T06:12:46Z

From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

When a vcpu is loaded/unloaded to a physical core, we need to update
host physical APIC ID information in the Physical APIC-ID table
accordingly.

Also, when vCPU is blocking/un-blocking (due to halt instruction),
we need to make sure that the is-running bit in set accordingly in the
physical APIC-ID table.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
arch/x86/kvm/svm.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 121 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d5418c3..c5e8100 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -35,6 +35,7 @@
#include <linux/trace_events.h>
#include <linux/slab.h>

+#include <asm/apic.h>
#include <asm/perf_event.h>
#include <asm/tlbflush.h>
#include <asm/desc.h>
@@ -1334,6 +1335,110 @@ free_avic:
return err;
}

+static int avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool is_load)
+{
+ int h_phy_apic_id;
+ u64 *entry, new_entry;
+ struct vcpu_svm *svm = to_svm(vcpu);
+ int ret = 0;
+
+ if (!svm_vcpu_avic_enabled(svm))
+ return 0;
+
+ if (!svm)
+ return -EINVAL;
+
+ /* Note: APIC ID = 0xff is used for broadcast.
+ * APIC ID > 0xff is reserved.
+ */
+ h_phy_apic_id = __default_cpu_present_to_apicid(cpu);
+
+ if (h_phy_apic_id >= AVIC_PHY_APIC_ID_MAX)
+ return -EINVAL;
+
+ entry = svm->avic_phy_apic_id_cache;
+ if (!entry)
+ return -EINVAL;
+
+ if (is_load) {
+ new_entry = READ_ONCE(*entry);
+
+ BUG_ON(new_entry & AVIC_PHY_APIC_ID__IS_RUN_MSK);
+
+ new_entry &= ~AVIC_PHY_APIC_ID__HOST_PHY_APIC_ID_MSK;
+ new_entry |= (h_phy_apic_id & AVIC_PHY_APIC_ID__HOST_PHY_APIC_ID_MSK);
+
+ /**
+ * Restore AVIC running flag if it was set during
+ * vcpu unload.
+ */
+ if (svm->avic_was_running)
+ new_entry |= AVIC_PHY_APIC_ID__IS_RUN_MSK;
+ else
+ new_entry &= ~AVIC_PHY_APIC_ID__IS_RUN_MSK;
+
+ WRITE_ONCE(*entry, new_entry);
+
+ } else {
+ new_entry = READ_ONCE(*entry);
+
+ /**
+ * This handles the case when vcpu is scheduled out
+ * and has not yet not called blocking. We save the
+ * AVIC running flag so that we can restore later.
+ */
+ if (new_entry & AVIC_PHY_APIC_ID__IS_RUN_MSK) {
+ svm->avic_was_running = true;
+ new_entry &= ~AVIC_PHY_APIC_ID__IS_RUN_MSK;
+ WRITE_ONCE(*entry, new_entry);
+ } else {
+ svm->avic_was_running = false;
+ }
+ }
+
+ return ret;
+}
+
+/**
+ * This function is called during VCPU halt/unhalt.
+ */
+static int avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
+{
+ int ret = 0;
+ int h_phy_apic_id;
+ u64 *entry, new_entry;
+ struct vcpu_svm *svm = to_svm(vcpu);
+
+ if (!svm_vcpu_avic_enabled(svm))
+ return 0;
+
+ /* Note: APIC ID = 0xff is used for broadcast.
+ * APIC ID > 0xff is reserved.
+ */
+ h_phy_apic_id = __default_cpu_present_to_apicid(vcpu->cpu);
+
+ if (h_phy_apic_id >= AVIC_PHY_APIC_ID_MAX)
+ return -EINVAL;
+
+ entry = svm->avic_phy_apic_id_cache;
+ if (!entry)
+ return -EINVAL;
+
+ if (is_run) {
+ /* Handle vcpu unblocking after HLT */
+ new_entry = READ_ONCE(*entry);
+ new_entry |= AVIC_PHY_APIC_ID__IS_RUN_MSK;
+ WRITE_ONCE(*entry, new_entry);
+ } else {
+ /* Handle vcpu blocking due to HLT */
+ new_entry = READ_ONCE(*entry);
+ new_entry &= ~AVIC_PHY_APIC_ID__IS_RUN_MSK;
+ WRITE_ONCE(*entry, new_entry);
+ }
+
+ return ret;
+}
+
static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
{
struct vcpu_svm *svm = to_svm(vcpu);
@@ -1476,6 +1581,8 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
/* This assumes that the kernel never uses MSR_TSC_AUX */
if (static_cpu_has(X86_FEATURE_RDTSCP))
wrmsrl(MSR_TSC_AUX, svm->tsc_aux);
+
+ avic_vcpu_load(vcpu, cpu, true);
}

static void svm_vcpu_put(struct kvm_vcpu *vcpu)
@@ -1483,6 +1590,8 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
struct vcpu_svm *svm = to_svm(vcpu);
int i;

+ avic_vcpu_load(vcpu, 0, false);
+
++vcpu->stat.host_state_reload;
kvm_load_ldt(svm->host.ldt);
#ifdef CONFIG_X86_64
@@ -1498,6 +1607,16 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
}

+static void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
+{
+ avic_set_running(vcpu, false);
+}
+
+static void svm_vcpu_unblocking(struct kvm_vcpu *vcpu)
+{
+ avic_set_running(vcpu, true);
+}
+
static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
{
return to_svm(vcpu)->vmcb->save.rflags;
@@ -4876,6 +4995,8 @@ static struct kvm_x86_ops svm_x86_ops = {
.prepare_guest_switch = svm_prepare_guest_switch,
.vcpu_load = svm_vcpu_load,
.vcpu_put = svm_vcpu_put,
+ .vcpu_blocking = svm_vcpu_blocking,
+ .vcpu_unblocking = svm_vcpu_unblocking,

.update_bp_intercept = update_bp_intercept,
.get_msr = svm_get_msr,
--
1.9.1