| Message ID | 20171123121134.11050-3-alex.bennee@linaro.org |
|---|---|
| State | Accepted |
| Commit | e3feebf81744acd8b581e5eb58a93e8fdcf042a5 |
| Headers | show |
| Series | [v1,1/2] kvm: arm64: handle single-step during SError exceptions | expand |
On Thu, Nov 23, 2017 at 12:11:34PM +0000, Alex Bennée wrote: > There is a fast-path of MMIO emulation inside hyp mode. The handling > of single-step is broadly the same as kvm_arm_handle_step_debug() > except we just setup ESR/HSR so handle_exit() does the correct thing > as we exit. > > For the case of an emulated illegal access causing an SError we will > exit via the ARM_EXCEPTION_EL1_SERROR path in handle_exit(). We behave > as we would during a real SError and clear the DBG_SPSR_SS bit for the > emulated instruction. > > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > --- > arch/arm64/kvm/hyp/switch.c | 37 ++++++++++++++++++++++++++++++------- > 1 file changed, 30 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > index 525c01f48867..f7c651f3a8c0 100644 > --- a/arch/arm64/kvm/hyp/switch.c > +++ b/arch/arm64/kvm/hyp/switch.c > @@ -22,6 +22,7 @@ > #include <asm/kvm_emulate.h> > #include <asm/kvm_hyp.h> > #include <asm/fpsimd.h> > +#include <asm/debug-monitors.h> > > static bool __hyp_text __fpsimd_enabled_nvhe(void) > { > @@ -269,7 +270,11 @@ static bool __hyp_text __populate_fault_info(struct kvm_vcpu *vcpu) > return true; > } > > -static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu) > +/* Skip an instruction which has been emulated. Returns true if > + * execution can continue or false if we need to exit hyp mode because > + * single-step was in effect. > + */ > +static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu) > { > *vcpu_pc(vcpu) = read_sysreg_el2(elr); > > @@ -282,6 +287,14 @@ static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu) > } > > write_sysreg_el2(*vcpu_pc(vcpu), elr); > + > + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { > + vcpu->arch.fault.esr_el2 = > + (ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT) | 0x22; > + return false; > + } else { > + return true; > + } > } > > int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) > @@ -342,13 +355,21 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) > int ret = __vgic_v2_perform_cpuif_access(vcpu); > > if (ret == 1) { > - __skip_instr(vcpu); > - goto again; > + if (__skip_instr(vcpu)) > + goto again; > + else > + exit_code = ARM_EXCEPTION_TRAP; > } > > if (ret == -1) { > - /* Promote an illegal access to an SError */ > - __skip_instr(vcpu); > + /* Promote an illegal access to an > + * SError. If we would be returning > + * due to single-step clear the SS > + * bit so handle_exit knows what to > + * do after dealing with the error. > + */ > + if (!__skip_instr(vcpu)) > + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; > exit_code = ARM_EXCEPTION_EL1_SERROR; > } > > @@ -363,8 +384,10 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) > int ret = __vgic_v3_perform_cpuif_access(vcpu); > > if (ret == 1) { > - __skip_instr(vcpu); > - goto again; > + if (__skip_instr(vcpu)) > + goto again; > + else > + exit_code = ARM_EXCEPTION_TRAP; > } > > /* 0 falls through to be handled out of EL2 */ > -- > 2.15.0 > Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c index 525c01f48867..f7c651f3a8c0 100644 --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -22,6 +22,7 @@ #include <asm/kvm_emulate.h> #include <asm/kvm_hyp.h> #include <asm/fpsimd.h> +#include <asm/debug-monitors.h> static bool __hyp_text __fpsimd_enabled_nvhe(void) { @@ -269,7 +270,11 @@ static bool __hyp_text __populate_fault_info(struct kvm_vcpu *vcpu) return true; } -static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu) +/* Skip an instruction which has been emulated. Returns true if + * execution can continue or false if we need to exit hyp mode because + * single-step was in effect. + */ +static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu) { *vcpu_pc(vcpu) = read_sysreg_el2(elr); @@ -282,6 +287,14 @@ static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu) } write_sysreg_el2(*vcpu_pc(vcpu), elr); + + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { + vcpu->arch.fault.esr_el2 = + (ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT) | 0x22; + return false; + } else { + return true; + } } int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) @@ -342,13 +355,21 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) int ret = __vgic_v2_perform_cpuif_access(vcpu); if (ret == 1) { - __skip_instr(vcpu); - goto again; + if (__skip_instr(vcpu)) + goto again; + else + exit_code = ARM_EXCEPTION_TRAP; } if (ret == -1) { - /* Promote an illegal access to an SError */ - __skip_instr(vcpu); + /* Promote an illegal access to an + * SError. If we would be returning + * due to single-step clear the SS + * bit so handle_exit knows what to + * do after dealing with the error. + */ + if (!__skip_instr(vcpu)) + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; exit_code = ARM_EXCEPTION_EL1_SERROR; } @@ -363,8 +384,10 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) int ret = __vgic_v3_perform_cpuif_access(vcpu); if (ret == 1) { - __skip_instr(vcpu); - goto again; + if (__skip_instr(vcpu)) + goto again; + else + exit_code = ARM_EXCEPTION_TRAP; } /* 0 falls through to be handled out of EL2 */
There is a fast-path of MMIO emulation inside hyp mode. The handling of single-step is broadly the same as kvm_arm_handle_step_debug() except we just setup ESR/HSR so handle_exit() does the correct thing as we exit. For the case of an emulated illegal access causing an SError we will exit via the ARM_EXCEPTION_EL1_SERROR path in handle_exit(). We behave as we would during a real SError and clear the DBG_SPSR_SS bit for the emulated instruction. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- arch/arm64/kvm/hyp/switch.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) -- 2.15.0