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

Punit Agrawal
2016-09-06T15:45:54Z

Christoffer Dall <christoffer.dall@linaro.org> writes:

> On Mon, Sep 05, 2016 at 05:31:36PM +0100, Punit Agrawal wrote:
>> 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);
>
> why do we need to clear TGE for the TLB maintenance instructions to
> work?
>
> Perhaps this is worth explaining in a comment.

I've added the following comment before clearing TGE bit.

"When VHE is enabled and HCR_EL2.TGE=1, EL1&0 TLB operations
apply to EL2&0 translation regime. As we prepare to emulate
guest TLB operation clear HCR_TGE to target TLB operations
to EL1&0 (guest)."

>
> Otherwise this looks ok to me.

Thanks for taking a look.

Punit

>
> -Christoffer
>
>> +}
>> +
>> +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
>>
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