If there is a mismatch between the cpreg indexes found on both ends,
check whether a tolerance was registered for the given kvmidx. If any,
silence warning/errors.
Create dedicated helper functions that print the name of the culprit reg
and analyze whether a tolerance is set. According set the level of traces
and analyze whether the migration must eventually fail.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
target/arm/machine.c | 30 ++++++++++++++++++++----------
target/arm/trace-events | 2 ++
2 files changed, 22 insertions(+), 10 deletions(-)
diff --git a/target/arm/machine.c b/target/arm/machine.c
index 476dad00ee7..13b8a0b2220 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -1065,24 +1065,34 @@ static void handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx
{
g_autofree gchar *name = print_register_name(kvmidx);
- warn_report("%s: %s "
- "expected by the destination but not in the incoming stream: "
- "skip it", __func__, name);
+ if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
+ 0, 0, ToleranceNotOnBothEnds)) {
+ warn_report("%s: %s "
+ "expected by the destination but not in the incoming stream: "
+ "skip it", __func__, name);
+ } else {
+ trace_tolerate_cpreg_missing_in_incoming_stream(name);
+ }
}
/*
- * Handle the situation where @kvmidx is in the incoming stream
- * but not on destination. This currently fails the migration but
- * we plan to accomodate some exceptions, hence the boolean returned value.
+ * Handle the situation where @kvmidx is in the incoming
+ * stream but not on destination. This fails the migration if
+ * no cpreg mig tolerance is set for this @kvmidx
*/
static bool handle_cpreg_only_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx)
{
g_autofree gchar *name = print_register_name(kvmidx);
- bool fail = true;
-
- error_report("%s: %s in the incoming stream but unknown on the "
- "destination: fail migration", __func__, name);
+ bool fail = false;
+ if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
+ 0, 0, ToleranceNotOnBothEnds)) {
+ error_report("%s: %s in the incoming stream but unknown on the "
+ "destination: fail migration", __func__, name);
+ fail = true;
+ } else {
+ trace_tolerate_cpreg_only_in_incoming_stream(name);
+ }
return fail;
}
diff --git a/target/arm/trace-events b/target/arm/trace-events
index 2de0406f784..8502fb3265c 100644
--- a/target/arm/trace-events
+++ b/target/arm/trace-events
@@ -29,3 +29,5 @@ arm_psci_call(uint64_t x0, uint64_t x1, uint64_t x2, uint64_t x3, uint32_t cpuid
# machine.c
cpu_post_load(uint32_t cpreg_vmstate_array_len, uint32_t cpreg_array_len) "cpreg_vmstate_array_len=%d cpreg_array_len=%d"
+tolerate_cpreg_missing_in_incoming_stream(char *name) "%s is missing in incoming stream but this is explicitly tolerated"
+tolerate_cpreg_only_in_incoming_stream(char *name) "%s is in incoming stream but not on destination but this is explicitly tolerated"
--
2.53.0On Wed, 4 Mar 2026, Eric Auger wrote:
> If there is a mismatch between the cpreg indexes found on both ends,
> check whether a tolerance was registered for the given kvmidx. If any,
> silence warning/errors.
>
> Create dedicated helper functions that print the name of the culprit reg
> and analyze whether a tolerance is set. According set the level of traces
> and analyze whether the migration must eventually fail.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
> target/arm/machine.c | 30 ++++++++++++++++++++----------
> target/arm/trace-events | 2 ++
> 2 files changed, 22 insertions(+), 10 deletions(-)
>
> diff --git a/target/arm/machine.c b/target/arm/machine.c
> index 476dad00ee7..13b8a0b2220 100644
> --- a/target/arm/machine.c
> +++ b/target/arm/machine.c
> @@ -1065,24 +1065,34 @@ static void handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx
> {
> g_autofree gchar *name = print_register_name(kvmidx);
>
> - warn_report("%s: %s "
> - "expected by the destination but not in the incoming stream: "
> - "skip it", __func__, name);
> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
> + 0, 0, ToleranceNotOnBothEnds)) {
I don't get this. You apply a different tolerance type than the one
(potentially) registered. This check will only fail when there was no
tolerance registered for this kvmidx. But this can be changed by someone
registering a different type.
> + warn_report("%s: %s "
> + "expected by the destination but not in the incoming stream: "
> + "skip it", __func__, name);
> + } else {
> + trace_tolerate_cpreg_missing_in_incoming_stream(name);
> + }
> }
>
> /*
> - * Handle the situation where @kvmidx is in the incoming stream
> - * but not on destination. This currently fails the migration but
> - * we plan to accomodate some exceptions, hence the boolean returned value.
> + * Handle the situation where @kvmidx is in the incoming
> + * stream but not on destination. This fails the migration if
> + * no cpreg mig tolerance is set for this @kvmidx
> */
> static bool handle_cpreg_only_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx)
> {
> g_autofree gchar *name = print_register_name(kvmidx);
> - bool fail = true;
> -
> - error_report("%s: %s in the incoming stream but unknown on the "
> - "destination: fail migration", __func__, name);
> + bool fail = false;
>
> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
> + 0, 0, ToleranceNotOnBothEnds)) {
> + error_report("%s: %s in the incoming stream but unknown on the "
> + "destination: fail migration", __func__, name);
> + fail = true;
> + } else {
> + trace_tolerate_cpreg_only_in_incoming_stream(name);
> + }
> return fail;
> }
>
> diff --git a/target/arm/trace-events b/target/arm/trace-events
> index 2de0406f784..8502fb3265c 100644
> --- a/target/arm/trace-events
> +++ b/target/arm/trace-events
> @@ -29,3 +29,5 @@ arm_psci_call(uint64_t x0, uint64_t x1, uint64_t x2, uint64_t x3, uint32_t cpuid
>
> # machine.c
> cpu_post_load(uint32_t cpreg_vmstate_array_len, uint32_t cpreg_array_len) "cpreg_vmstate_array_len=%d cpreg_array_len=%d"
> +tolerate_cpreg_missing_in_incoming_stream(char *name) "%s is missing in incoming stream but this is explicitly tolerated"
> +tolerate_cpreg_only_in_incoming_stream(char *name) "%s is in incoming stream but not on destination but this is explicitly tolerated"
> --
> 2.53.0
>
>
On 3/6/26 11:51 AM, Sebastian Ott wrote:
> On Wed, 4 Mar 2026, Eric Auger wrote:
>> If there is a mismatch between the cpreg indexes found on both ends,
>> check whether a tolerance was registered for the given kvmidx. If any,
>> silence warning/errors.
>>
>> Create dedicated helper functions that print the name of the culprit reg
>> and analyze whether a tolerance is set. According set the level of
>> traces
>> and analyze whether the migration must eventually fail.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>> target/arm/machine.c | 30 ++++++++++++++++++++----------
>> target/arm/trace-events | 2 ++
>> 2 files changed, 22 insertions(+), 10 deletions(-)
>>
>> diff --git a/target/arm/machine.c b/target/arm/machine.c
>> index 476dad00ee7..13b8a0b2220 100644
>> --- a/target/arm/machine.c
>> +++ b/target/arm/machine.c
>> @@ -1065,24 +1065,34 @@ static void
>> handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx
>> {
>> g_autofree gchar *name = print_register_name(kvmidx);
>>
>> - warn_report("%s: %s "
>> - "expected by the destination but not in the incoming
>> stream: "
>> - "skip it", __func__, name);
>> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
>> + 0, 0,
>> ToleranceNotOnBothEnds)) {
>
> I don't get this. You apply a different tolerance type than the one
> (potentially) registered. This check will only fail when there was no
> tolerance registered for this kvmidx. But this can be changed by someone
> registering a different type.
Note at the moment, only one tolerance can be registered for a kvmidx
Eric
>
>> + warn_report("%s: %s "
>> + "expected by the destination but not in the
>> incoming stream: "
>> + "skip it", __func__, name);
>> + } else {
>> + trace_tolerate_cpreg_missing_in_incoming_stream(name);
>> + }
>> }
>>
>> /*
>> - * Handle the situation where @kvmidx is in the incoming stream
>> - * but not on destination. This currently fails the migration but
>> - * we plan to accomodate some exceptions, hence the boolean returned
>> value.
>> + * Handle the situation where @kvmidx is in the incoming
>> + * stream but not on destination. This fails the migration if
>> + * no cpreg mig tolerance is set for this @kvmidx
>> */
>> static bool handle_cpreg_only_in_incoming_stream(ARMCPU *cpu,
>> uint64_t kvmidx)
>> {
>> g_autofree gchar *name = print_register_name(kvmidx);
>> - bool fail = true;
>> -
>> - error_report("%s: %s in the incoming stream but unknown on the "
>> - "destination: fail migration", __func__, name);
>> + bool fail = false;
>>
>> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
>> + 0, 0,
>> ToleranceNotOnBothEnds)) {
>> + error_report("%s: %s in the incoming stream but unknown on
>> the "
>> + "destination: fail migration", __func__, name);
>> + fail = true;
>> + } else {
>> + trace_tolerate_cpreg_only_in_incoming_stream(name);
>> + }
>> return fail;
>> }
>>
>> diff --git a/target/arm/trace-events b/target/arm/trace-events
>> index 2de0406f784..8502fb3265c 100644
>> --- a/target/arm/trace-events
>> +++ b/target/arm/trace-events
>> @@ -29,3 +29,5 @@ arm_psci_call(uint64_t x0, uint64_t x1, uint64_t
>> x2, uint64_t x3, uint32_t cpuid
>>
>> # machine.c
>> cpu_post_load(uint32_t cpreg_vmstate_array_len, uint32_t
>> cpreg_array_len) "cpreg_vmstate_array_len=%d cpreg_array_len=%d"
>> +tolerate_cpreg_missing_in_incoming_stream(char *name) "%s is missing
>> in incoming stream but this is explicitly tolerated"
>> +tolerate_cpreg_only_in_incoming_stream(char *name) "%s is in
>> incoming stream but not on destination but this is explicitly tolerated"
>> --
>> 2.53.0
>>
>>
>
On 3/6/26 11:51 AM, Sebastian Ott wrote:
> On Wed, 4 Mar 2026, Eric Auger wrote:
>> If there is a mismatch between the cpreg indexes found on both ends,
>> check whether a tolerance was registered for the given kvmidx. If any,
>> silence warning/errors.
>>
>> Create dedicated helper functions that print the name of the culprit reg
>> and analyze whether a tolerance is set. According set the level of
>> traces
>> and analyze whether the migration must eventually fail.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>> target/arm/machine.c | 30 ++++++++++++++++++++----------
>> target/arm/trace-events | 2 ++
>> 2 files changed, 22 insertions(+), 10 deletions(-)
>>
>> diff --git a/target/arm/machine.c b/target/arm/machine.c
>> index 476dad00ee7..13b8a0b2220 100644
>> --- a/target/arm/machine.c
>> +++ b/target/arm/machine.c
>> @@ -1065,24 +1065,34 @@ static void
>> handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx
>> {
>> g_autofree gchar *name = print_register_name(kvmidx);
>>
>> - warn_report("%s: %s "
>> - "expected by the destination but not in the incoming
>> stream: "
>> - "skip it", __func__, name);
>> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
>> + 0, 0,
>> ToleranceNotOnBothEnds)) {
>
> I don't get this. You apply a different tolerance type than the one
> (potentially) registered. This check will only fail when there was no
> tolerance registered for this kvmidx. But this can be changed by someone
> registering a different type.
OK so we know the cpreg is missing in the input stream. If there is a
tolerance of type ToleranceNotOnBothEnds for this kvmidx, that's fine,
we just trace and do not report any warning. Otherwise we warn_report
the issue but do not fail.
Does it clarify?
Eric
>
>> + warn_report("%s: %s "
>> + "expected by the destination but not in the
>> incoming stream: "
>> + "skip it", __func__, name);
>> + } else {
>> + trace_tolerate_cpreg_missing_in_incoming_stream(name);
>> + }
>> }
>>
>> /*
>> - * Handle the situation where @kvmidx is in the incoming stream
>> - * but not on destination. This currently fails the migration but
>> - * we plan to accomodate some exceptions, hence the boolean returned
>> value.
>> + * Handle the situation where @kvmidx is in the incoming
>> + * stream but not on destination. This fails the migration if
>> + * no cpreg mig tolerance is set for this @kvmidx
>> */
>> static bool handle_cpreg_only_in_incoming_stream(ARMCPU *cpu,
>> uint64_t kvmidx)
>> {
>> g_autofree gchar *name = print_register_name(kvmidx);
>> - bool fail = true;
>> -
>> - error_report("%s: %s in the incoming stream but unknown on the "
>> - "destination: fail migration", __func__, name);
>> + bool fail = false;
>>
>> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
>> + 0, 0,
>> ToleranceNotOnBothEnds)) {
>> + error_report("%s: %s in the incoming stream but unknown on
>> the "
>> + "destination: fail migration", __func__, name);
>> + fail = true;
>> + } else {
>> + trace_tolerate_cpreg_only_in_incoming_stream(name);
>> + }
>> return fail;
>> }
>>
>> diff --git a/target/arm/trace-events b/target/arm/trace-events
>> index 2de0406f784..8502fb3265c 100644
>> --- a/target/arm/trace-events
>> +++ b/target/arm/trace-events
>> @@ -29,3 +29,5 @@ arm_psci_call(uint64_t x0, uint64_t x1, uint64_t
>> x2, uint64_t x3, uint32_t cpuid
>>
>> # machine.c
>> cpu_post_load(uint32_t cpreg_vmstate_array_len, uint32_t
>> cpreg_array_len) "cpreg_vmstate_array_len=%d cpreg_array_len=%d"
>> +tolerate_cpreg_missing_in_incoming_stream(char *name) "%s is missing
>> in incoming stream but this is explicitly tolerated"
>> +tolerate_cpreg_only_in_incoming_stream(char *name) "%s is in
>> incoming stream but not on destination but this is explicitly tolerated"
>> --
>> 2.53.0
>>
>>
>
On Fri, 6 Mar 2026, Eric Auger wrote:
> On 3/6/26 11:51 AM, Sebastian Ott wrote:
>> On Wed, 4 Mar 2026, Eric Auger wrote:
>>> If there is a mismatch between the cpreg indexes found on both ends,
>>> check whether a tolerance was registered for the given kvmidx. If any,
>>> silence warning/errors.
>>>
>>> Create dedicated helper functions that print the name of the culprit reg
>>> and analyze whether a tolerance is set. According set the level of
>>> traces
>>> and analyze whether the migration must eventually fail.
>>>
>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>> ---
>>> target/arm/machine.c | 30 ++++++++++++++++++++----------
>>> target/arm/trace-events | 2 ++
>>> 2 files changed, 22 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/target/arm/machine.c b/target/arm/machine.c
>>> index 476dad00ee7..13b8a0b2220 100644
>>> --- a/target/arm/machine.c
>>> +++ b/target/arm/machine.c
>>> @@ -1065,24 +1065,34 @@ static void
>>> handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx
>>> {
>>> g_autofree gchar *name = print_register_name(kvmidx);
>>>
>>> - warn_report("%s: %s "
>>> - "expected by the destination but not in the incoming
>>> stream: "
>>> - "skip it", __func__, name);
>>> + if (!arm_cpu_cpreg_has_mig_tolerance(cpu, kvmidx,
>>> + 0, 0,
>>> ToleranceNotOnBothEnds)) {
>>
>> I don't get this. You apply a different tolerance type than the one
>> (potentially) registered. This check will only fail when there was no
>> tolerance registered for this kvmidx. But this can be changed by someone
>> registering a different type.
>
> OK so we know the cpreg is missing in the input stream. If there is a
> tolerance of type ToleranceNotOnBothEnds for this kvmidx, that's fine,
> we just trace and do not report any warning. Otherwise we warn_report
> the issue but do not fail.
> Does it clarify?
Yes, it does.
It just feels a bit odd that we identify specific issues when comparing
destination vs incomming stream and then test if that specific issue is
tolerated. With the infrastructure from patch 1 I would have expected
that arm_cpu_cpreg_has_mig_tolerance() can already handle the specific
issues - something like:
if (dest[i] == incomming[i]) {
//all good
} else if (arm_cpu_cpreg_has_mig_tolerance()) {
//all good
} else
fail();
..but I guess I'm just missing smth.
Sebastian
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