KVM: MIPS/VZ: Support guest hardware page table walker

Add support for VZ guest CP0_PWBase, CP0_PWField, CP0_PWSize, and
CP0_PWCtl registers for controlling the guest hardware page table walker
(HTW) present on P5600 and P6600 cores. These guest registers need
initialising on R6, context switching, and exposing via the KVM ioctl
API when they are present.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: linux-doc@vger.kernel.org

Documentation/virtual/kvm/api.txt

@@ -2081,7 +2081,11 @@ registers, find a list below:
   MIPS  | KVM_REG_MIPS_CP0_SEGCTL0      | 64
   MIPS  | KVM_REG_MIPS_CP0_SEGCTL1      | 64
   MIPS  | KVM_REG_MIPS_CP0_SEGCTL2      | 64
+  MIPS  | KVM_REG_MIPS_CP0_PWBASE       | 64
+  MIPS  | KVM_REG_MIPS_CP0_PWFIELD      | 64
+  MIPS  | KVM_REG_MIPS_CP0_PWSIZE       | 64
   MIPS  | KVM_REG_MIPS_CP0_WIRED        | 32
+  MIPS  | KVM_REG_MIPS_CP0_PWCTL        | 32
   MIPS  | KVM_REG_MIPS_CP0_HWRENA       | 32
   MIPS  | KVM_REG_MIPS_CP0_BADVADDR     | 64
   MIPS  | KVM_REG_MIPS_CP0_BADINSTR     | 32

arch/mips/include/asm/kvm_host.h

@@ -42,7 +42,11 @@
 #define KVM_REG_MIPS_CP0_SEGCTL0	MIPS_CP0_64(5, 2)
 #define KVM_REG_MIPS_CP0_SEGCTL1	MIPS_CP0_64(5, 3)
 #define KVM_REG_MIPS_CP0_SEGCTL2	MIPS_CP0_64(5, 4)
+#define KVM_REG_MIPS_CP0_PWBASE		MIPS_CP0_64(5, 5)
+#define KVM_REG_MIPS_CP0_PWFIELD	MIPS_CP0_64(5, 6)
+#define KVM_REG_MIPS_CP0_PWSIZE		MIPS_CP0_64(5, 7)
 #define KVM_REG_MIPS_CP0_WIRED		MIPS_CP0_32(6, 0)
+#define KVM_REG_MIPS_CP0_PWCTL		MIPS_CP0_32(6, 6)
 #define KVM_REG_MIPS_CP0_HWRENA		MIPS_CP0_32(7, 0)
 #define KVM_REG_MIPS_CP0_BADVADDR	MIPS_CP0_64(8, 0)
 #define KVM_REG_MIPS_CP0_BADINSTR	MIPS_CP0_32(8, 1)
@@ -678,7 +682,11 @@ __BUILD_KVM_RW_HW(pagegrain,      32, MIPS_CP0_TLB_PG_MASK,  1)
 __BUILD_KVM_RW_HW(segctl0,        l,  MIPS_CP0_TLB_PG_MASK,  2)
 __BUILD_KVM_RW_HW(segctl1,        l,  MIPS_CP0_TLB_PG_MASK,  3)
 __BUILD_KVM_RW_HW(segctl2,        l,  MIPS_CP0_TLB_PG_MASK,  4)
+__BUILD_KVM_RW_HW(pwbase,         l,  MIPS_CP0_TLB_PG_MASK,  5)
+__BUILD_KVM_RW_HW(pwfield,        l,  MIPS_CP0_TLB_PG_MASK,  6)
+__BUILD_KVM_RW_HW(pwsize,         l,  MIPS_CP0_TLB_PG_MASK,  7)
 __BUILD_KVM_RW_HW(wired,          32, MIPS_CP0_TLB_WIRED,    0)
+__BUILD_KVM_RW_HW(pwctl,          32, MIPS_CP0_TLB_WIRED,    6)
 __BUILD_KVM_RW_HW(hwrena,         32, MIPS_CP0_HWRENA,       0)
 __BUILD_KVM_RW_HW(badvaddr,       l,  MIPS_CP0_BAD_VADDR,    0)
 __BUILD_KVM_RW_HW(badinstr,       32, MIPS_CP0_BAD_VADDR,    1)

arch/mips/kvm/vz.c

@@ -1392,6 +1392,13 @@ static u64 kvm_vz_get_one_regs_segments[] = {
 	KVM_REG_MIPS_CP0_SEGCTL2,
 };
 
+static u64 kvm_vz_get_one_regs_htw[] = {
+	KVM_REG_MIPS_CP0_PWBASE,
+	KVM_REG_MIPS_CP0_PWFIELD,
+	KVM_REG_MIPS_CP0_PWSIZE,
+	KVM_REG_MIPS_CP0_PWCTL,
+};
+
 static u64 kvm_vz_get_one_regs_kscratch[] = {
 	KVM_REG_MIPS_CP0_KSCRATCH1,
 	KVM_REG_MIPS_CP0_KSCRATCH2,
@@ -1416,6 +1423,8 @@ static unsigned long kvm_vz_num_regs(struct kvm_vcpu *vcpu)
 		ret += ARRAY_SIZE(kvm_vz_get_one_regs_contextconfig);
 	if (cpu_guest_has_segments)
 		ret += ARRAY_SIZE(kvm_vz_get_one_regs_segments);
+	if (cpu_guest_has_htw)
+		ret += ARRAY_SIZE(kvm_vz_get_one_regs_htw);
 	ret += __arch_hweight8(cpu_data[0].guest.kscratch_mask);
 
 	return ret;
@@ -1461,6 +1470,12 @@ static int kvm_vz_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices)
 			return -EFAULT;
 		indices += ARRAY_SIZE(kvm_vz_get_one_regs_segments);
 	}
+	if (cpu_guest_has_htw) {
+		if (copy_to_user(indices, kvm_vz_get_one_regs_htw,
+				 sizeof(kvm_vz_get_one_regs_htw)))
+			return -EFAULT;
+		indices += ARRAY_SIZE(kvm_vz_get_one_regs_htw);
+	}
 	for (i = 0; i < 6; ++i) {
 		if (!cpu_guest_has_kscr(i + 2))
 			continue;
@@ -1564,9 +1579,29 @@ static int kvm_vz_get_one_reg(struct kvm_vcpu *vcpu,
 			return -EINVAL;
 		*v = read_gc0_segctl2();
 		break;
+	case KVM_REG_MIPS_CP0_PWBASE:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		*v = read_gc0_pwbase();
+		break;
+	case KVM_REG_MIPS_CP0_PWFIELD:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		*v = read_gc0_pwfield();
+		break;
+	case KVM_REG_MIPS_CP0_PWSIZE:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		*v = read_gc0_pwsize();
+		break;
 	case KVM_REG_MIPS_CP0_WIRED:
 		*v = (long)read_gc0_wired();
 		break;
+	case KVM_REG_MIPS_CP0_PWCTL:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		*v = read_gc0_pwctl();
+		break;
 	case KVM_REG_MIPS_CP0_HWRENA:
 		*v = (long)read_gc0_hwrena();
 		break;
@@ -1746,9 +1781,29 @@ static int kvm_vz_set_one_reg(struct kvm_vcpu *vcpu,
 			return -EINVAL;
 		write_gc0_segctl2(v);
 		break;
+	case KVM_REG_MIPS_CP0_PWBASE:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		write_gc0_pwbase(v);
+		break;
+	case KVM_REG_MIPS_CP0_PWFIELD:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		write_gc0_pwfield(v);
+		break;
+	case KVM_REG_MIPS_CP0_PWSIZE:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		write_gc0_pwsize(v);
+		break;
 	case KVM_REG_MIPS_CP0_WIRED:
 		change_gc0_wired(MIPSR6_WIRED_WIRED, v);
 		break;
+	case KVM_REG_MIPS_CP0_PWCTL:
+		if (!cpu_guest_has_htw)
+			return -EINVAL;
+		write_gc0_pwctl(v);
+		break;
 	case KVM_REG_MIPS_CP0_HWRENA:
 		write_gc0_hwrena(v);
 		break;
@@ -2179,6 +2234,14 @@ static int kvm_vz_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		kvm_restore_gc0_segctl2(cop0);
 	}
 
+	/* restore HTW registers */
+	if (cpu_guest_has_htw) {
+		kvm_restore_gc0_pwbase(cop0);
+		kvm_restore_gc0_pwfield(cop0);
+		kvm_restore_gc0_pwsize(cop0);
+		kvm_restore_gc0_pwctl(cop0);
+	}
+
 	/* restore Root.GuestCtl2 from unused Guest guestctl2 register */
 	if (cpu_has_guestctl2)
 		write_c0_guestctl2(
@@ -2268,6 +2331,15 @@ static int kvm_vz_vcpu_put(struct kvm_vcpu *vcpu, int cpu)
 		kvm_save_gc0_segctl2(cop0);
 	}
 
+	/* save HTW registers if enabled in guest */
+	if (cpu_guest_has_htw &&
+	    kvm_read_sw_gc0_config3(cop0) & MIPS_CONF3_PW) {
+		kvm_save_gc0_pwbase(cop0);
+		kvm_save_gc0_pwfield(cop0);
+		kvm_save_gc0_pwsize(cop0);
+		kvm_save_gc0_pwctl(cop0);
+	}
+
 	kvm_vz_save_timer(vcpu);
 
 	/* save Root.GuestCtl2 in unused Guest guestctl2 register */
@@ -2596,6 +2668,14 @@ static int kvm_vz_vcpu_setup(struct kvm_vcpu *vcpu)
 		kvm_write_sw_gc0_segctl2(cop0, 0x00380438);
 	}
 
+	/* reset HTW registers */
+	if (cpu_guest_has_htw && cpu_has_mips_r6) {
+		/* PWField */
+		kvm_write_sw_gc0_pwfield(cop0, 0x0c30c302);
+		/* PWSize */
+		kvm_write_sw_gc0_pwsize(cop0, 1 << MIPS_PWSIZE_PTW_SHIFT);
+	}
+
 	/* start with no pending virtual guest interrupts */
 	if (cpu_has_guestctl2)
 		cop0->reg[MIPS_CP0_GUESTCTL2][MIPS_CP0_GUESTCTL2_SEL] = 0;