From b25ff3cd5a8b561f58b0245115d61cde0572cbdc Mon Sep 17 00:00:00 2001

From: David Gibson <dgibson@redhat.com>

Date: Fri, 19 Jan 2018 04:04:56 +0100

Subject: [PATCH 16/21] target/ppc: Clarify compat mode max_threads value

RH-Author: David Gibson <dgibson@redhat.com>

Message-id: <20180119040458.5629-3-dgibson@redhat.com>

Patchwork-id: 78676

O-Subject: [RHEL-7.5 qemu-kvm-rhev PATCH 2/4] target/ppc: Clarify compat mode max_threads value

Bugzilla: 1529243

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: David Gibson <david@gibson.dropbear.id.au>

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: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: Greg Kurz <groug@kaod.org>

Reviewed-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>

(cherry picked from commit abbc124753896f72e3715813ea20dd1924202ff0)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:

	hw/ppc/spapr.c

Contextual conflict.

Signed-off-by: David Gibson <dgibson@redhat.com>

---

 hw/ppc/spapr.c      |  4 ++--

 target/ppc/compat.c | 25 +++++++++++++++++--------

 target/ppc/cpu.h    |  2 +-

 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c

index 66227c3..5233366 100644

--- a/hw/ppc/spapr.c

+++ b/hw/ppc/spapr.c

@@ -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 = ppc_get_vcpu_dt_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;

@@ -506,7 +506,7 @@ 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];

diff --git a/target/ppc/compat.c b/target/ppc/compat.c

index 94ff14a..33658fb 100644

--- a/target/ppc/compat.c

+++ b/target/ppc/compat.c

@@ -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,

     },

 };

@@ -203,14 +212,14 @@ 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;

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h

index 6c770a2..9b107e4 100644

--- a/target/ppc/cpu.h

+++ b/target/ppc/cpu.h

@@ -1374,7 +1374,7 @@ 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);

-- 

1.8.3.1