[RFC PATCH v2 21/38] KVM: arm64: Set a handler for the system instruction traps

Christoffer Dall
2017-07-30T20:00:15Z

On Tue, Jul 18, 2017 at 11:58:47AM -0500, Jintack Lim wrote:
> When HCR.NV bit is set, execution of the EL2 translation regime address
> aranslation instructions and TLB maintenance instructions are trapped to

translation

> EL2. In addition, execution of the EL1 translation regime address
> aranslation instructions and TLB maintenance instructions that are only

translation

> accessible from EL2 and above are trapped to EL2. In these cases,
> ESR_EL2.EC will be set to 0x18.
>
> Change the existing handler to handle those system instructions as well
> as MRS/MSR instructions. Emulation of each system instructions will be
> done in separate patches.
>
> Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
> ---
> arch/arm64/include/asm/kvm_coproc.h | 2 +-
> arch/arm64/kvm/handle_exit.c | 2 +-
> arch/arm64/kvm/sys_regs.c | 53 ++++++++++++++++++++++++++++++++-----
> arch/arm64/kvm/trace.h | 2 +-
> 4 files changed, 50 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_coproc.h b/arch/arm64/include/asm/kvm_coproc.h
> index 0b52377..1b3d21b 100644
> --- a/arch/arm64/include/asm/kvm_coproc.h
> +++ b/arch/arm64/include/asm/kvm_coproc.h
> @@ -43,7 +43,7 @@ void kvm_register_target_sys_reg_table(unsigned int target,
> int kvm_handle_cp14_64(struct kvm_vcpu *vcpu, struct kvm_run *run);
> int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run);
> int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run);
> -int kvm_handle_sys_reg(struct kvm_vcpu *vcpu, struct kvm_run *run);
> +int kvm_handle_sys(struct kvm_vcpu *vcpu, struct kvm_run *run);
>
> #define kvm_coproc_table_init kvm_sys_reg_table_init
> void kvm_sys_reg_table_init(void);
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 9259881..d19e253 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -174,7 +174,7 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
> [ESR_ELx_EC_SMC32] = handle_smc,
> [ESR_ELx_EC_HVC64] = handle_hvc,
> [ESR_ELx_EC_SMC64] = handle_smc,
> - [ESR_ELx_EC_SYS64] = kvm_handle_sys_reg,
> + [ESR_ELx_EC_SYS64] = kvm_handle_sys,
> [ESR_ELx_EC_ERET] = kvm_handle_eret,
> [ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort,
> [ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort,
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 7062645..dbf5022 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1808,6 +1808,40 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
> return 1;
> }
>
> +static int emulate_tlbi(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *params)
> +{
> + /* TODO: support tlbi instruction emulation*/
> + kvm_inject_undefined(vcpu);
> + return 1;
> +}
> +
> +static int emulate_at(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *params)
> +{
> + /* TODO: support address translation instruction emulation */
> + kvm_inject_undefined(vcpu);
> + return 1;
> +}
> +
> +static int emulate_sys_instr(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *params)
> +{
> + int ret = 0;
> +
> + /* TLB maintenance instructions*/
> + if (params->CRn == 0b1000)
> + ret = emulate_tlbi(vcpu, params);
> + /* Address Translation instructions */
> + else if (params->CRn == 0b0111 && params->CRm == 0b1000)
> + ret = emulate_at(vcpu, params);

there are some style issues here. I think it would be nicer to do:

if (x) {
/* Foo */
do_something();
} else if (y) {
/* Bar */
do_something_else();
}

can you remind me why we'd not see any other than these particular two
classes of instructions here?

> +
> + if (ret)
> + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
> +
> + return ret;
> +}
> +
> static void reset_sys_reg_descs(struct kvm_vcpu *vcpu,
> const struct sys_reg_desc *table, size_t num)
> {
> @@ -1819,18 +1853,19 @@ static void reset_sys_reg_descs(struct kvm_vcpu *vcpu,
> }
>
> /**
> - * kvm_handle_sys_reg -- handles a mrs/msr trap on a guest sys_reg access
> + * kvm_handle_sys-- handles a system instruction or mrs/msr instruction trap
> + on a guest execution
> * @vcpu: The VCPU pointer
> * @run: The kvm_run struct
> */
> -int kvm_handle_sys_reg(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +int kvm_handle_sys(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> struct sys_reg_params params;
> unsigned long esr = kvm_vcpu_get_hsr(vcpu);
> int Rt = kvm_vcpu_sys_get_rt(vcpu);
> int ret;
>
> - trace_kvm_handle_sys_reg(esr);
> + trace_kvm_handle_sys(esr);
>
> params.is_aarch32 = false;
> params.is_32bit = false;
> @@ -1842,10 +1877,16 @@ int kvm_handle_sys_reg(struct kvm_vcpu *vcpu, struct kvm_run *run)
> params.regval = vcpu_get_reg(vcpu, Rt);
> params.is_write = !(esr & 1);
>
> - ret = emulate_sys_reg(vcpu, &params);
> + if (params.Op0 == 1) {
> + /* System instructions */
> + ret = emulate_sys_instr(vcpu, &params);
> + } else {
> + /* MRS/MSR instructions */
> + ret = emulate_sys_reg(vcpu, &params);
> + if (!params.is_write)
> + vcpu_set_reg(vcpu, Rt, params.regval);
> + }
>
> - if (!params.is_write)
> - vcpu_set_reg(vcpu, Rt, params.regval);
> return ret;
> }
>
> diff --git a/arch/arm64/kvm/trace.h b/arch/arm64/kvm/trace.h
> index 5f40987..192708e 100644
> --- a/arch/arm64/kvm/trace.h
> +++ b/arch/arm64/kvm/trace.h
> @@ -134,7 +134,7 @@
> TP_printk("%s %s reg %d (0x%08llx)", __entry->fn, __entry->is_write?"write to":"read from", __entry->reg, __entry->write_value)
> );
>
> -TRACE_EVENT(kvm_handle_sys_reg,
> +TRACE_EVENT(kvm_handle_sys,
> TP_PROTO(unsigned long hsr),
> TP_ARGS(hsr),
>
> --
> 1.9.1
>

Thanks,
-Christoffer