KVM: MTRR: introduce fixed_mtrr_segment table

This table summarizes the information of fixed MTRRs and introduce some APIs
to abstract its operation which helps us to clean up the code and will be
used in later patches

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
[Change range_size to range_shift, in order to avoid udivdi3 errors.
 - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mtrr.c

@@ -120,12 +120,132 @@ static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
 	return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
 }
 
+/*
+* Three terms are used in the following code:
+* - segment, it indicates the address segments covered by fixed MTRRs.
+* - unit, it corresponds to the MSR entry in the segment.
+* - range, a range is covered in one memory cache type.
+*/
+struct fixed_mtrr_segment {
+	u64 start;
+	u64 end;
+
+	int range_shift;
+
+	/* the start position in kvm_mtrr.fixed_ranges[]. */
+	int range_start;
+};
+
+static struct fixed_mtrr_segment fixed_seg_table[] = {
+	/* MSR_MTRRfix64K_00000, 1 unit. 64K fixed mtrr. */
+	{
+		.start = 0x0,
+		.end = 0x80000,
+		.range_shift = 16, /* 64K */
+		.range_start = 0,
+	},
+
+	/*
+	 * MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000, 2 units,
+	 * 16K fixed mtrr.
+	 */
+	{
+		.start = 0x80000,
+		.end = 0xc0000,
+		.range_shift = 14, /* 16K */
+		.range_start = 8,
+	},
+
+	/*
+	 * MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000, 8 units,
+	 * 4K fixed mtrr.
+	 */
+	{
+		.start = 0xc0000,
+		.end = 0x100000,
+		.range_shift = 12, /* 12K */
+		.range_start = 24,
+	}
+};
+
+/*
+ * The size of unit is covered in one MSR, one MSR entry contains
+ * 8 ranges so that unit size is always 8 * 2^range_shift.
+ */
+static u64 fixed_mtrr_seg_unit_size(int seg)
+{
+	return 8 << fixed_seg_table[seg].range_shift;
+}
+
+static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
+{
+	switch (msr) {
+	case MSR_MTRRfix64K_00000:
+		*seg = 0;
+		*unit = 0;
+		break;
+	case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
+		*seg = 1;
+		*unit = msr - MSR_MTRRfix16K_80000;
+		break;
+	case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
+		*seg = 2;
+		*unit = msr - MSR_MTRRfix4K_C0000;
+		break;
+	default:
+		return false;
+	}
+
+	return true;
+}
+
+static void fixed_mtrr_seg_unit_range(int seg, int unit, u64 *start, u64 *end)
+{
+	struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
+	u64 unit_size = fixed_mtrr_seg_unit_size(seg);
+
+	*start = mtrr_seg->start + unit * unit_size;
+	*end = *start + unit_size;
+	WARN_ON(*end > mtrr_seg->end);
+}
+
+static int fixed_mtrr_seg_unit_range_index(int seg, int unit)
+{
+	struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
+
+	WARN_ON(mtrr_seg->start + unit * fixed_mtrr_seg_unit_size(seg)
+		> mtrr_seg->end);
+
+	/* each unit has 8 ranges. */
+	return mtrr_seg->range_start + 8 * unit;
+}
+
+static bool fixed_msr_to_range(u32 msr, u64 *start, u64 *end)
+{
+	int seg, unit;
+
+	if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
+		return false;
+
+	fixed_mtrr_seg_unit_range(seg, unit, start, end);
+	return true;
+}
+
+static int fixed_msr_to_range_index(u32 msr)
+{
+	int seg, unit;
+
+	if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
+		return -1;
+
+	return fixed_mtrr_seg_unit_range_index(seg, unit);
+}
+
 static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 {
 	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 	gfn_t start, end, mask;
 	int index;
-	bool is_fixed = true;
 
 	if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
 	      !kvm_arch_has_noncoherent_dma(vcpu->kvm))
@@ -134,32 +254,15 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 	if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
 		return;
 
-	switch (msr) {
-	case MSR_MTRRfix64K_00000:
-		start = 0x0;
-		end = 0x80000;
-		break;
-	case MSR_MTRRfix16K_80000:
-		start = 0x80000;
-		end = 0xa0000;
-		break;
-	case MSR_MTRRfix16K_A0000:
-		start = 0xa0000;
-		end = 0xc0000;
-		break;
-	case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
-		index = msr - MSR_MTRRfix4K_C0000;
-		start = 0xc0000 + index * (32 << 10);
-		end = start + (32 << 10);
-		break;
-	case MSR_MTRRdefType:
-		is_fixed = false;
+	/* fixed MTRRs. */
+	if (fixed_msr_to_range(msr, &start, &end)) {
+		if (!fixed_mtrr_is_enabled(mtrr_state))
+			return;
+	} else if (msr == MSR_MTRRdefType) {
 		start = 0x0;
 		end = ~0ULL;
-		break;
-	default:
+	} else {
 		/* variable range MTRRs. */
-		is_fixed = false;
 		index = (msr - 0x200) / 2;
 		start = mtrr_state->var_ranges[index].base & PAGE_MASK;
 		mask = mtrr_state->var_ranges[index].mask & PAGE_MASK;
@@ -168,38 +271,32 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 		end = ((start & mask) | ~mask) + 1;
 	}
 
-	if (is_fixed && !fixed_mtrr_is_enabled(mtrr_state))
-		return;
-
 	kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
 }
 
 int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
-	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
+	int index;
 
 	if (!kvm_mtrr_valid(vcpu, msr, data))
 		return 1;
 
-	if (msr == MSR_MTRRdefType)
+	index = fixed_msr_to_range_index(msr);
+	if (index >= 0)
+		*(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index] = data;
+	else if (msr == MSR_MTRRdefType)
 		vcpu->arch.mtrr_state.deftype = data;
-	else if (msr == MSR_MTRRfix64K_00000)
-		p[0] = data;
-	else if (msr == MSR_MTRRfix16K_80000 || msr == MSR_MTRRfix16K_A0000)
-		p[1 + msr - MSR_MTRRfix16K_80000] = data;
-	else if (msr >= MSR_MTRRfix4K_C0000 && msr <= MSR_MTRRfix4K_F8000)
-		p[3 + msr - MSR_MTRRfix4K_C0000] = data;
 	else if (msr == MSR_IA32_CR_PAT)
 		vcpu->arch.pat = data;
 	else {	/* Variable MTRRs */
-		int idx, is_mtrr_mask;
+		int is_mtrr_mask;
 
-		idx = (msr - 0x200) / 2;
-		is_mtrr_mask = msr - 0x200 - 2 * idx;
+		index = (msr - 0x200) / 2;
+		is_mtrr_mask = msr - 0x200 - 2 * index;
 		if (!is_mtrr_mask)
-			vcpu->arch.mtrr_state.var_ranges[idx].base = data;
+			vcpu->arch.mtrr_state.var_ranges[index].base = data;
 		else
-			vcpu->arch.mtrr_state.var_ranges[idx].mask = data;
+			vcpu->arch.mtrr_state.var_ranges[index].mask = data;
 	}
 
 	update_mtrr(vcpu, msr);
@@ -208,7 +305,7 @@ int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 
 int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 {
-	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
+	int index;
 
 	/* MSR_MTRRcap is a readonly MSR. */
 	if (msr == MSR_MTRRcap) {
@@ -225,25 +322,22 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	if (!msr_mtrr_valid(msr))
 		return 1;
 
-	if (msr == MSR_MTRRdefType)
+	index = fixed_msr_to_range_index(msr);
+	if (index >= 0)
+		*pdata = *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index];
+	else if (msr == MSR_MTRRdefType)
 		*pdata = vcpu->arch.mtrr_state.deftype;
-	else if (msr == MSR_MTRRfix64K_00000)
-		*pdata = p[0];
-	else if (msr == MSR_MTRRfix16K_80000 || msr == MSR_MTRRfix16K_A0000)
-		*pdata = p[1 + msr - MSR_MTRRfix16K_80000];
-	else if (msr >= MSR_MTRRfix4K_C0000 && msr <= MSR_MTRRfix4K_F8000)
-		*pdata = p[3 + msr - MSR_MTRRfix4K_C0000];
 	else if (msr == MSR_IA32_CR_PAT)
 		*pdata = vcpu->arch.pat;
 	else {	/* Variable MTRRs */
-		int idx, is_mtrr_mask;
+		int is_mtrr_mask;
 
-		idx = (msr - 0x200) / 2;
-		is_mtrr_mask = msr - 0x200 - 2 * idx;
+		index = (msr - 0x200) / 2;
+		is_mtrr_mask = msr - 0x200 - 2 * index;
 		if (!is_mtrr_mask)
-			*pdata = vcpu->arch.mtrr_state.var_ranges[idx].base;
+			*pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
 		else
-			*pdata = vcpu->arch.mtrr_state.var_ranges[idx].mask;
+			*pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
 	}
 
 	return 0;