arm64: KVM: Add support for 16-bit VMID

The ARMv8.1 architecture extension allows to choose between 8-bit and
16-bit of VMID, so use this capability for KVM.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/include/asm/kvm_arm.h

@@ -164,7 +164,7 @@
 #define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
 #define VTTBR_BADDR_MASK  (((_AC(1, ULL) << (40 - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
 #define VTTBR_VMID_SHIFT  _AC(48, ULL)
-#define VTTBR_VMID_MASK	  (_AC(0xff, ULL) << VTTBR_VMID_SHIFT)
+#define VTTBR_VMID_MASK(size)	(_AT(u64, (1 << size) - 1) << VTTBR_VMID_SHIFT)
 
 /* Hyp Syndrome Register (HSR) bits */
 #define HSR_EC_SHIFT	(26)

arch/arm/include/asm/kvm_mmu.h

@@ -279,6 +279,11 @@ static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd,
 				       pgd_t *merged_hyp_pgd,
 				       unsigned long hyp_idmap_start) { }
 
+static inline unsigned int kvm_get_vmid_bits(void)
+{
+	return 8;
+}
+
 #endif	/* !__ASSEMBLY__ */
 
 #endif /* __ARM_KVM_MMU_H__ */

arch/arm/kvm/arm.c

@@ -59,7 +59,8 @@ static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_arm_running_vcpu);
 
 /* The VMID used in the VTTBR */
 static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
-static u8 kvm_next_vmid;
+static u32 kvm_next_vmid;
+static unsigned int kvm_vmid_bits __read_mostly;
 static DEFINE_SPINLOCK(kvm_vmid_lock);
 
 static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
@@ -434,11 +435,12 @@ static void update_vttbr(struct kvm *kvm)
 	kvm->arch.vmid_gen = atomic64_read(&kvm_vmid_gen);
 	kvm->arch.vmid = kvm_next_vmid;
 	kvm_next_vmid++;
+	kvm_next_vmid &= (1 << kvm_vmid_bits) - 1;
 
 	/* update vttbr to be used with the new vmid */
 	pgd_phys = virt_to_phys(kvm_get_hwpgd(kvm));
 	BUG_ON(pgd_phys & ~VTTBR_BADDR_MASK);
-	vmid = ((u64)(kvm->arch.vmid) << VTTBR_VMID_SHIFT) & VTTBR_VMID_MASK;
+	vmid = ((u64)(kvm->arch.vmid) << VTTBR_VMID_SHIFT) & VTTBR_VMID_MASK(kvm_vmid_bits);
 	kvm->arch.vttbr = pgd_phys | vmid;
 
 	spin_unlock(&kvm_vmid_lock);
@@ -1135,6 +1137,10 @@ static int init_hyp_mode(void)
 
 	kvm_perf_init();
 
+	/* set size of VMID supported by CPU */
+	kvm_vmid_bits = kvm_get_vmid_bits();
+	kvm_info("%d-bit VMID\n", kvm_vmid_bits);
+
 	kvm_info("Hyp mode initialized successfully\n");
 
 	return 0;

arch/arm64/include/asm/kvm_arm.h

@@ -125,6 +125,7 @@
 #define VTCR_EL2_SL0_LVL1	(1 << 6)
 #define VTCR_EL2_T0SZ_MASK	0x3f
 #define VTCR_EL2_T0SZ_40B	24
+#define VTCR_EL2_VS		19
 
 /*
  * We configure the Stage-2 page tables to always restrict the IPA space to be
@@ -169,7 +170,7 @@
 #define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
 #define VTTBR_BADDR_MASK  (((UL(1) << (PHYS_MASK_SHIFT - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
 #define VTTBR_VMID_SHIFT  (UL(48))
-#define VTTBR_VMID_MASK	  (UL(0xFF) << VTTBR_VMID_SHIFT)
+#define VTTBR_VMID_MASK(size) (_AT(u64, (1 << size) - 1) << VTTBR_VMID_SHIFT)
 
 /* Hyp System Trap Register */
 #define HSTR_EL2_T(x)	(1 << x)

arch/arm64/include/asm/kvm_mmu.h

@@ -20,6 +20,7 @@
 
 #include <asm/page.h>
 #include <asm/memory.h>
+#include <asm/cpufeature.h>
 
 /*
  * As we only have the TTBR0_EL2 register, we cannot express
@@ -301,5 +302,12 @@ static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd,
 	merged_hyp_pgd[idmap_idx] = __pgd(__pa(boot_hyp_pgd) | PMD_TYPE_TABLE);
 }
 
+static inline unsigned int kvm_get_vmid_bits(void)
+{
+	int reg = read_system_reg(SYS_ID_AA64MMFR1_EL1);
+
+	return (cpuid_feature_extract_field(reg, ID_AA64MMFR1_VMIDBITS_SHIFT) == 2) ? 16 : 8;
+}
+
 #endif /* __ASSEMBLY__ */
 #endif /* __ARM64_KVM_MMU_H__ */

arch/arm64/kvm/hyp-init.S

@@ -94,6 +94,15 @@ __do_hyp_init:
 	 */
 	mrs	x5, ID_AA64MMFR0_EL1
 	bfi	x4, x5, #16, #3
+	/*
+	 * Read the VMIDBits bits from ID_AA64MMFR1_EL1 and set the VS bit in
+	 * VTCR_EL2.
+	 */
+	mrs	x5, ID_AA64MMFR1_EL1
+	ubfx	x5, x5, #5, #1
+	lsl	x5, x5, #VTCR_EL2_VS
+	orr	x4, x4, x5
+
 	msr	vtcr_el2, x4
 
 	mrs	x4, mair_el1