[2/5] KVM: SVM: Optimize nested svm msrpm merging

Commit Message

Joerg Roedel Feb. 25, 2010, 5:15 p.m. UTC

None

Patch

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d8d4e35..d15e0ea 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -92,6 +92,9 @@  struct nested_state {
 
 };
 
+#define MSRPM_OFFSETS	16
+static u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
+
 struct vcpu_svm {
 	struct kvm_vcpu vcpu;
 	struct vmcb *vmcb;
@@ -436,6 +439,34 @@  err_1:
 
 }
 
+static void add_msr_offset(u32 offset)
+{
+	u32 old;
+	int i;
+
+again:
+	for (i = 0; i < MSRPM_OFFSETS; ++i) {
+		old = msrpm_offsets[i];
+
+		if (old == offset)
+			return;
+
+		if (old != MSR_INVALID)
+			continue;
+
+		if (cmpxchg(&msrpm_offsets[i], old, offset) != old)
+			goto again;
+
+		return;
+	}
+
+	/*
+	 * If this BUG triggers the msrpm_offsets table has an overflow. Just
+	 * increase MSRPM_OFFSETS in this case.
+	 */
+	BUG();
+}
+
 static void set_msr_interception(u32 *msrpm, unsigned msr,
 				 int read, int write)
 {
@@ -454,6 +485,8 @@  static void set_msr_interception(u32 *msrpm, unsigned msr,
 	read  ? clear_bit(bit_read,  &tmp) : set_bit(bit_read,  &tmp);
 	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
 
+	add_msr_offset(offset);
+
 	msrpm[offset] = tmp;
 }
 
@@ -511,6 +544,8 @@  static __init int svm_hardware_setup(void)
 	memset(iopm_va, 0xff, PAGE_SIZE * (1 << IOPM_ALLOC_ORDER));
 	iopm_base = page_to_pfn(iopm_pages) << PAGE_SHIFT;
 
+	memset(msrpm_offsets, 0xff, sizeof(msrpm_offsets));
+
 	if (boot_cpu_has(X86_FEATURE_NX))
 		kvm_enable_efer_bits(EFER_NX);
 
@@ -775,6 +810,7 @@  static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
 	svm->nested.hsave = page_address(hsave_page);
 
 	svm->nested.msrpm = page_address(nested_msrpm_pages);
+	svm_vcpu_init_msrpm(svm->nested.msrpm);
 
 	svm->vmcb = page_address(page);
 	clear_page(svm->vmcb);
@@ -1846,20 +1882,33 @@  static int nested_svm_vmexit(struct vcpu_svm *svm)
 
 static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
 {
-	u32 *nested_msrpm;
-	struct page *page;
+	/*
+	 * This function merges the msr permission bitmaps of kvm and the
+	 * nested vmcb. It is omptimized in that it only merges the parts where
+	 * the kvm msr permission bitmap may contain zero bits
+	 */
 	int i;
 
-	nested_msrpm = nested_svm_map(svm, svm->nested.vmcb_msrpm, &page);
-	if (!nested_msrpm)
-		return false;
+	if (!(svm->nested.intercept & (1ULL << INTERCEPT_MSR_PROT)))
+		return true;
 
-	for (i = 0; i < PAGE_SIZE * (1 << MSRPM_ALLOC_ORDER) / 4; i++)
-		svm->nested.msrpm[i] = svm->msrpm[i] | nested_msrpm[i];
+	for (i = 0; i < MSRPM_OFFSETS; i++) {
+		u32 value, p;
+		u64 offset;
 
-	svm->vmcb->control.msrpm_base_pa = __pa(svm->nested.msrpm);
+		if (msrpm_offsets[i] == 0xffffffff)
+			break;
 
-	nested_svm_unmap(page);
+		p      = msrpm_offsets[i];
+		offset = svm->nested.vmcb_msrpm + (p * 4);
+
+		if (kvm_read_guest(svm->vcpu.kvm, offset, &value, 4))
+			return false;
+
+		svm->nested.msrpm[p] = svm->msrpm[p] | value;
+	}
+
+	svm->vmcb->control.msrpm_base_pa = __pa(svm->nested.msrpm);
 
 	return true;
 }