[RFC v2 PATCH 6/7] arm64: KVM: Handle trappable TLB instructions

Punit Agrawal
2016-09-05T16:33:25Z

The ARMv8 architecture allows trapping of TLB maintenane instructions
from EL0/EL1 to higher exception levels. On encountering a trappable TLB
instruction in a guest, an exception is taken to EL2.

Add functionality to handle emulating the TLB instructions.

Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/kvm_asm.h | 1 +
arch/arm64/kvm/hyp/tlb.c | 69 ++++++++++++++++++++++++++++++++++
arch/arm64/kvm/sys_regs.c | 81 ++++++++++++++++++++++++++++++++++++++++
arch/arm64/kvm/trace.h | 16 ++++++++
4 files changed, 167 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 7561f63..1ac1cc3 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -49,6 +49,7 @@ extern char __kvm_hyp_vector[];
extern void __kvm_flush_vm_context(void);
extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
+extern void __kvm_emulate_tlb_invalidate(struct kvm *kvm, u32 sysreg, u64 regval);

extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);

diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c
index 4cda100..1210f58 100644
--- a/arch/arm64/kvm/hyp/tlb.c
+++ b/arch/arm64/kvm/hyp/tlb.c
@@ -78,3 +78,72 @@ static void __hyp_text __tlb_flush_vm_context(void)
}

__alias(__tlb_flush_vm_context) void __kvm_flush_vm_context(void);
+
+/* Intentionally empty functions */
+static void __hyp_text __switch_to_hyp_role_nvhe(void) { }
+static void __hyp_text __switch_to_host_role_nvhe(void) { }
+
+static void __hyp_text __switch_to_hyp_role_vhe(void)
+{
+ u64 hcr = read_sysreg(hcr_el2);
+
+ hcr &= ~HCR_TGE;
+ write_sysreg(hcr, hcr_el2);
+}
+
+static void __hyp_text __switch_to_host_role_vhe(void)
+{
+ u64 hcr = read_sysreg(hcr_el2);
+
+ hcr |= HCR_TGE;
+ write_sysreg(hcr, hcr_el2);
+}
+
+static hyp_alternate_select(__switch_to_hyp_role,
+ __switch_to_hyp_role_nvhe,
+ __switch_to_hyp_role_vhe,
+ ARM64_HAS_VIRT_HOST_EXTN);
+
+static hyp_alternate_select(__switch_to_host_role,
+ __switch_to_host_role_nvhe,
+ __switch_to_host_role_vhe,
+ ARM64_HAS_VIRT_HOST_EXTN);
+
+static void __hyp_text __switch_to_guest_regime(struct kvm *kvm)
+{
+ write_sysreg(kvm->arch.vttbr, vttbr_el2);
+ __switch_to_hyp_role();
+ isb();
+}
+
+static void __hyp_text __switch_to_host_regime(void)
+{
+ __switch_to_host_role();
+ write_sysreg(0, vttbr_el2);
+}
+
+void __hyp_text
+__kvm_emulate_tlb_invalidate(struct kvm *kvm, u32 sys_op, u64 regval)
+{
+ kvm = kern_hyp_va(kvm);
+
+ /*
+ * Switch to the guest before performing any TLB operations to
+ * target the appropriate VMID
+ */
+ __switch_to_guest_regime(kvm);
+
+ /*
+ * TLB maintenance operations are broadcast to
+ * inner-shareable domain when HCR_FB is set (default for
+ * KVM).
+ *
+ * Nuke all Stage 1 TLB entries for the VM. This will kill
+ * performance but it's always safe to do as we don't leave
+ * behind any strays in the TLB
+ */
+ __tlbi(vmalle1is);
+ isb();
+
+ __switch_to_host_regime();
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e51367d..0e70da9 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -790,6 +790,18 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
return true;
}

+static bool emulate_tlb_invalidate(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
+ const struct sys_reg_desc *r)
+{
+ u32 opcode = sys_reg(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2);
+
+ kvm_call_hyp(__kvm_emulate_tlb_invalidate,
+ vcpu->kvm, opcode, p->regval);
+ trace_kvm_tlb_invalidate(*vcpu_pc(vcpu), opcode);
+
+ return true;
+}
+
/* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
#define DBG_BCR_BVR_WCR_WVR_EL1(n) \
/* DBGBVRn_EL1 */ \
@@ -841,6 +853,35 @@ static const struct sys_reg_desc sys_reg_descs[] = {
{ Op0(0b01), Op1(0b000), CRn(0b0111), CRm(0b1110), Op2(0b010),
access_dcsw },

+ /*
+ * ARMv8 ARM: Table C5-4 TLB maintenance instructions
+ * (Ref: ARMv8 ARM C5.1 version: ARM DDI 0487A.j)
+ */
+ /* TLBI VMALLE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(0), emulate_tlb_invalidate },
+ /* TLBI VAE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(1), emulate_tlb_invalidate },
+ /* TLBI ASIDE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(2), emulate_tlb_invalidate },
+ /* TLBI VAAE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(3), emulate_tlb_invalidate },
+ /* TLBI VALE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(5), emulate_tlb_invalidate },
+ /* TLBI VAALE1IS */
+ { Op0(1), Op1(0), CRn(8), CRm(3), Op2(7), emulate_tlb_invalidate },
+ /* TLBI VMALLE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(0), emulate_tlb_invalidate },
+ /* TLBI VAE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(1), emulate_tlb_invalidate },
+ /* TLBI ASIDE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(2), emulate_tlb_invalidate },
+ /* TLBI VAAE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(3), emulate_tlb_invalidate },
+ /* TLBI VALE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(5), emulate_tlb_invalidate },
+ /* TLBI VAALE1 */
+ { Op0(1), Op1(0), CRn(8), CRm(7), Op2(7), emulate_tlb_invalidate },
+
DBG_BCR_BVR_WCR_WVR_EL1(0),
DBG_BCR_BVR_WCR_WVR_EL1(1),
/* MDCCINT_EL1 */
@@ -1329,6 +1370,46 @@ static const struct sys_reg_desc cp15_regs[] = {
{ Op1( 0), CRn( 7), CRm(10), Op2( 2), access_dcsw },
{ Op1( 0), CRn( 7), CRm(14), Op2( 2), access_dcsw },

+ /*
+ * TLB operations
+ */
+ /* TLBIALLIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 0), emulate_tlb_invalidate},
+ /* TLBIMVAIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 1), emulate_tlb_invalidate},
+ /* TLBIASIDIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 2), emulate_tlb_invalidate},
+ /* TLBIMVAAIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 3), emulate_tlb_invalidate},
+ /* TLBIMVALIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 5), emulate_tlb_invalidate},
+ /* TLBIMVAALIS */
+ { Op1( 0), CRn( 8), CRm( 3), Op2( 7), emulate_tlb_invalidate},
+ /* ITLBIALL */
+ { Op1( 0), CRn( 8), CRm( 5), Op2( 0), emulate_tlb_invalidate},
+ /* ITLBIMVA */
+ { Op1( 0), CRn( 8), CRm( 5), Op2( 1), emulate_tlb_invalidate},
+ /* ITLBIASID */
+ { Op1( 0), CRn( 8), CRm( 5), Op2( 2), emulate_tlb_invalidate},
+ /* DTLBIALL */
+ { Op1( 0), CRn( 8), CRm( 6), Op2( 0), emulate_tlb_invalidate},
+ /* DTLBIMVA */
+ { Op1( 0), CRn( 8), CRm( 6), Op2( 1), emulate_tlb_invalidate},
+ /* DTLBIASID */
+ { Op1( 0), CRn( 8), CRm( 6), Op2( 2), emulate_tlb_invalidate},
+ /* TLBIALL */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 0), emulate_tlb_invalidate},
+ /* TLBIMVA */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 1), emulate_tlb_invalidate},
+ /* TLBIASID */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 2), emulate_tlb_invalidate},
+ /* TLBIMVAA */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 3), emulate_tlb_invalidate},
+ /* TLBIMVAL */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 5), emulate_tlb_invalidate},
+ /* TLBIMVAAL */
+ { Op1( 0), CRn( 8), CRm( 7), Op2( 7), emulate_tlb_invalidate},
+
/* PMU */
{ Op1( 0), CRn( 9), CRm(12), Op2( 0), access_pmcr },
{ Op1( 0), CRn( 9), CRm(12), Op2( 1), access_pmcnten },
diff --git a/arch/arm64/kvm/trace.h b/arch/arm64/kvm/trace.h
index 7fb0008..c4d577f 100644
--- a/arch/arm64/kvm/trace.h
+++ b/arch/arm64/kvm/trace.h
@@ -166,6 +166,22 @@ TRACE_EVENT(kvm_set_guest_debug,
TP_printk("vcpu: %p, flags: 0x%08x", __entry->vcpu, __entry->guest_debug)
);

+TRACE_EVENT(kvm_tlb_invalidate,
+ TP_PROTO(unsigned long vcpu_pc, u32 opcode),
+ TP_ARGS(vcpu_pc, opcode),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, vcpu_pc)
+ __field(u32, opcode)
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_pc = vcpu_pc;
+ __entry->opcode = opcode;
+ ),
+
+ TP_printk("vcpu_pc=0x%16lx opcode=%08x", __entry->vcpu_pc, __entry->opcode)
+);

#endif /* _TRACE_ARM64_KVM_H */

--
2.8.1