Commit abbc1247 authored by David Gibson's avatar David Gibson
Browse files

target/ppc: Clarify compat mode max_threads value 



We recently had some discussions that were sidetracked for a while, because
nearly everyone misapprehended the purpose of the 'max_threads' field in
the compatiblity modes table.  It's all about guest expectations, not host
expectations or support (that's handled elsewhere).

In an attempt to avoid a repeat of that confusion, rename the field to
'max_vthreads' and add an explanatory comment.

Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Reviewed-by: default avatarLaurent Vivier <lvivier@redhat.com>
Reviewed-by: default avatarGreg Kurz <groug@kaod.org>
Reviewed-by: default avatarJose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
parent 03ee51d3

hw/ppc/spapr.c

+2 −2
Original line number Diff line number Diff line
@@ -345,7 +345,7 @@ static int spapr_fixup_cpu_dt(void *fdt, sPAPRMachineState *spapr) 
        PowerPCCPU *cpu = POWERPC_CPU(cs);

        DeviceClass *dc = DEVICE_GET_CLASS(cs);

        int index = spapr_vcpu_id(cpu);

        int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));

        int compat_smt = MIN(smp_threads, ppc_compat_max_vthreads(cpu));



        if ((index % smt) != 0) {

            continue;
@@ -503,7 +503,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset, 
    size_t page_sizes_prop_size;

    uint32_t vcpus_per_socket = smp_threads * smp_cores;

    uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};

    int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));

    int compat_smt = MIN(smp_threads, ppc_compat_max_vthreads(cpu));

    sPAPRDRConnector *drc;

    int drc_index;

    uint32_t radix_AP_encodings[PPC_PAGE_SIZES_MAX_SZ];

target/ppc/compat.c

+17 −8
Original line number Diff line number Diff line
@@ -32,7 +32,16 @@ typedef struct { 
    uint32_t pvr;

    uint64_t pcr;

    uint64_t pcr_level;

    int max_threads;



    /*

     * Maximum allowed virtual threads per virtual core

     *

     * This is to stop older guests getting confused by seeing more

     * threads than they think the cpu can support.  Usually it's

     * equal to the number of threads supported on bare metal

     * hardware, but not always (see POWER9).

     */

    int max_vthreads;

} CompatInfo;



static const CompatInfo compat_table[] = {
@@ -45,28 +54,28 @@ static const CompatInfo compat_table[] = { 
        .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 |

               PCR_COMPAT_2_05 | PCR_TM_DIS | PCR_VSX_DIS,

        .pcr_level = PCR_COMPAT_2_05,

        .max_threads = 2,

        .max_vthreads = 2,

    },

    { /* POWER7, ISA2.06 */

        .name = "power7",

        .pvr = CPU_POWERPC_LOGICAL_2_06,

        .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,

        .pcr_level = PCR_COMPAT_2_06,

        .max_threads = 4,

        .max_vthreads = 4,

    },

    {

        .name = "power7+",

        .pvr = CPU_POWERPC_LOGICAL_2_06_PLUS,

        .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,

        .pcr_level = PCR_COMPAT_2_06,

        .max_threads = 4,

        .max_vthreads = 4,

    },

    { /* POWER8, ISA2.07 */

        .name = "power8",

        .pvr = CPU_POWERPC_LOGICAL_2_07,

        .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07,

        .pcr_level = PCR_COMPAT_2_07,

        .max_threads = 8,

        .max_vthreads = 8,

    },

    { /* POWER9, ISA3.00 */

        .name = "power9",
@@ -80,7 +89,7 @@ static const CompatInfo compat_table[] = { 
         * confusing if half of the threads disappear from the guest

         * if it announces it's POWER9 aware at CAS time.

         */

        .max_threads = 8,

        .max_vthreads = 8,

    },

};
@@ -192,14 +201,14 @@ void ppc_set_compat_all(uint32_t compat_pvr, Error **errp) 
    }

}



int ppc_compat_max_threads(PowerPCCPU *cpu)

int ppc_compat_max_vthreads(PowerPCCPU *cpu)

{

    const CompatInfo *compat = compat_by_pvr(cpu->compat_pvr);

    int n_threads = CPU(cpu)->nr_threads;



    if (cpu->compat_pvr) {

        g_assert(compat);

        n_threads = MIN(n_threads, compat->max_threads);

        n_threads = MIN(n_threads, compat->max_vthreads);

    }



    return n_threads;

target/ppc/cpu.h

+1 −1
Original line number Diff line number Diff line
@@ -1395,7 +1395,7 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr, Error **errp); 
#if !defined(CONFIG_USER_ONLY)

void ppc_set_compat_all(uint32_t compat_pvr, Error **errp);

#endif

int ppc_compat_max_threads(PowerPCCPU *cpu);

int ppc_compat_max_vthreads(PowerPCCPU *cpu);

void ppc_compat_add_property(Object *obj, const char *name,

                             uint32_t *compat_pvr, const char *basedesc,

                             Error **errp);