Am 15.11.2013 um 00:12 schrieb Alexey Kardashevskiy <a...@ozlabs.ru>:
> At the moment only a whole CPU core can be assigned to a KVM. Since
> POWER7/8 support several threads per core, we want all threads of a core
> to go to the same KVM so every time we run QEMU with -enable-kvm on
> POWER, we have to add -smp X,threads=(4|8)" (4 for POWER7 and
> 8 for POWER8).
>
> This patch tries to read smp_threads number from an accelerator and
> falls back to the default value (1) if the accelerator did not care
> to change it.
>
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
>
> (!!!)
>
> The usual question - what would be the normal way of doing this?
> What does this patch break? I cannot think of anything right now.
Is this really what the user wants? On p7 you can run in no-smt, smt2 and smt4
mode. Today we simply default to no-smt. Changing defaults is usually a bad
thing.
Alex
>
>
> ---
> target-ppc/kvm.c | 6 ++++++
> vl.c | 29 ++++++++++++++++-------------
> 2 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 10d0cd9..80c0386 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -109,6 +109,12 @@ int kvm_arch_init(KVMState *s)
> "VM to stall at times!\n");
> }
>
> + if (!smp_threads) {
> + smp_threads = cap_ppc_smt;
> + } else {
> + smp_threads = MIN(smp_threads, cap_ppc_smt);
> + }
> +
> kvm_ppc_register_host_cpu_type();
>
> return 0;
> diff --git a/vl.c b/vl.c
> index 4ad15b8..97fa203 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -210,7 +210,7 @@ int singlestep = 0;
> int smp_cpus = 1;
> int max_cpus = 0;
> int smp_cores = 1;
> -int smp_threads = 1;
> +int smp_threads = 0;
> #ifdef CONFIG_VNC
> const char *vnc_display;
> #endif
> @@ -1395,7 +1395,9 @@ static void smp_parse(QemuOpts *opts)
> if (cpus == 0 || sockets == 0) {
> sockets = sockets > 0 ? sockets : 1;
> cores = cores > 0 ? cores : 1;
> - threads = threads > 0 ? threads : 1;
> + if (!threads) {
> + threads = smp_threads > 0 ? smp_threads : 1;
> + }
> if (cpus == 0) {
> cpus = cores * threads * sockets;
> }
> @@ -1413,7 +1415,8 @@ static void smp_parse(QemuOpts *opts)
> smp_cpus = cpus;
> smp_cores = cores > 0 ? cores : 1;
> smp_threads = threads > 0 ? threads : 1;
> -
> + } else if (!smp_threads) {
> + smp_threads = 1;
> }
>
> if (max_cpus == 0) {
> @@ -3880,16 +3883,6 @@ int main(int argc, char **argv, char **envp)
> data_dir[data_dir_idx++] = CONFIG_QEMU_DATADIR;
> }
>
> - smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
> -
> - machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */
> - if (smp_cpus > machine->max_cpus) {
> - fprintf(stderr, "Number of SMP cpus requested (%d), exceeds max cpus
> "
> - "supported by machine `%s' (%d)\n", smp_cpus, machine->name,
> - machine->max_cpus);
> - exit(1);
> - }
> -
> /*
> * Get the default machine options from the machine if it is not already
> * specified either by the configuration file or by the command line.
> @@ -4039,6 +4032,16 @@ int main(int argc, char **argv, char **envp)
>
> configure_accelerator();
>
> + smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
> +
> + machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */
> + if (smp_cpus > machine->max_cpus) {
> + fprintf(stderr, "Number of SMP cpus requested (%d), exceeds max cpus
> "
> + "supported by machine `%s' (%d)\n", smp_cpus, machine->name,
> + machine->max_cpus);
> + exit(1);
> + }
> +
> if (!qtest_enabled() && qtest_chrdev) {
> qtest_init();
> }
> --
> 1.8.4.rc4
>
>
