From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v6 10/12] KVM: arm64: guest debug, HW assisted debug support Date: Wed, 24 Jun 2015 22:22:16 +0200 Message-ID: <20150624202216.GE22785@cbox> References: <1434716630-18260-1-git-send-email-alex.bennee@linaro.org> <1434716630-18260-11-git-send-email-alex.bennee@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1434716630-18260-11-git-send-email-alex.bennee-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org, marc.zyngier-5wv7dgnIgG8@public.gmane.org, peter.maydell-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, agraf-l3A5Bk7waGM@public.gmane.org, drjones-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, zhichao.huang-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, jan.kiszka-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org, dahi-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, r65777-KZfg59tc24xl57MIdRCFDg@public.gmane.org, bp-l3A5Bk7waGM@public.gmane.org, Gleb Natapov , Jonathan Corbet , Russell King , Catalin Marinas , Will Deacon , Peter Zijlstra , Lorenzo Pieralisi , Ingo Molnar , "open list:DOCUMENTATION" , open list , "open list:ABI/API" List-Id: linux-api@vger.kernel.org On Fri, Jun 19, 2015 at 01:23:48PM +0100, Alex Benn=E9e wrote: > This adds support for userspace to control the HW debug registers for > guest debug. In the debug ioctl we copy the IMPDEF defined number of s/defined// > registers into a new register set called host_debug_state. There is n= ow > a new vcpu parameter called debug_ptr which selects which register se= t > is to copied into the real registers when world switch occurs. But this patch doesn't seem to add the debug_ptr field? s/to// >=20 > I've moved some helper functions into the hw_breakpoint.h header for > re-use. >=20 > As with single step we need to tweak the guest registers to enable th= e > exceptions so we need to save and restore those bits. >=20 > Two new capabilities have been added to the KVM_EXTENSION ioctl to al= low > userspace to query the number of hardware break and watch points > available on the host hardware. >=20 > Signed-off-by: Alex Benn=E9e >=20 > --- > v2 > - switched to C setup > - replace host debug registers directly into context > - minor tweak to api docs > - setup right register for debug > - add FAR_EL2 to debug exit structure > - add support for trapping debug register access > v3 > - remove stray trace statement > - fix spacing around operators (various) > - clean-up usage of trap_debug > - introduce debug_ptr, replace excessive memcpy stuff > - don't use memcpy in ioctl, just assign > - update cap ioctl documentation > - reword a number comments > - rename host_debug_state->external_debug_state > v4 > - use the new u32/u64 split debug_ptr approach > - fix some wording/comments > v5 > - don't set MDSCR_EL1.KDE (not needed) > v6 > - update wording given change in commentary > - KVM_GUESTDBG_USE_HW_BP->KVM_GUESTDBG_USE_HW > --- > Documentation/virtual/kvm/api.txt | 7 ++++++- > arch/arm/kvm/arm.c | 7 +++++++ > arch/arm64/include/asm/hw_breakpoint.h | 12 +++++++++++ > arch/arm64/include/asm/kvm_host.h | 6 +++++- > arch/arm64/kernel/hw_breakpoint.c | 12 ----------- > arch/arm64/kvm/debug.c | 37 ++++++++++++++++++++++++= +++++----- > arch/arm64/kvm/handle_exit.c | 6 ++++++ > arch/arm64/kvm/reset.c | 12 +++++++++++ > include/uapi/linux/kvm.h | 2 ++ > 9 files changed, 82 insertions(+), 19 deletions(-) >=20 > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtua= l/kvm/api.txt > index 33c8143..ada57df 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -2668,7 +2668,7 @@ The top 16 bits of the control field are archit= ecture specific control > flags which can include the following: > =20 > - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm= 64] > - - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s39= 0] > + - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s39= 0, arm64] > - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86] > - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86] > - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s39= 0] > @@ -2683,6 +2683,11 @@ updated to the correct (supplied) values. > The second part of the structure is architecture specific and > typically contains a set of debug registers. > =20 > +For arm64 the number of debug registers is implementation defined an= d > +can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and > +KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive numb= er > +indicating the number of supported registers. > + > When debug events exit the main run loop with the reason > KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run > structure containing architecture specific debug information. > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index 0d17c7b..60c4045 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -307,6 +307,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > =20 > #define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \ > KVM_GUESTDBG_USE_SW_BP | \ > + KVM_GUESTDBG_USE_HW | \ > KVM_GUESTDBG_SINGLESTEP) > =20 > /** > @@ -327,6 +328,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct k= vm_vcpu *vcpu, > =20 > if (dbg->control & KVM_GUESTDBG_ENABLE) { > vcpu->guest_debug =3D dbg->control; > + > + /* Hardware assisted Break and Watch points */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { > + vcpu->arch.external_debug_state =3D dbg->arch; > + } > + > } else { > /* If not enabled clear all flags */ > vcpu->guest_debug =3D 0; > diff --git a/arch/arm64/include/asm/hw_breakpoint.h b/arch/arm64/incl= ude/asm/hw_breakpoint.h > index 52b484b..c450552 100644 > --- a/arch/arm64/include/asm/hw_breakpoint.h > +++ b/arch/arm64/include/asm/hw_breakpoint.h > @@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct = task_struct *task) > } > #endif > =20 > +/* Determine number of BRP registers available. */ > +static inline int get_num_brps(void) > +{ > + return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1; > +} > + > +/* Determine number of WRP registers available. */ > +static inline int get_num_wrps(void) > +{ > + return ((read_cpuid(ID_AA64DFR0_EL1) >> 20) & 0xf) + 1; > +} > + > extern struct pmu perf_ops_bp; > =20 > #endif /* __KERNEL__ */ > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/a= sm/kvm_host.h > index 9697daf..0a3ee7b 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -116,13 +116,17 @@ struct kvm_vcpu_arch { > * debugging the guest from the host and to maintain separate host = and > * guest state during world switches. vcpu_debug_state are the debu= g > * registers of the vcpu as the guest sees them. host_debug_state = are > - * the host registers which are saved and restored during world swi= tches. > + * the host registers which are saved and restored during > + * world switches. external_debug_state contains the debug > + * values we want to debugging the guest. This is set via the nit: s/debugging/debug/ > + * KVM_SET_GUEST_DEBUG ioctl. > * > * debug_ptr points to the set of debug registers that should be lo= aded > * onto the hardware when running the guest. > */ > struct kvm_guest_debug_arch *debug_ptr; > struct kvm_guest_debug_arch vcpu_debug_state; > + struct kvm_guest_debug_arch external_debug_state; > =20 > /* Pointer to host CPU context */ > kvm_cpu_context_t *host_cpu_context; > diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw= _breakpoint.c > index e7d934d..3a41bbf 100644 > --- a/arch/arm64/kernel/hw_breakpoint.c > +++ b/arch/arm64/kernel/hw_breakpoint.c > @@ -49,18 +49,6 @@ static DEFINE_PER_CPU(int, stepping_kernel_bp); > static int core_num_brps; > static int core_num_wrps; > =20 > -/* Determine number of BRP registers available. */ > -static int get_num_brps(void) > -{ > - return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1; > -} > - > -/* Determine number of WRP registers available. */ > -static int get_num_wrps(void) > -{ > - return ((read_cpuid(ID_AA64DFR0_EL1) >> 20) & 0xf) + 1; > -} > - > int hw_breakpoint_slots(int type) > { > /* > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > index d439eb8..b287bbc 100644 > --- a/arch/arm64/kvm/debug.c > +++ b/arch/arm64/kvm/debug.c > @@ -96,10 +96,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) > MDCR_EL2_TDRA | > MDCR_EL2_TDOSA); > =20 > - /* Trap on access to debug registers? */ > - if (trap_debug) > - vcpu->arch.mdcr_el2 |=3D MDCR_EL2_TDA; > - > /* Is Guest debugging in effect? */ > if (vcpu->guest_debug) { > /* Route all software debug exceptions to EL2 */ > @@ -134,11 +130,42 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) > } else { > vcpu_sys_reg(vcpu, MDSCR_EL1) &=3D ~DBG_MDSCR_SS; > } > + > + /* > + * HW Breakpoints and watchpoints > + * > + * We simply switch the debug_ptr to point to our new > + * external_debug_state which has been populated by the > + * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY > + * mechanism ensures the registers are updated on the > + * world switch. > + */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { > + /* Enable breakpoints/watchpoints */ > + vcpu_sys_reg(vcpu, MDSCR_EL1) |=3D DBG_MDSCR_MDE; > + > + vcpu->arch.debug_ptr =3D &vcpu->arch.external_debug_state; > + vcpu->arch.debug_flags |=3D KVM_ARM64_DEBUG_DIRTY; > + trap_debug =3D true; > + } > } > + > + /* Trap debug register access */ > + if (trap_debug) > + vcpu->arch.mdcr_el2 |=3D MDCR_EL2_TDA; > } > =20 > void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) > { > - if (vcpu->guest_debug) > + if (vcpu->guest_debug) { > restore_guest_debug_regs(vcpu); > + > + /* > + * If we were using HW debug we need to restore the > + * debug_ptr to the guest debug state. > + */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) > + vcpu->arch.debug_ptr =3D &vcpu->arch.vcpu_debug_state; I still think this would be more cleanly done in the setup_debug function, but ok: Reviewed-by: Christoffer Dall