| Message ID | 1430929407-3487-8-git-send-email-alex.bennee@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, May 06, 2015 at 05:23:22PM +0100, Alex Bennée wrote: > This adds support for single-stepping the guest. To do this we need to > manipulate the guests PSTATE.SS and MDSCR_EL1.SS bits which we do in the > kvm_arm_setup/clear_debug() so we don't affect the apparent state of the > guest. Additionally while the host is debugging the guest we suppress > the ability of the guest to single-step itself. > > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > > --- > v2 > - Move pstate/mdscr manipulation into C > - don't export guest_debug to assembly > - add accessor for saved_debug regs > - tweak save/restore of mdscr_el1 > v3 > - don't save PC in debug information struct > - rename debug_saved_regs->guest_debug_state > - save whole value, only use bits in restore > - add save/restore_guest-debug_regs helper functions > - simplify commit message for clarity > - rm vcpu_debug_saved_reg access fn > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index 064c105..9b3ed6d 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -302,7 +302,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > kvm_arm_set_running_vcpu(NULL); > } > > -#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP) > +#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \ > + KVM_GUESTDBG_USE_SW_BP | \ > + KVM_GUESTDBG_SINGLESTEP) > > /** > * kvm_arch_vcpu_ioctl_set_guest_debug - set up guest debugging > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 7cb99b5..b60fa7a 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -123,6 +123,12 @@ struct kvm_vcpu_arch { > * here. > */ > > + /* Guest registers we preserve during guest debugging */ > + struct { > + u32 pstate; This could do a with a comment: /* preserve SPSR_DEBUG_MASK bits */ > + u32 mdscr_el1; > + } guest_debug_state; > + > /* Don't run the guest */ > bool pause; > > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > index 5bee676..19346e8 100644 > --- a/arch/arm64/kvm/debug.c > +++ b/arch/arm64/kvm/debug.c > @@ -19,11 +19,42 @@ > > #include <linux/kvm_host.h> > > +#include <asm/debug-monitors.h> > +#include <asm/kvm_asm.h> > #include <asm/kvm_arm.h> > +#include <asm/kvm_emulate.h> > + > +/* These are the bits of MDSCR_EL1 we may manipulate */ > +#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \ > + DBG_MDSCR_KDE | \ > + DBG_MDSCR_MDE) > + > +#define SPSR_DEBUG_MASK DBG_SPSR_SS > > static DEFINE_PER_CPU(u32, mdcr_el2); > > /** > + * save/restore_guest_debug_regs > + * > + * For some debug operations we need to tweak some guest registers. As > + * a result we need to save the state of those registers before we > + * make those modifications. > + */ > +static void save_guest_debug_regs(struct kvm_vcpu *vcpu) > +{ > + vcpu->arch.guest_debug_state.pstate = *vcpu_cpsr(vcpu); > + vcpu->arch.guest_debug_state.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1); > +} > + > +static void restore_guest_debug_regs(struct kvm_vcpu *vcpu) > +{ > + *vcpu_cpsr(vcpu) |= > + (vcpu->arch.guest_debug_state.pstate & SPSR_DEBUG_MASK); > + vcpu_sys_reg(vcpu, MDSCR_EL1) |= > + (vcpu->arch.guest_debug_state.mdscr_el1 & MDSCR_EL1_DEBUG_MASK); This doesn't look right. Don't you need to also clear the values if they were set by us for single-stepping the guest? At least for the MDSCR_EL1.SS bit. What if we're single-stepping through guest code that modifies the SS bits of these register for the guest state? Is that possible and do we capture this somehow? > +} > + > +/** > * kvm_arm_init_debug - grab what we need for debug > * > * Currently the sole task of this function is to retrieve the initial > @@ -38,7 +69,6 @@ void kvm_arm_init_debug(void) > __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2)); > } > > - > /** > * kvm_arm_setup_debug - set up debug related stuff > * > @@ -75,15 +105,37 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) > else > vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDA; > > - /* Trap breakpoints? */ > - if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) > + /* Is Guest debugging in effect? */ > + if (vcpu->guest_debug) { you could have just checked the field like this in the original patch, but ok. > vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; > - else > - vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; > > + /* Save guest debug state */ > + save_guest_debug_regs(vcpu); > + > + /* > + * Single Step (ARM ARM D2.12.3 The software step state > + * machine) > + * > + * If we are doing Single Step we need to manipulate > + * MDSCR_EL1.SS and PSTATE.SS. If not we need to > + * suppress the guests ability to trigger single step itself. > + */ > + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { > + *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; > + vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS; > + } else { > + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; why must we clear PSTATE.SS when we have MDSCR_EL1.SS == 0 ? > + vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS; > + } > + > + } else { > + /* Debug operations can go straight to the guest */ > + vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; still don't think you need this. > + } > } > > void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) > { > - /* Nothing to do yet */ > + if (vcpu->guest_debug) > + restore_guest_debug_regs(vcpu); > } > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index 27f38a9..e9de13e 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -103,6 +103,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run) > run->debug.arch.hsr = hsr; > > switch (hsr >> ESR_ELx_EC_SHIFT) { > + case ESR_ELx_EC_SOFTSTP_LOW: > case ESR_ELx_EC_BKPT32: > case ESR_ELx_EC_BRK64: > break; > @@ -130,6 +131,7 @@ static exit_handle_fn arm_exit_handlers[] = { > [ESR_ELx_EC_SYS64] = kvm_handle_sys_reg, > [ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort, > [ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort, > + [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug, > [ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug, > [ESR_ELx_EC_BRK64] = kvm_handle_guest_debug, > }; > -- > 2.3.5 > Thanks, -Christoffer
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index 064c105..9b3ed6d 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -302,7 +302,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) kvm_arm_set_running_vcpu(NULL); } -#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP) +#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \ + KVM_GUESTDBG_USE_SW_BP | \ + KVM_GUESTDBG_SINGLESTEP) /** * kvm_arch_vcpu_ioctl_set_guest_debug - set up guest debugging diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 7cb99b5..b60fa7a 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -123,6 +123,12 @@ struct kvm_vcpu_arch { * here. */ + /* Guest registers we preserve during guest debugging */ + struct { + u32 pstate; + u32 mdscr_el1; + } guest_debug_state; + /* Don't run the guest */ bool pause; diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index 5bee676..19346e8 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -19,11 +19,42 @@ #include <linux/kvm_host.h> +#include <asm/debug-monitors.h> +#include <asm/kvm_asm.h> #include <asm/kvm_arm.h> +#include <asm/kvm_emulate.h> + +/* These are the bits of MDSCR_EL1 we may manipulate */ +#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \ + DBG_MDSCR_KDE | \ + DBG_MDSCR_MDE) + +#define SPSR_DEBUG_MASK DBG_SPSR_SS static DEFINE_PER_CPU(u32, mdcr_el2); /** + * save/restore_guest_debug_regs + * + * For some debug operations we need to tweak some guest registers. As + * a result we need to save the state of those registers before we + * make those modifications. + */ +static void save_guest_debug_regs(struct kvm_vcpu *vcpu) +{ + vcpu->arch.guest_debug_state.pstate = *vcpu_cpsr(vcpu); + vcpu->arch.guest_debug_state.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1); +} + +static void restore_guest_debug_regs(struct kvm_vcpu *vcpu) +{ + *vcpu_cpsr(vcpu) |= + (vcpu->arch.guest_debug_state.pstate & SPSR_DEBUG_MASK); + vcpu_sys_reg(vcpu, MDSCR_EL1) |= + (vcpu->arch.guest_debug_state.mdscr_el1 & MDSCR_EL1_DEBUG_MASK); +} + +/** * kvm_arm_init_debug - grab what we need for debug * * Currently the sole task of this function is to retrieve the initial @@ -38,7 +69,6 @@ void kvm_arm_init_debug(void) __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2)); } - /** * kvm_arm_setup_debug - set up debug related stuff * @@ -75,15 +105,37 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) else vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDA; - /* Trap breakpoints? */ - if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) + /* Is Guest debugging in effect? */ + if (vcpu->guest_debug) { vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; - else - vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; + /* Save guest debug state */ + save_guest_debug_regs(vcpu); + + /* + * Single Step (ARM ARM D2.12.3 The software step state + * machine) + * + * If we are doing Single Step we need to manipulate + * MDSCR_EL1.SS and PSTATE.SS. If not we need to + * suppress the guests ability to trigger single step itself. + */ + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { + *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; + vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS; + } else { + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; + vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS; + } + + } else { + /* Debug operations can go straight to the guest */ + vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; + } } void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) { - /* Nothing to do yet */ + if (vcpu->guest_debug) + restore_guest_debug_regs(vcpu); } diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index 27f38a9..e9de13e 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -103,6 +103,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run) run->debug.arch.hsr = hsr; switch (hsr >> ESR_ELx_EC_SHIFT) { + case ESR_ELx_EC_SOFTSTP_LOW: case ESR_ELx_EC_BKPT32: case ESR_ELx_EC_BRK64: break; @@ -130,6 +131,7 @@ static exit_handle_fn arm_exit_handlers[] = { [ESR_ELx_EC_SYS64] = kvm_handle_sys_reg, [ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort, [ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort, + [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug, [ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug, [ESR_ELx_EC_BRK64] = kvm_handle_guest_debug, };
This adds support for single-stepping the guest. To do this we need to manipulate the guests PSTATE.SS and MDSCR_EL1.SS bits which we do in the kvm_arm_setup/clear_debug() so we don't affect the apparent state of the guest. Additionally while the host is debugging the guest we suppress the ability of the guest to single-step itself. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- v2 - Move pstate/mdscr manipulation into C - don't export guest_debug to assembly - add accessor for saved_debug regs - tweak save/restore of mdscr_el1 v3 - don't save PC in debug information struct - rename debug_saved_regs->guest_debug_state - save whole value, only use bits in restore - add save/restore_guest-debug_regs helper functions - simplify commit message for clarity - rm vcpu_debug_saved_reg access fn