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 <[email protected]>
>> ---
>> 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
>>
>>
>
