From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 6 Nov 2017 13:31:12 +0100
Subject: kvm: vmx: Reinstate support for CPUs without virtual NMI
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Patch-mainline: v4.15-rc1
Git-commit: 8a1b43922d0d1279e7936ba85c4c2a870403c95f
References: bsc#1077761
This is more or less a revert of commit 2c82878b0cb3 ("KVM: VMX: require
virtual NMI support", 2017-03-27); it turns out that Core 2 Duo machines
only had virtual NMIs in some SKUs.
The revert is not trivial because in the meanwhile there have been several
fixes to nested NMI injection. Therefore, the entire vNMI state is moved
to struct loaded_vmcs.
Another change compared to before the patch is a simplification here:
if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked &&
!(is_guest_mode(vcpu) && nested_cpu_has_virtual_nmis(
get_vmcs12(vcpu))))) {
The final condition here is always true (because nested_cpu_has_virtual_nmis
is always false) and is removed.
Fixes: 2c82878b0cb38fd516fd612c67852a6bbf282003
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1490803
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
---
arch/x86/kvm/vmx.c | 150 +++++++++++++++++++++++++++++++++++++----------------
1 file changed, 106 insertions(+), 44 deletions(-)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -198,6 +198,10 @@
int cpu;
bool launched;
bool nmi_known_unmasked;
+ /* Support for vnmi-less CPUs */
+ int soft_vnmi_blocked;
+ ktime_t entry_time;
+ s64 vnmi_blocked_time;
struct list_head loaded_vmcss_on_cpu_link;
};
@@ -1288,6 +1292,11 @@
SECONDARY_EXEC_ENABLE_INVPCID;
}
+static inline bool cpu_has_virtual_nmis(void)
+{
+ return vmcs_config.pin_based_exec_ctrl & PIN_BASED_VIRTUAL_NMIS;
+}
+
static inline bool cpu_has_vmx_wbinvd_exit(void)
{
return vmcs_config.cpu_based_2nd_exec_ctrl &
@@ -1345,11 +1354,6 @@
(vmcs12->secondary_vm_exec_control & bit);
}
-static inline bool nested_cpu_has_virtual_nmis(struct vmcs12 *vmcs12)
-{
- return vmcs12->pin_based_vm_exec_control & PIN_BASED_VIRTUAL_NMIS;
-}
-
static inline bool nested_cpu_has_preemption_timer(struct vmcs12 *vmcs12)
{
return vmcs12->pin_based_vm_exec_control &
@@ -3709,9 +3713,9 @@
&_vmexit_control) < 0)
return -EIO;
- min = PIN_BASED_EXT_INTR_MASK | PIN_BASED_NMI_EXITING |
- PIN_BASED_VIRTUAL_NMIS;
- opt = PIN_BASED_POSTED_INTR | PIN_BASED_VMX_PREEMPTION_TIMER;
+ min = PIN_BASED_EXT_INTR_MASK | PIN_BASED_NMI_EXITING;
+ opt = PIN_BASED_VIRTUAL_NMIS | PIN_BASED_POSTED_INTR |
+ PIN_BASED_VMX_PREEMPTION_TIMER;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_PINBASED_CTLS,
&_pin_based_exec_control) < 0)
return -EIO;
@@ -5656,7 +5660,8 @@
static void enable_nmi_window(struct kvm_vcpu *vcpu)
{
- if (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_STI) {
+ if (!cpu_has_virtual_nmis() ||
+ vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_STI) {
enable_irq_window(vcpu);
return;
}
@@ -5696,6 +5701,19 @@
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ if (!cpu_has_virtual_nmis()) {
+ /*
+ * Tracking the NMI-blocked state in software is built upon
+ * finding the next open IRQ window. This, in turn, depends on
+ * well-behaving guests: They have to keep IRQs disabled at
+ * least as long as the NMI handler runs. Otherwise we may
+ * cause NMI nesting, maybe breaking the guest. But as this is
+ * highly unlikely, we can live with the residual risk.
+ */
+ vmx->loaded_vmcs->soft_vnmi_blocked = 1;
+ vmx->loaded_vmcs->vnmi_blocked_time = 0;
+ }
+
++vcpu->stat.nmi_injections;
vmx->loaded_vmcs->nmi_known_unmasked = false;
@@ -5714,6 +5732,8 @@
struct vcpu_vmx *vmx = to_vmx(vcpu);
bool masked;
+ if (!cpu_has_virtual_nmis())
+ return vmx->loaded_vmcs->soft_vnmi_blocked;
if (vmx->loaded_vmcs->nmi_known_unmasked)
return false;
masked = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_NMI;
@@ -5725,13 +5745,20 @@
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- vmx->loaded_vmcs->nmi_known_unmasked = !masked;
- if (masked)
- vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
- GUEST_INTR_STATE_NMI);
- else
- vmcs_clear_bits(GUEST_INTERRUPTIBILITY_INFO,
- GUEST_INTR_STATE_NMI);
+ if (!cpu_has_virtual_nmis()) {
+ if (vmx->loaded_vmcs->soft_vnmi_blocked != masked) {
+ vmx->loaded_vmcs->soft_vnmi_blocked = masked;
+ vmx->loaded_vmcs->vnmi_blocked_time = 0;
+ }
+ } else {
+ vmx->loaded_vmcs->nmi_known_unmasked = !masked;
+ if (masked)
+ vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
+ GUEST_INTR_STATE_NMI);
+ else
+ vmcs_clear_bits(GUEST_INTERRUPTIBILITY_INFO,
+ GUEST_INTR_STATE_NMI);
+ }
}
static int vmx_nmi_allowed(struct kvm_vcpu *vcpu)
@@ -5739,6 +5766,10 @@
if (to_vmx(vcpu)->nested.nested_run_pending)
return 0;
+ if (!cpu_has_virtual_nmis() &&
+ to_vmx(vcpu)->loaded_vmcs->soft_vnmi_blocked)
+ return 0;
+
return !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) &
(GUEST_INTR_STATE_MOV_SS | GUEST_INTR_STATE_STI
| GUEST_INTR_STATE_NMI));
@@ -6466,6 +6497,7 @@
* AAK134, BY25.
*/
if (!(to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+ cpu_has_virtual_nmis() &&
(exit_qualification & INTR_INFO_UNBLOCK_NMI))
vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO, GUEST_INTR_STATE_NMI);
@@ -6952,7 +6984,7 @@
}
/* Create a new VMCS */
- item = kmalloc(sizeof(struct vmcs02_list), GFP_KERNEL);
+ item = kzalloc(sizeof(struct vmcs02_list), GFP_KERNEL);
if (!item)
return NULL;
item->vmcs02.vmcs = alloc_vmcs();
@@ -7969,6 +8001,7 @@
* "blocked by NMI" bit has to be set before next VM entry.
*/
if (!(to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+ cpu_has_virtual_nmis() &&
(exit_qualification & INTR_INFO_UNBLOCK_NMI))
vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
GUEST_INTR_STATE_NMI);
@@ -8813,6 +8846,25 @@
return 0;
}
+ if (unlikely(!cpu_has_virtual_nmis() &&
+ vmx->loaded_vmcs->soft_vnmi_blocked)) {
+ if (vmx_interrupt_allowed(vcpu)) {
+ vmx->loaded_vmcs->soft_vnmi_blocked = 0;
+ } else if (vmx->loaded_vmcs->vnmi_blocked_time > 1000000000LL &&
+ vcpu->arch.nmi_pending) {
+ /*
+ * This CPU don't support us in finding the end of an
+ * NMI-blocked window if the guest runs with IRQs
+ * disabled. So we pull the trigger after 1 s of
+ * futile waiting, but inform the user about this.
+ */
+ printk(KERN_WARNING "%s: Breaking out of NMI-blocked "
+ "state on VCPU %d after 1 s timeout\n",
+ __func__, vcpu->vcpu_id);
+ vmx->loaded_vmcs->soft_vnmi_blocked = 0;
+ }
+ }
+
if (exit_reason < kvm_vmx_max_exit_handlers
&& kvm_vmx_exit_handlers[exit_reason])
return kvm_vmx_exit_handlers[exit_reason](vcpu);
@@ -9095,33 +9147,38 @@
idtv_info_valid = vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK;
- if (vmx->loaded_vmcs->nmi_known_unmasked)
- return;
- /*
- * Can't use vmx->exit_intr_info since we're not sure what
- * the exit reason is.
- */
- exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
- unblock_nmi = (exit_intr_info & INTR_INFO_UNBLOCK_NMI) != 0;
- vector = exit_intr_info & INTR_INFO_VECTOR_MASK;
- /*
- * SDM 3: 27.7.1.2 (September 2008)
- * Re-set bit "block by NMI" before VM entry if vmexit caused by
- * a guest IRET fault.
- * SDM 3: 23.2.2 (September 2008)
- * Bit 12 is undefined in any of the following cases:
- * If the VM exit sets the valid bit in the IDT-vectoring
- * information field.
- * If the VM exit is due to a double fault.
- */
- if ((exit_intr_info & INTR_INFO_VALID_MASK) && unblock_nmi &&
- vector != DF_VECTOR && !idtv_info_valid)
- vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
- GUEST_INTR_STATE_NMI);
- else
- vmx->loaded_vmcs->nmi_known_unmasked =
- !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO)
- & GUEST_INTR_STATE_NMI);
+ if (cpu_has_virtual_nmis()) {
+ if (vmx->loaded_vmcs->nmi_known_unmasked)
+ return;
+ /*
+ * Can't use vmx->exit_intr_info since we're not sure what
+ * the exit reason is.
+ */
+ exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+ unblock_nmi = (exit_intr_info & INTR_INFO_UNBLOCK_NMI) != 0;
+ vector = exit_intr_info & INTR_INFO_VECTOR_MASK;
+ /*
+ * SDM 3: 27.7.1.2 (September 2008)
+ * Re-set bit "block by NMI" before VM entry if vmexit caused by
+ * a guest IRET fault.
+ * SDM 3: 23.2.2 (September 2008)
+ * Bit 12 is undefined in any of the following cases:
+ * If the VM exit sets the valid bit in the IDT-vectoring
+ * information field.
+ * If the VM exit is due to a double fault.
+ */
+ if ((exit_intr_info & INTR_INFO_VALID_MASK) && unblock_nmi &&
+ vector != DF_VECTOR && !idtv_info_valid)
+ vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
+ GUEST_INTR_STATE_NMI);
+ else
+ vmx->loaded_vmcs->nmi_known_unmasked =
+ !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO)
+ & GUEST_INTR_STATE_NMI);
+ } else if (unlikely(vmx->loaded_vmcs->soft_vnmi_blocked))
+ vmx->loaded_vmcs->vnmi_blocked_time +=
+ ktime_to_ns(ktime_sub(ktime_get(),
+ vmx->loaded_vmcs->entry_time));
}
static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu,
@@ -9238,6 +9295,11 @@
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long debugctlmsr, cr4;
+ /* Record the guest's net vcpu time for enforced NMI injections. */
+ if (unlikely(!cpu_has_virtual_nmis() &&
+ vmx->loaded_vmcs->soft_vnmi_blocked))
+ vmx->loaded_vmcs->entry_time = ktime_get();
+
/* Don't enter VMX if guest state is invalid, let the exit handler
start emulation until we arrive back to a valid state */
if (vmx->emulation_required)