| Message ID | 1431700035-23479-7-git-send-email-alex.bennee@linaro.org |
|---|---|
| State | New |
| Headers | show |
Will Deacon <will.deacon@arm.com> writes: > Hi Alex, > > On Fri, May 15, 2015 at 03:27:09PM +0100, Alex Bennée wrote: >> This adds support for SW breakpoints inserted by userspace. >> >> We do this by trapping all guest software debug exceptions to the >> hypervisor (MDCR_EL2.TDE). The exit handler sets an exit reason of >> KVM_EXIT_DEBUG with the kvm_debug_exit_arch structure holding the >> exception syndrome information. >> >> It will be up to userspace to extract the PC (via GET_ONE_REG) and >> determine if the debug event was for a breakpoint it inserted. If not >> userspace will need to re-inject the correct exception restart the >> hypervisor to deliver the debug exception to the guest. >> >> Any other guest software debug exception (e.g. single step or HW >> assisted breakpoints) will cause an error and the VM to be killed. This >> is addressed by later patches which add support for the other debug >> types. >> >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> >> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> >> >> --- >> v2 >> - update to use new exit struct >> - tweak for C setup >> - do our setup in debug_setup/clear code >> - fixed up comments >> v3: >> - fix spacing in KVM_GUESTDBG_VALID_MASK >> - fix and clarify wording on kvm_handle_guest_debug >> - handle error case in kvm_handle_guest_debug >> - re-word the commit message >> v4 >> - rm else leg >> - add r-b-tag >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index ba635c7..33c8143 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt > > Not sure why, but your patches seem to drop the diffstat which makes it > slightly more onerous for reviewers trying to figure out which bits touch > their trees. Are you removing it manually? No - I'm running: git pps -v 4 origin/master..HEAD -o guestdbg.patches Where pps is an alias: pps = format-patch --cover-letter --summary Manually expanding the alias gives the same results. I'll have a dig to see what's going on. > > Will
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index ba635c7..33c8143 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -2667,7 +2667,7 @@ when running. Common control bits are: The top 16 bits of the control field are architecture specific control flags which can include the following: - - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86] + - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64] - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390] - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86] - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86] diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index 4a274e1..064c105 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -302,7 +302,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) kvm_arm_set_running_vcpu(NULL); } -#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE) +#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP) /** * kvm_arch_vcpu_ioctl_set_guest_debug - set up guest debugging diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index faf0e1f..8d1bfa4 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -73,6 +73,9 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) if (trap_debug) vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; + /* Trap breakpoints? */ + if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) + vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; } void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index 524fa25..27f38a9 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -82,6 +82,40 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run) return 1; } +/** + * kvm_handle_guest_debug - handle a debug exception instruction + * + * @vcpu: the vcpu pointer + * @run: access to the kvm_run structure for results + * + * We route all debug exceptions through the same handler. If both the + * guest and host are using the same debug facilities it will be up to + * userspace to re-inject the correct exception for guest delivery. + * + * @return: 0 (while setting run->exit_reason), -1 for error + */ +static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run) +{ + u32 hsr = kvm_vcpu_get_hsr(vcpu); + int ret = 0; + + run->exit_reason = KVM_EXIT_DEBUG; + run->debug.arch.hsr = hsr; + + switch (hsr >> ESR_ELx_EC_SHIFT) { + case ESR_ELx_EC_BKPT32: + case ESR_ELx_EC_BRK64: + break; + default: + kvm_err("%s: un-handled case hsr: %#08x\n", + __func__, (unsigned int) hsr); + ret = -1; + break; + } + + return ret; +} + static exit_handle_fn arm_exit_handlers[] = { [ESR_ELx_EC_WFx] = kvm_handle_wfx, [ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32, @@ -96,6 +130,8 @@ 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_BKPT32] = kvm_handle_guest_debug, + [ESR_ELx_EC_BRK64] = kvm_handle_guest_debug, }; static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)