Re: [RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On Tue, 7 Jan 2020 at 21:37, Beata Michalska wrote: > > On Tue, 7 Jan 2020 at 14:28, Peter Maydell wrote: > > Another thing that occurred to me last night -- why do we need > > to do this adjustment of the PC/r15 ? If this is the kernel > > handing control to userspace to say "this is not an instruction > > I can handle, maybe you'd like to try" then surely it should > > do so with the PC pointing at the offending instruction? > > Similarly, if we ask the kernel to inject a data abort I > > would expect that the kernel would do the work of adjusting > > the PC forwards as the architecture requires when taking > > the exception. > > > > The code here is just for easing debugging from Qemu perspective > and that is the only reason why we even try to read the value of PC > - it is not in any way needed by kernel to inject the abort. > One can use the monitor to decode the instruction, provided it is still > available at the memory location pointed by PC (handy monitor_disas) > - that is why logging the address with decoded instruction, > as it is the only thing that is being done here. Still the address of actually > executed instruction for ARM would be PC–8 (PC–4 for Thumb) > that's why the adjustment. My point is that the kernel hasn't actually executed the instruction, though -- that's why it's given us control. It seems a bit exposing of the underlying hw mechanism for the kernel to hand control back to userspace with the vcpu state in a sort of half-way-through situation, rather than cleanly rolling it back to "this insn has not executed at all yet". thanks -- PMM
Re: [RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On Tue, 7 Jan 2020 at 14:28, Peter Maydell wrote: > > On Fri, 20 Dec 2019 at 20:27, Beata Michalska > wrote: > > > > On ARMv7 & ARMv8 some load/store instructions might trigger a data abort > > exception with no valid ISS info to be decoded. The lack of decode info > > makes it at least tricky to emulate those instruction which is one of the > > (many) reasons why KVM will not even try to do so. > > > > Add suport for handling those by requesting KVM to inject external > > dabt into the quest. > > > > Signed-off-by: Beata Michalska > > --- > > +/* > > + * Get current PC before it will get updated to except vector entry > > + */ > > +target_ulong ins_addr = is_a64(env) ? env->pc > > +/* AArch32 mode vs T32 aka Thumb mode */ > > +: env->regs[15] - (env->thumb ? 4 : 8); > > Another thing that occurred to me last night -- why do we need > to do this adjustment of the PC/r15 ? If this is the kernel > handing control to userspace to say "this is not an instruction > I can handle, maybe you'd like to try" then surely it should > do so with the PC pointing at the offending instruction? > Similarly, if we ask the kernel to inject a data abort I > would expect that the kernel would do the work of adjusting > the PC forwards as the architecture requires when taking > the exception. > The code here is just for easing debugging from Qemu perspective and that is the only reason why we even try to read the value of PC - it is not in any way needed by kernel to inject the abort. One can use the monitor to decode the instruction, provided it is still available at the memory location pointed by PC (handy monitor_disas) - that is why logging the address with decoded instruction, as it is the only thing that is being done here. Still the address of actually executed instruction for ARM would be PC–8 (PC–4 for Thumb) that's why the adjustment. BR Beata > thanks > -- PMM
Re: [RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On Fri, 20 Dec 2019 at 20:27, Beata Michalska wrote: > > On ARMv7 & ARMv8 some load/store instructions might trigger a data abort > exception with no valid ISS info to be decoded. The lack of decode info > makes it at least tricky to emulate those instruction which is one of the > (many) reasons why KVM will not even try to do so. > > Add suport for handling those by requesting KVM to inject external > dabt into the quest. > > Signed-off-by: Beata Michalska > --- > +/* > + * Get current PC before it will get updated to except vector entry > + */ > +target_ulong ins_addr = is_a64(env) ? env->pc > +/* AArch32 mode vs T32 aka Thumb mode */ > +: env->regs[15] - (env->thumb ? 4 : 8); Another thing that occurred to me last night -- why do we need to do this adjustment of the PC/r15 ? If this is the kernel handing control to userspace to say "this is not an instruction I can handle, maybe you'd like to try" then surely it should do so with the PC pointing at the offending instruction? Similarly, if we ask the kernel to inject a data abort I would expect that the kernel would do the work of adjusting the PC forwards as the architecture requires when taking the exception. thanks -- PMM
Re: [RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On Mon, 6 Jan 2020 at 17:15, Peter Maydell wrote:
>
> On Fri, 20 Dec 2019 at 20:27, Beata Michalska
> wrote:
> >
> > On ARMv7 & ARMv8 some load/store instructions might trigger a data abort
> > exception with no valid ISS info to be decoded. The lack of decode info
> > makes it at least tricky to emulate those instruction which is one of the
> > (many) reasons why KVM will not even try to do so.
> >
> > Add suport for handling those by requesting KVM to inject external
> > dabt into the quest.
> >
> > Signed-off-by: Beata Michalska
> > ---
> > accel/kvm/kvm-all.c| 15 +++
> > accel/stubs/kvm-stub.c | 4 ++
> > include/sysemu/kvm.h | 1 +
> > target/arm/cpu.h | 3 +-
> > target/arm/kvm.c | 95 ++
> > target/arm/kvm32.c | 3 ++
> > target/arm/kvm64.c | 3 ++
> > target/arm/kvm_arm.h | 19 +
> > 8 files changed, 142 insertions(+), 1 deletion(-)
> >
> > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> > index ca00daa2f5..a3ee038142 100644
> > --- a/accel/kvm/kvm-all.c
> > +++ b/accel/kvm/kvm-all.c
> > @@ -2174,6 +2174,14 @@ static void do_kvm_cpu_synchronize_state(CPUState
> > *cpu, run_on_cpu_data arg)
> > }
> > }
> >
> > +static void do_kvm_cpu_synchronize_state_force(CPUState *cpu,
> > + run_on_cpu_data arg)
> > +{
> > +kvm_arch_get_registers(cpu);
> > +cpu->vcpu_dirty = true;
> > +}
>
> Why is this functionality special such that it needs a non-standard
> way of synchronizing state with KVM that nothing else does ?
We need the up-to-date state when handling the NISV and this is being
achieved by calling synchronise cpu state. This will set the 'dirty' flag,
as expected. In order to get KVM to insert the external abort we need to
set vcpu events. So far so good. Still, as the cpu state is marked as 'dirty',
before entering the KVM_RUN again, Qemu will overwrite relevant regs
-> see kvm_arch_put_registers. This messes up with the regs
setup done by KVM when injecting the external abort. This is why we need
a sequence:
sync vcpu -> put events -> sync vcpu again
so that when entering KVM_RUN Qemu has all the updates needed.
Now, I could just set the 'dirty' flag to false and skip the regular
kvm_arch_put_registers after setting the vcpu event,
but it seemed more sensible to have the sync version that despite the dirty
flag performs the requested sync. This is just to avoid hacky way
round the problem.
I was tempted to re-factor slightly syncing regs and events but that seemed
too invasive for this particular change. I might try to do just that though.
>
> > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> > index 9fe233b9bf..0cacc61d8a 100644
> > --- a/include/sysemu/kvm.h
> > +++ b/include/sysemu/kvm.h
> > @@ -483,6 +483,7 @@ void kvm_cpu_synchronize_state(CPUState *cpu);
> > void kvm_cpu_synchronize_post_reset(CPUState *cpu);
> > void kvm_cpu_synchronize_post_init(CPUState *cpu);
> > void kvm_cpu_synchronize_pre_loadvm(CPUState *cpu);
> > +void kvm_cpu_synchronize_state_force(CPUState *cpu);
> >
> > void kvm_init_cpu_signals(CPUState *cpu);
> >
> > diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> > index 5f70e9e043..e11b5e7438 100644
> > --- a/target/arm/cpu.h
> > +++ b/target/arm/cpu.h
> > @@ -558,7 +558,8 @@ typedef struct CPUARMState {
> > uint8_t has_esr;
> > uint64_t esr;
> > } serror;
> > -
> > +/* Status field for pending extarnal dabt */
>
> "external" (I think you have the same typo later in the patch too)
And I did run the codespell ... Will blame it on Christmas rush ...
And will fix all the typos.
>
> > +uint8_t ext_dabt_pending;
> > /* State of our input IRQ/FIQ/VIRQ/VFIQ lines */
> > uint32_t irq_line_state;
>
>
> > @@ -701,6 +719,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
> > *run)
> > ret = EXCP_DEBUG;
> > } /* otherwise return to guest */
> > break;
> > +case KVM_EXIT_ARM_NISV:
> > +/* External DAB with no valid iss to decode */
>
> "DABT"
>
> > +ret = kvm_arm_handle_dabt_nisv(cs, run->arm_nisv.esr_iss,
> > + run->arm_nisv.fault_ipa);
>
> (indentation looks odd here?)
It does indeed
>
> > +break;
> > default:
> > qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
> >__func__, run->exit_reason);
> > @@ -835,3 +858,75 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> > {
> > return (data - 32) & 0x;
> > }
> > +
> > +int kvm_arm_handle_dabt_nisv(CPUState *cs, uint64_t esr_iss,
> > + uint64_t fault_ipa)
> > +{
> > +ARMCPU *cpu = ARM_CPU(cs);
> > +CPUARMState *env = &cpu->env;
> > +hwaddr xlat, len;
> > +AddressSpace *as = cs->as ? cs->as : &address_space_memory;
>
> I don't think you should need to test cs->as for NULL;
> qemu_init_vcpu() ensures that one is alwa
Re: [RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On Fri, 20 Dec 2019 at 20:27, Beata Michalska
wrote:
>
> On ARMv7 & ARMv8 some load/store instructions might trigger a data abort
> exception with no valid ISS info to be decoded. The lack of decode info
> makes it at least tricky to emulate those instruction which is one of the
> (many) reasons why KVM will not even try to do so.
>
> Add suport for handling those by requesting KVM to inject external
> dabt into the quest.
>
> Signed-off-by: Beata Michalska
> ---
> accel/kvm/kvm-all.c| 15 +++
> accel/stubs/kvm-stub.c | 4 ++
> include/sysemu/kvm.h | 1 +
> target/arm/cpu.h | 3 +-
> target/arm/kvm.c | 95 ++
> target/arm/kvm32.c | 3 ++
> target/arm/kvm64.c | 3 ++
> target/arm/kvm_arm.h | 19 +
> 8 files changed, 142 insertions(+), 1 deletion(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index ca00daa2f5..a3ee038142 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2174,6 +2174,14 @@ static void do_kvm_cpu_synchronize_state(CPUState
> *cpu, run_on_cpu_data arg)
> }
> }
>
> +static void do_kvm_cpu_synchronize_state_force(CPUState *cpu,
> + run_on_cpu_data arg)
> +{
> +kvm_arch_get_registers(cpu);
> +cpu->vcpu_dirty = true;
> +}
Why is this functionality special such that it needs a non-standard
way of synchronizing state with KVM that nothing else does ?
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index 9fe233b9bf..0cacc61d8a 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -483,6 +483,7 @@ void kvm_cpu_synchronize_state(CPUState *cpu);
> void kvm_cpu_synchronize_post_reset(CPUState *cpu);
> void kvm_cpu_synchronize_post_init(CPUState *cpu);
> void kvm_cpu_synchronize_pre_loadvm(CPUState *cpu);
> +void kvm_cpu_synchronize_state_force(CPUState *cpu);
>
> void kvm_init_cpu_signals(CPUState *cpu);
>
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 5f70e9e043..e11b5e7438 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -558,7 +558,8 @@ typedef struct CPUARMState {
> uint8_t has_esr;
> uint64_t esr;
> } serror;
> -
> +/* Status field for pending extarnal dabt */
"external" (I think you have the same typo later in the patch too)
> +uint8_t ext_dabt_pending;
> /* State of our input IRQ/FIQ/VIRQ/VFIQ lines */
> uint32_t irq_line_state;
> @@ -701,6 +719,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
> *run)
> ret = EXCP_DEBUG;
> } /* otherwise return to guest */
> break;
> +case KVM_EXIT_ARM_NISV:
> +/* External DAB with no valid iss to decode */
"DABT"
> +ret = kvm_arm_handle_dabt_nisv(cs, run->arm_nisv.esr_iss,
> + run->arm_nisv.fault_ipa);
(indentation looks odd here?)
> +break;
> default:
> qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
>__func__, run->exit_reason);
> @@ -835,3 +858,75 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> {
> return (data - 32) & 0x;
> }
> +
> +int kvm_arm_handle_dabt_nisv(CPUState *cs, uint64_t esr_iss,
> + uint64_t fault_ipa)
> +{
> +ARMCPU *cpu = ARM_CPU(cs);
> +CPUARMState *env = &cpu->env;
> +hwaddr xlat, len;
> +AddressSpace *as = cs->as ? cs->as : &address_space_memory;
I don't think you should need to test cs->as for NULL;
qemu_init_vcpu() ensures that one is always set up.
Probably the neatest way to get the AddressSpace* is to
call arm_addressspace(cs, MEMTXATTRS_UNSPECIFIED).
> +int store_ins = ((esr_iss >> 6) & 1); /* WnR bit */
This should be a bool (matching the argument type for
address_space_translate), so you can just do
bool is_write = esr_iss & (1 << 6);
> +int ret;
> +
> +/*
> + * Note: The ioctl for SET_EVENTS will be triggered before next
> + * KVM_RUN call though the vcpu regs need to be updated before hand
> + * so to not to overwrite changes done by KVM upon injecting the abort.
> + * This sadly requires running sync twice - shame ...
> + */
> +kvm_cpu_synchronize_state(cs);
> + /*
> +* ISS [23:14] is invalid so there is a limited info
> +* on what has just happened so the only *useful* thing that can
> +* be retrieved from ISS is WnR & DFSC (though in some cases WnR
> +* might be less of a value as well)
> +*/
> +/* Verify whether the memory being accessed is even recognisable */
> +if (!address_space_translate(as, fault_ipa, &xlat, &len,
> + store_ins, MEMTXATTRS_UNSPECIFIED)) {
> +error_report("An attemp to access memory outside of the boundries"
"attempt"; "boundaries". But I think what we should actually report here
is:
"Guest attempted to access memory/device at guest physical address
0x... using an instruction that KVM could not em
[RFC PATCH 1/1] target/arm: kvm: Handle DABT with no valid ISS
On ARMv7 & ARMv8 some load/store instructions might trigger a data abort
exception with no valid ISS info to be decoded. The lack of decode info
makes it at least tricky to emulate those instruction which is one of the
(many) reasons why KVM will not even try to do so.
Add suport for handling those by requesting KVM to inject external
dabt into the quest.
Signed-off-by: Beata Michalska
---
accel/kvm/kvm-all.c| 15 +++
accel/stubs/kvm-stub.c | 4 ++
include/sysemu/kvm.h | 1 +
target/arm/cpu.h | 3 +-
target/arm/kvm.c | 95 ++
target/arm/kvm32.c | 3 ++
target/arm/kvm64.c | 3 ++
target/arm/kvm_arm.h | 19 +
8 files changed, 142 insertions(+), 1 deletion(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index ca00daa2f5..a3ee038142 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2174,6 +2174,14 @@ static void do_kvm_cpu_synchronize_state(CPUState *cpu,
run_on_cpu_data arg)
}
}
+static void do_kvm_cpu_synchronize_state_force(CPUState *cpu,
+ run_on_cpu_data arg)
+{
+kvm_arch_get_registers(cpu);
+cpu->vcpu_dirty = true;
+}
+
+
void kvm_cpu_synchronize_state(CPUState *cpu)
{
if (!cpu->vcpu_dirty) {
@@ -2181,6 +2189,13 @@ void kvm_cpu_synchronize_state(CPUState *cpu)
}
}
+void kvm_cpu_synchronize_state_force(CPUState *cpu)
+{
+/* Force the sync */
+run_on_cpu(cpu, do_kvm_cpu_synchronize_state_force, RUN_ON_CPU_NULL);
+}
+
+
static void do_kvm_cpu_synchronize_post_reset(CPUState *cpu, run_on_cpu_data
arg)
{
kvm_arch_put_registers(cpu, KVM_PUT_RESET_STATE);
diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
index 82f118d2df..e917d1d55e 100644
--- a/accel/stubs/kvm-stub.c
+++ b/accel/stubs/kvm-stub.c
@@ -58,6 +58,10 @@ void kvm_cpu_synchronize_post_init(CPUState *cpu)
{
}
+void kvm_cpu_synchronize_state_force(CPUState *cpu)
+{
+}
+
int kvm_cpu_exec(CPUState *cpu)
{
abort();
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 9fe233b9bf..0cacc61d8a 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -483,6 +483,7 @@ void kvm_cpu_synchronize_state(CPUState *cpu);
void kvm_cpu_synchronize_post_reset(CPUState *cpu);
void kvm_cpu_synchronize_post_init(CPUState *cpu);
void kvm_cpu_synchronize_pre_loadvm(CPUState *cpu);
+void kvm_cpu_synchronize_state_force(CPUState *cpu);
void kvm_init_cpu_signals(CPUState *cpu);
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 5f70e9e043..e11b5e7438 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -558,7 +558,8 @@ typedef struct CPUARMState {
uint8_t has_esr;
uint64_t esr;
} serror;
-
+/* Status field for pending extarnal dabt */
+uint8_t ext_dabt_pending;
/* State of our input IRQ/FIQ/VIRQ/VFIQ lines */
uint32_t irq_line_state;
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 5b82cefef6..10fe739c2d 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -37,6 +37,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
static bool cap_has_mp_state;
static bool cap_has_inject_serror_esr;
+static bool cap_has_inject_ext_dabt; /* KVM_CAP_ARM_INJECT_EXT_DABT */
static ARMHostCPUFeatures arm_host_cpu_features;
@@ -62,6 +63,12 @@ void kvm_arm_init_serror_injection(CPUState *cs)
KVM_CAP_ARM_INJECT_SERROR_ESR);
}
+void kvm_arm_init_ext_dabt_injection(CPUState *cs)
+{
+cap_has_inject_ext_dabt = kvm_check_extension(cs->kvm_state,
+KVM_CAP_ARM_INJECT_EXT_DABT);
+}
+
bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
int *fdarray,
struct kvm_vcpu_init *init)
@@ -218,6 +225,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
ret = -EINVAL;
}
+if (kvm_check_extension(s, KVM_CAP_ARM_NISV_TO_USER))
+if (kvm_vm_enable_cap(s, KVM_CAP_ARM_NISV_TO_USER, 0)) {
+warn_report("Failed to enable DABT NISV cap");
+}
+
return ret;
}
@@ -600,6 +612,10 @@ int kvm_put_vcpu_events(ARMCPU *cpu)
events.exception.serror_esr = env->serror.esr;
}
+if (cap_has_inject_ext_dabt) {
+events.exception.ext_dabt_pending = env->ext_dabt_pending;
+}
+
ret = kvm_vcpu_ioctl(CPU(cpu), KVM_SET_VCPU_EVENTS, &events);
if (ret) {
error_report("failed to put vcpu events");
@@ -629,6 +645,8 @@ int kvm_get_vcpu_events(ARMCPU *cpu)
env->serror.has_esr = events.exception.serror_has_esr;
env->serror.esr = events.exception.serror_esr;
+env->ext_dabt_pending = events.exception.ext_dabt_pending;
+
return 0;
}
@@ -701,6 +719,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
ret = EXCP_DEBUG;
} /* otherwise return to guest */
break;
+case KVM_EXIT_ARM_NISV:
+
