On 11/22/21 10:30, Peter Krempa wrote:
> On Fri, Nov 05, 2021 at 10:35:19 +0100, Michal Privoznik wrote:
>> It may come handy to be able to tweak TCG options, in this
>> specific case the size of translation block cache size (tb-size).
>> Since we can expect more knobs to tweak let's put them under
>> common element, like this:
>>
>> <domain>
>> <features>
>> <tcg>
>> <tb-cache unit='MiB'>128</tb-cache>
>> </tcg>
>> </features>
>> </domain>
>>
>> Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
>> Tested-by: Kashyap Chamarthy <kchamart@xxxxxxxxxx>
>> ---
>> docs/formatdomain.rst | 11 +++
>> docs/schemas/domaincommon.rng | 15 +++-
>> src/conf/domain_conf.c | 90 +++++++++++++++++++
>> src/conf/domain_conf.h | 7 ++
>> src/qemu/qemu_validate.c | 11 +++
>> .../x86_64-default-cpu-tcg-features.xml | 67 ++++++++++++++
>> ...default-cpu-tcg-features.x86_64-latest.xml | 1 +
>> tests/qemuxml2xmltest.c | 1 +
>> 8 files changed, 202 insertions(+), 1 deletion(-)
>> create mode 100644 tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.xml
>> create mode 120000 tests/qemuxml2xmloutdata/x86_64-default-cpu-tcg-features.x86_64-latest.xml
>
> [...]
>
>
>> @@ -21555,6 +21585,39 @@ virDomainRedirFilterDefCheckABIStability(virDomainRedirFilterDef *src,
>> }
>>
>>
>> +static bool
>> +virDomainFeatureTCGCheckABIStability(const virDomainDef *src,
>> + const virDomainDef *dst)
>> +{
>> + const int srcF = src->features[VIR_DOMAIN_FEATURE_TCG];
>> + const int dstF = dst->features[VIR_DOMAIN_FEATURE_TCG];
>> +
>> + if (srcF != dstF ||
>> + !!src->tcg_features != !!dst->tcg_features) {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> + _("State of feature '%s' differs: "
>> + "source: '%s', destination: '%s'"),
>> + virDomainFeatureTypeToString(VIR_DOMAIN_FEATURE_TCG),
>> + virTristateSwitchTypeToString(srcF),
>> + virTristateSwitchTypeToString(dstF));
>> + return false;
>> + }
>> +
>> + if (!src->tcg_features && !dst->tcg_features)
>> + return true;
>
> This check is either questionable (e.g. if just one of them is non-NULL,
> this doesn't trigger and the subsequent condition dereferences NULL in
> the other one), or unnecessary.
>
>> + if (src->tcg_features->tb_cache != dst->tcg_features->tb_cache) {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> + _("TCG tb-cache mismatch: source %llu, destination: %llu"),
>> + src->tcg_features->tb_cache,
>> + dst->tcg_features->tb_cache);
>
> I don't think this is ABI, do you have any supporting evidence? If yes,
> put it into the commnet for the next person questioning this.
Fair enough. I don't have any evidence. Let me remove the whole function.
>
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +
>> static bool
>> virDomainDefFeaturesCheckABIStability(virDomainDef *src,
>> virDomainDef *dst)
>
> [...]
>
>> @@ -27691,6 +27759,24 @@ virDomainDefFormatBlkiotune(virBuffer *buf,
>> }
>>
>>
>> +static void
>> +virDomainFeatureTCGFormat(virBuffer *buf,
>> + const virDomainDef *def)
>> +{
>> + g_auto(virBuffer) childBuf = VIR_BUFFER_INIT_CHILD(buf);
>> +
>> + if (!def->tcg_features ||
>> + def->features[VIR_DOMAIN_FEATURE_TCG] != VIR_TRISTATE_SWITCH_ON)
>> + return;
>> +
>> + virBufferAsprintf(&childBuf,
>> + "<tb-cache unit='KiB'>%lld</tb-cache>\n",
>> + def->tcg_features->tb_cache);
>
> This is not very extensible and similarly the parser as setting the
> cache to 0 is considered as not being present.
I'm not sure what you mean. If value 0 is passed then the parser won't
set def->features[VIR_DOMAIN_FEATURE_TCG] so this function exits early.
Do you want me to put if (val > 0) check here or something different?
>
>> +
>> + virXMLFormatElement(buf, "tcg", NULL, &childBuf);
>> +}
>> +
>> +
>> static int
>> virDomainDefFormatFeatures(virBuffer *buf,
>> virDomainDef *def)
>
> [...]
>
>> diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
>> index 397eea5ede..bd33c9a800 100644
>> --- a/src/qemu/qemu_validate.c
>> +++ b/src/qemu/qemu_validate.c
>> @@ -294,6 +294,17 @@ qemuValidateDomainDefFeatures(const virDomainDef *def,
>> }
>> break;
>>
>> + case VIR_DOMAIN_FEATURE_TCG:
>> + if (def->features[i] == VIR_TRISTATE_SWITCH_ON) {
>> + if (def->virtType != VIR_DOMAIN_VIRT_QEMU) {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> + _("TCG features are incompatible with domain type '%s'"),
>> + virDomainVirtTypeToString(def->virtType));
>> + return -1;
>> + }
>> + }
>> + break;
>> +
>
> Preferably, implement the qemu logic in the patch adding the qemu bits.
Fair enough. I thought that in this case it borderline okay, but I don't
care that much really.
Michal
