PowerPC kernel expects the number of SMT threads in a core to be a power of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel crash if invalid threads count is specified.
Prevent this crash and make it a graceful exit from QEMU itself by validating the user supplied threads count. Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> Acked-by: Stewart Smith <stew...@linux.vnet.ibm.com> --- Changes in v1: Make error message more descriptive as per Stewart's suggestion. v0: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00355.html target-ppc/translate_init.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c index 445c360..9ed22bb 100644 --- a/target-ppc/translate_init.c +++ b/target-ppc/translate_init.c @@ -18,6 +18,7 @@ * License along with this library; if not, see <http://www.gnu.org/licenses/>. */ +#include <math.h> #include "disas/bfd.h" #include "exec/gdbstub.h" #include <sysemu/kvm.h> @@ -7979,6 +7980,7 @@ static void ppc_cpu_realizefn(DeviceState *dev, Error **errp) Error *local_err = NULL; #if !defined(CONFIG_USER_ONLY) int max_smt = kvm_enabled() ? kvmppc_smt_threads() : 1; + int threads_shift; #endif #if !defined(CONFIG_USER_ONLY) @@ -7987,6 +7989,13 @@ static void ppc_cpu_realizefn(DeviceState *dev, Error **errp) max_smt, kvm_enabled() ? "KVM" : "TCG"); return; } + threads_shift = log2(smp_threads); + if (smp_threads != (1 << threads_shift)) { + error_setg(errp, "Cannot support %d threads on PPC with %s, " + "threads count must be a power of 2.", + smp_threads, kvm_enabled() ? "KVM" : "TCG"); + return; + } #endif if (kvm_enabled()) { -- 1.7.11.7
