KVM: nVMX: nested TPR shadow/threshold emulation
This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=61411
TPR shadow/threshold feature is important to speed up the Windows guest.
Besides, it is a must feature for certain VMM.
We map virtual APIC page address and TPR threshold from L1 VMCS. If
TPR_BELOW_THRESHOLD VM exit is triggered by L2 guest and L1 interested
in, we inject it into L1 VMM for handling.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
[Add PAGE_ALIGNED check, do not write useless virtual APIC page address
if TPR shadowing is disabled. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 70516e1..73ba2a2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -397,6 +397,7 @@
* we must keep them pinned while L2 runs.
*/
struct page *apic_access_page;
+ struct page *virtual_apic_page;
u64 msr_ia32_feature_control;
struct hrtimer preemption_timer;
@@ -555,6 +556,7 @@
ARRAY_SIZE(shadow_read_only_fields);
static unsigned long shadow_read_write_fields[] = {
+ TPR_THRESHOLD,
GUEST_RIP,
GUEST_RSP,
GUEST_CR0,
@@ -2352,7 +2354,7 @@
CPU_BASED_MOV_DR_EXITING | CPU_BASED_UNCOND_IO_EXITING |
CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_EXITING |
CPU_BASED_RDPMC_EXITING | CPU_BASED_RDTSC_EXITING |
- CPU_BASED_PAUSE_EXITING |
+ CPU_BASED_PAUSE_EXITING | CPU_BASED_TPR_SHADOW |
CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
/*
* We can allow some features even when not supported by the
@@ -6246,6 +6248,10 @@
nested_release_page(vmx->nested.apic_access_page);
vmx->nested.apic_access_page = 0;
}
+ if (vmx->nested.virtual_apic_page) {
+ nested_release_page(vmx->nested.virtual_apic_page);
+ vmx->nested.virtual_apic_page = 0;
+ }
nested_free_all_saved_vmcss(vmx);
}
@@ -7034,7 +7040,7 @@
case EXIT_REASON_MCE_DURING_VMENTRY:
return 0;
case EXIT_REASON_TPR_BELOW_THRESHOLD:
- return 1;
+ return nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW);
case EXIT_REASON_APIC_ACCESS:
return nested_cpu_has2(vmcs12,
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
@@ -7155,6 +7161,12 @@
static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
{
+ struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+
+ if (is_guest_mode(vcpu) &&
+ nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW))
+ return;
+
if (irr == -1 || tpr < irr) {
vmcs_write32(TPR_THRESHOLD, 0);
return;
@@ -7933,8 +7945,8 @@
struct vcpu_vmx *vmx = to_vmx(vcpu);
if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
+ /* TODO: Also verify bits beyond physical address width are 0 */
if (!PAGE_ALIGNED(vmcs12->apic_access_addr))
- /*TODO: Also verify bits beyond physical address width are 0*/
return false;
/*
@@ -7948,6 +7960,31 @@
vmx->nested.apic_access_page =
nested_get_page(vcpu, vmcs12->apic_access_addr);
}
+
+ if (nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW)) {
+ /* TODO: Also verify bits beyond physical address width are 0 */
+ if (!PAGE_ALIGNED(vmcs12->virtual_apic_page_addr))
+ return false;
+
+ if (vmx->nested.virtual_apic_page) /* shouldn't happen */
+ nested_release_page(vmx->nested.virtual_apic_page);
+ vmx->nested.virtual_apic_page =
+ nested_get_page(vcpu, vmcs12->virtual_apic_page_addr);
+
+ /*
+ * Failing the vm entry is _not_ what the processor does
+ * but it's basically the only possibility we have.
+ * We could still enter the guest if CR8 load exits are
+ * enabled, CR8 store exits are enabled, and virtualize APIC
+ * access is disabled; in this case the processor would never
+ * use the TPR shadow and we could simply clear the bit from
+ * the execution control. But such a configuration is useless,
+ * so let's keep the code simple.
+ */
+ if (!vmx->nested.virtual_apic_page)
+ return false;
+ }
+
return true;
}
@@ -8141,6 +8178,13 @@
exec_control &= ~CPU_BASED_VIRTUAL_NMI_PENDING;
exec_control &= ~CPU_BASED_TPR_SHADOW;
exec_control |= vmcs12->cpu_based_vm_exec_control;
+
+ if (exec_control & CPU_BASED_TPR_SHADOW) {
+ vmcs_write64(VIRTUAL_APIC_PAGE_ADDR,
+ page_to_phys(vmx->nested.virtual_apic_page));
+ vmcs_write32(TPR_THRESHOLD, vmcs12->tpr_threshold);
+ }
+
/*
* Merging of IO and MSR bitmaps not currently supported.
* Rather, exit every time.
@@ -8908,6 +8952,10 @@
nested_release_page(vmx->nested.apic_access_page);
vmx->nested.apic_access_page = 0;
}
+ if (vmx->nested.virtual_apic_page) {
+ nested_release_page(vmx->nested.virtual_apic_page);
+ vmx->nested.virtual_apic_page = 0;
+ }
/*
* Exiting from L2 to L1, we're now back to L1 which thinks it just