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@redhat.com> --- 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 -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|