KVM: vmx: shadow more fields that are read/written on every vmexits

Web:        https://git.kernel.org/torvalds/c/c5d167b27e00026711ad19a33a23d5d3d562148a
Commit:     c5d167b27e00026711ad19a33a23d5d3d562148a
Parent:     7cd918047a8bcb29501e6130e0e7eca98c78fe4d
Refname:    refs/heads/master
Author:     Paolo Bonzini <[email protected]>
AuthorDate: Wed Dec 13 11:05:19 2017 +0100
Committer:  Radim Krčmář <[email protected]>
CommitDate: Tue Jan 16 16:49:44 2018 +0100

    KVM: vmx: shadow more fields that are read/written on every vmexits
    
    Compared to when VMCS shadowing was added to KVM, we are reading/writing
    a few more fields: the PML index, the interrupt status and the preemption
    timer value.  The first two are because we are exposing more features
    to nested guests, the preemption timer is simply because we have grown
    a new optimization.  Adding them to the shadow VMCS field lists reduces
    the cost of a vmexit by about 1000 clock cycles for each field that exists
    on bare metal.
    
    On the other hand, the guest BNDCFGS and TSC offset are not written on
    fast paths, so remove them.
    
    Suggested-by: Jim Mattson <[email protected]>
    Cc: Jim Mattson <[email protected]>
    Cc: Wanpeng Li <[email protected]>
    Signed-off-by: Paolo Bonzini <[email protected]>
    Signed-off-by: Radim Krčmář <[email protected]>
---
 arch/x86/kvm/vmx.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2c8749ee3221..7b114a293c66 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -726,11 +726,12 @@ static unsigned long shadow_read_write_fields[] = {
 	GUEST_CS_LIMIT,
 	GUEST_CS_BASE,
 	GUEST_ES_BASE,
-	GUEST_BNDCFGS,
+	GUEST_PML_INDEX,
+	GUEST_INTR_STATUS,
+	VMX_PREEMPTION_TIMER_VALUE,
 	CR0_GUEST_HOST_MASK,
 	CR0_READ_SHADOW,
 	CR4_READ_SHADOW,
-	TSC_OFFSET,
 	EXCEPTION_BITMAP,
 	CPU_BASED_VM_EXEC_CONTROL,
 	VM_ENTRY_EXCEPTION_ERROR_CODE,
@@ -3903,9 +3904,22 @@ static void init_vmcs_shadow_fields(void)
 	/* No checks for read only fields yet */
 
 	for (i = j = 0; i < max_shadow_read_write_fields; i++) {
+		/*
+		 * PML and the preemption timer can be emulated, but the
+		 * processor cannot vmwrite to fields that don't exist
+		 * on bare metal.
+		 */
 		switch (shadow_read_write_fields[i]) {
-		case GUEST_BNDCFGS:
-			if (!kvm_mpx_supported())
+		case GUEST_PML_INDEX:
+			if (!cpu_has_vmx_pml())
+				continue;
+			break;
+		case VMX_PREEMPTION_TIMER_VALUE:
+			if (!cpu_has_vmx_preemption_timer())
+				continue;
+			break;
+		case GUEST_INTR_STATUS:
+			if (!cpu_has_vmx_apicv())
 				continue;
 			break;
 		default:
@@ -6802,11 +6816,6 @@ static __init int hardware_setup(void)
 		!(cpu_has_vmx_invvpid_single() || cpu_has_vmx_invvpid_global()))
 		enable_vpid = 0;
 
-	if (!cpu_has_vmx_shadow_vmcs())
-		enable_shadow_vmcs = 0;
-	if (enable_shadow_vmcs)
-		init_vmcs_shadow_fields();