On Fri, Jan 15, 2010 at 04:58:59PM +0100, Jiri Denemark wrote:
> Current implementation of x86Decode() used for CPUID -> model+features
> translation does not always select the closest CPU model. When walking
> through all models from cpu_map.xml the function considers a new
> candidate as a better choice than a previously selected candidate only
> if the new one is a superset of the old one. In case the new candidate
> is closer to host CPU but lacks some feature comparing to the old
> candidate, the function does not choose well.
>
> This patch changes the algorithm so that the closest model is always
> selected. That is, the model which requires the lowest number of
> additional features to describe host CPU.
>
> Signed-off-by: Jiri Denemark <jdenemar@xxxxxxxxxx>
> ---
> src/cpu/cpu_x86.c | 122 ++++++++++++++++++++++++++++++++++-------------------
> 1 files changed, 78 insertions(+), 44 deletions(-)
>
> diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
> index 298b632..dae7c90 100644
> --- a/src/cpu/cpu_x86.c
> +++ b/src/cpu/cpu_x86.c
> @@ -238,6 +238,55 @@ x86DataFromModel(const struct x86_model *model)
> }
>
>
> +static virCPUDefPtr
> +x86DataToCPU(const union cpuData *data,
> + const struct x86_model *model,
> + const struct x86_map *map)
> +{
> + virCPUDefPtr cpu;
> + union cpuData *tmp = NULL;
> + struct cpuX86cpuid *cpuid;
> + const struct x86_feature *feature;
> + int i;
> +
> + if (VIR_ALLOC(cpu) < 0 ||
> + (cpu->model = strdup(model->name)) == NULL ||
> + (tmp = x86DataCopy(data)) == NULL)
> + goto no_memory;
> +
> + for (i = 0; i < model->ncpuid; i++) {
> + x86cpuidClearBits(x86DataCpuid(tmp, model->cpuid[i].function),
> + model->cpuid + i);
> + }
> +
> + feature = map->features;
> + while (feature != NULL) {
> + for (i = 0; i < feature->ncpuid; i++) {
> + if ((cpuid = x86DataCpuid(tmp, feature->cpuid[i].function))
> + && x86cpuidMatchMasked(cpuid, feature->cpuid + i)) {
> + x86cpuidClearBits(cpuid, feature->cpuid + i);
> + if (virCPUDefAddFeature(NULL, cpu, feature->name,
> + VIR_CPU_FEATURE_REQUIRE) < 0)
> + goto error;
> + }
> + }
> +
> + feature = feature->next;
> + }
> +
> +cleanup:
> + x86DataFree(tmp);
> + return cpu;
> +
> +no_memory:
> + virReportOOMError(NULL);
> +error:
> + virCPUDefFree(cpu);
> + cpu = NULL;
> + goto cleanup;
> +}
> +
> +
> static void
> x86FeatureFree(struct x86_feature *feature)
> {
> @@ -896,10 +945,9 @@ x86Decode(virCPUDefPtr cpu,
> {
> int ret = -1;
> struct x86_map *map;
> - const struct x86_feature *feature;
> - const struct x86_model *model = NULL;
> const struct x86_model *candidate;
> - union cpuData *tmp = NULL;
> + virCPUDefPtr cpuCandidate;
> + virCPUDefPtr cpuModel = NULL;
> struct cpuX86cpuid *cpuid;
> int i;
>
> @@ -908,6 +956,8 @@ x86Decode(virCPUDefPtr cpu,
>
> candidate = map->models;
> while (candidate != NULL) {
> + bool allowed = (models == NULL);
> +
> for (i = 0; i < candidate->ncpuid; i++) {
> cpuid = x86DataCpuid(data, candidate->cpuid[i].function);
> if (cpuid == NULL
> @@ -915,65 +965,49 @@ x86Decode(virCPUDefPtr cpu,
> goto next;
> }
>
> - if (model == NULL
> - || x86ModelCompare(model, candidate) == SUBSET) {
> - bool found = false;
> - for (i = 0; i < nmodels; i++) {
> - if (STREQ(models[i], candidate->name)) {
> - found = true;
> - break;
> - }
> + for (i = 0; i < nmodels; i++) {
> + if (STREQ(models[i], candidate->name)) {
> + allowed = true;
> + break;
> }
> + }
>
> - if (nmodels > 0 && !found) {
> - VIR_DEBUG("CPU model %s not allowed by hypervisor; ignoring",
> - candidate->name);
> - }
> - else
> - model = candidate;
> + if (!allowed) {
> + VIR_DEBUG("CPU model %s not allowed by hypervisor; ignoring",
> + candidate->name);
> + goto next;
> }
>
> + if (!(cpuCandidate = x86DataToCPU(data, candidate, map)))
> + goto out;
> +
> + if (cpuModel == NULL
> + || cpuModel->nfeatures > cpuCandidate->nfeatures) {
> + virCPUDefFree(cpuModel);
> + cpuModel = cpuCandidate;
> + } else
> + virCPUDefFree(cpuCandidate);
> +
> next:
> candidate = candidate->next;
> }
>
> - if (model == NULL) {
> + if (cpuModel == NULL) {
> virCPUReportError(NULL, VIR_ERR_INTERNAL_ERROR,
> "%s", _("Cannot find suitable CPU model for given data"));
> goto out;
> }
>
> - if ((cpu->model = strdup(model->name)) == NULL
> - || (tmp = x86DataCopy(data)) == NULL) {
> - virReportOOMError(NULL);
> - goto out;
> - }
> -
> - for (i = 0; i < model->ncpuid; i++) {
> - x86cpuidClearBits(x86DataCpuid(tmp, model->cpuid[i].function),
> - model->cpuid + i);
> - }
> -
> - feature = map->features;
> - while (feature != NULL) {
> - for (i = 0; i < feature->ncpuid; i++) {
> - if ((cpuid = x86DataCpuid(tmp, feature->cpuid[i].function))
> - && x86cpuidMatchMasked(cpuid, feature->cpuid + i)) {
> - x86cpuidClearBits(cpuid, feature->cpuid + i);
> - if (virCPUDefAddFeature(NULL, cpu, feature->name,
> - VIR_CPU_FEATURE_REQUIRE) < 0)
> - goto out;
> - }
> - }
> -
> - feature = feature->next;
> - }
> + cpu->model = cpuModel->model;
> + cpu->nfeatures = cpuModel->nfeatures;
> + cpu->features = cpuModel->features;
> + VIR_FREE(cpuModel);
>
> ret = 0;
>
> out:
> - x86DataFree(tmp);
> x86MapFree(map);
> + virCPUDefFree(cpuModel);
>
> return ret;
> }
> --
ACK
Daniel
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