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Re: [Qemu-ppc] [QEMU-PPC] [PATCH v3] powerpc/spapr: Add host threads par
From: |
Greg Kurz |
Subject: |
Re: [Qemu-ppc] [QEMU-PPC] [PATCH v3] powerpc/spapr: Add host threads parameter to ibm, get_system_parameter |
Date: |
Mon, 1 Jul 2019 11:01:40 +0200 |
On Mon, 1 Jul 2019 16:19:46 +1000
Suraj Jitindar Singh <address@hidden> wrote:
> The ibm,get_system_parameter rtas call is used by the guest to retrieve
> data relating to certain parameters of the system. The SPLPAR
> characteristics option (token 20) is used to determin characteristics of
> the environment in which the lpar will run.
>
> It may be useful for a guest to know the number of physical host threads
> present on the underlying system where it is being run. Add the
> characteristic "HostThrs" to the SPLPAR Characteristics
> ibm,get_system_parameter rtas call to expose this information to a
> guest and provide an implementation which determines this information
> based on the number of interrupt servers present in the device tree.
>
> Signed-off-by: Suraj Jitindar Singh <address@hidden>
>
> ---
Reviewed-by: Greg Kurz <address@hidden>
>
> V1 -> V2:
> - Take into account that the core may be operating in split core mode
> meaning a single core may be split into multiple subcores.
> V2 -> V3:
> - Add curly braces for single line if statements
> ---
> hw/ppc/spapr_rtas.c | 62
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 62 insertions(+)
>
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 5bc1a93271..1bab71c90c 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -229,6 +229,58 @@ static inline int sysparm_st(target_ulong addr,
> target_ulong len,
> return RTAS_OUT_SUCCESS;
> }
>
> +#define CPUS_PATH "/proc/device-tree/cpus/"
> +#define SUBCORE_PATH "/sys/devices/system/cpu/subcores_per_core"
> +
> +static int rtas_get_num_host_threads(void)
> +{
> + int num_threads = -1;
> + unsigned long len;
> + const char *entry;
> + char *buf;
> + GDir *dir;
> +
> + if (!kvm_enabled()) {
> + return 1;
> + }
> +
> + /* Read interrupt servers to determine number of threads per core */
> + dir = g_dir_open(CPUS_PATH, 0, NULL);
> + if (!dir) {
> + return -1;
> + }
> +
> + while ((entry = g_dir_read_name(dir))) {
> + if (!strncmp(entry, "PowerPC,POWER", strlen("PowerPC,POWER"))) {
> + char *path;
> +
> + path = g_strconcat(CPUS_PATH, entry,
> "/ibm,ppc-interrupt-server#s",
> + NULL);
> + if (g_file_get_contents(path, &buf, &len, NULL)) {
> + num_threads = len / sizeof(int);
> + g_free(buf);
> + }
> +
> + g_free(path);
> + break;
> + }
> + }
> +
> + g_dir_close(dir);
> +
> + /* Check if split core mode in use */
> + if (g_file_get_contents(SUBCORE_PATH, &buf, &len, NULL)) {
> + int subcores = g_ascii_strtoll(buf, NULL, 10);
> +
> + if (subcores) {
> + num_threads /= subcores;
> + }
> + g_free(buf);
> + }
> +
> + return num_threads;
> +}
> +
> static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu,
> SpaprMachineState *spapr,
> uint32_t token, uint32_t nargs,
> @@ -250,6 +302,16 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU
> *cpu,
> current_machine->ram_size / MiB,
> smp_cpus,
> max_cpus);
> + int num_host_threads = rtas_get_num_host_threads();
> +
> + if (num_host_threads > 0) {
> + char *hostthr_val, *old = param_val;
> +
> + hostthr_val = g_strdup_printf(",HostThrs=%d", num_host_threads);
> + param_val = g_strconcat(param_val, hostthr_val, NULL);
> + g_free(hostthr_val);
> + g_free(old);
> + }
> ret = sysparm_st(buffer, length, param_val, strlen(param_val) + 1);
> g_free(param_val);
> break;