Re: [PATCH v14 03/11] target/s390x/cpu topology: handle STSI(15) and build the SYSIB

[Pierre Morel]

On 1/16/23 14:11, Nina Schoetterl-Glausch wrote:
> On Thu, 2023-01-05 at 15:53 +0100, Pierre Morel wrote:
> > On interception of STSI(15.1.x) the System Information Block
> > (SYSIB) is built from the list of pre-ordered topology entries.
> >
> > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> > ---
> >   include/hw/s390x/cpu-topology.h |   3 +
> >   include/hw/s390x/sclp.h         |   1 +
> >   target/s390x/cpu.h              |  78 ++++++++++++++++++
> >   target/s390x/kvm/cpu_topology.c | 136 ++++++++++++++++++++++++++++++++
> >   target/s390x/kvm/kvm.c          |   5 +-
> >   target/s390x/kvm/meson.build    |   3 +-
> >   6 files changed, 224 insertions(+), 2 deletions(-)
> >   create mode 100644 target/s390x/kvm/cpu_topology.c
> >
> > diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
> > index b3fd752d8d..9571aa70e5 100644
> > --- a/include/hw/s390x/cpu-topology.h
> > +++ b/include/hw/s390x/cpu-topology.h
> > @@ -41,6 +41,9 @@ typedef union s390_topology_id {
> >       };
> >   } s390_topology_id;
> >   #define TOPO_CPU_MASK       0x000000000000003fUL
> > +#define TOPO_SOCKET_MASK    0x0000ffffff000000UL
> > +#define TOPO_BOOK_MASK      0x0000ffff00000000UL
> > +#define TOPO_DRAWER_MASK    0x0000ff0000000000UL
> >   
> >   typedef struct S390TopologyEntry {
> >       s390_topology_id id;
> > diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
> > index d3ade40a5a..712fd68123 100644
> > --- a/include/hw/s390x/sclp.h
> > +++ b/include/hw/s390x/sclp.h
> > @@ -112,6 +112,7 @@ typedef struct CPUEntry {
> >   } QEMU_PACKED CPUEntry;
> >   
> >   #define SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET     128
> > +#define SCLP_READ_SCP_INFO_MNEST                2
> >   typedef struct ReadInfo {
> >       SCCBHeader h;
> >       uint16_t rnmax;
> > diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> > index 39ea63a416..78988048dd 100644
> > --- a/target/s390x/cpu.h
> > +++ b/target/s390x/cpu.h
> > @@ -561,6 +561,25 @@ typedef struct SysIB_322 {
> >   } SysIB_322;
> >   QEMU_BUILD_BUG_ON(sizeof(SysIB_322) != 4096);
> >   
> > +#define S390_TOPOLOGY_MAG  6
> > +#define S390_TOPOLOGY_MAG6 0
> > +#define S390_TOPOLOGY_MAG5 1
> > +#define S390_TOPOLOGY_MAG4 2
> > +#define S390_TOPOLOGY_MAG3 3
> > +#define S390_TOPOLOGY_MAG2 4
> > +#define S390_TOPOLOGY_MAG1 5
> > +/* Configuration topology */
> > +typedef struct SysIB_151x {
> > +    uint8_t  reserved0[2];
> > +    uint16_t length;
> > +    uint8_t  mag[S390_TOPOLOGY_MAG];
> > +    uint8_t  reserved1;
> > +    uint8_t  mnest;
> > +    uint32_t reserved2;
> > +    char tle[];
> > +} QEMU_PACKED QEMU_ALIGNED(8) SysIB_151x;
> > +QEMU_BUILD_BUG_ON(sizeof(SysIB_151x) != 16);
> > +
> >   typedef union SysIB {
> >       SysIB_111 sysib_111;
> >       SysIB_121 sysib_121;
> > @@ -568,9 +587,68 @@ typedef union SysIB {
> >       SysIB_221 sysib_221;
> >       SysIB_222 sysib_222;
> >       SysIB_322 sysib_322;
> > +    SysIB_151x sysib_151x;
> >   } SysIB;
> >   QEMU_BUILD_BUG_ON(sizeof(SysIB) != 4096);
> >   
> > +/*
> > + * CPU Topology List provided by STSI with fc=15 provides a list
> > + * of two different Topology List Entries (TLE) types to specify
> > + * the topology hierarchy.
> > + *
> > + * - Container Topology List Entry
> > + *   Defines a container to contain other Topology List Entries
> > + *   of any type, nested containers or CPU.
> > + * - CPU Topology List Entry
> > + *   Specifies the CPUs position, type, entitlement and polarization
> > + *   of the CPUs contained in the last Container TLE.
> > + *
> > + * There can be theoretically up to five levels of containers, QEMU
> > + * uses only one level, the socket level.
> > + *
> > + * A container of with a nesting level (NL) greater than 1 can only
> > + * contain another container of nesting level NL-1.
> > + *
> > + * A container of nesting level 1 (socket), contains as many CPU TLE
> > + * as needed to describe the position and qualities of all CPUs inside
> > + * the container.
> > + * The qualities of a CPU are polarization, entitlement and type.
> > + *
> > + * The CPU TLE defines the position of the CPUs of identical qualities
> > + * using a 64bits mask which first bit has its offset defined by
> > + * the CPU address orgin field of the CPU TLE like in:
> > + * CPU address = origin * 64 + bit position within the mask
> > + *
> > + */
> > +/* Container type Topology List Entry */
> > +/* Container type Topology List Entry */
> > +typedef struct SysIBTl_container {
> > +        uint8_t nl;
> > +        uint8_t reserved[6];
> > +        uint8_t id;
> > +} QEMU_PACKED QEMU_ALIGNED(8) SysIBTl_container;
> > +QEMU_BUILD_BUG_ON(sizeof(SysIBTl_container) != 8);
> > +
> > +/* CPU type Topology List Entry */
> > +typedef struct SysIBTl_cpu {
> > +        uint8_t nl;
> > +        uint8_t reserved0[3];
> > +        uint8_t reserved1:5;
> > +        uint8_t dedicated:1;
> > +        uint8_t polarity:2;
> > +        uint8_t type;
> > +        uint16_t origin;
> > +        uint64_t mask;
> > +} QEMU_PACKED QEMU_ALIGNED(8) SysIBTl_cpu;
> > +QEMU_BUILD_BUG_ON(sizeof(SysIBTl_cpu) != 16);
> > +
> > +/* Max size of a SYSIB structure is when all CPU are alone in a container */
> > +#define S390_TOPOLOGY_SYSIB_SIZE (sizeof(SysIB_151x) +                         
> > \
> > +                                  S390_MAX_CPUS * (sizeof(SysIBTl_container) + 
> > \
> > +                                                   sizeof(SysIBTl_cpu)))
>
> I don't think this is accurate anymore, if you have drawers and books.
> In that case you could have 3 containers per 1 cpu.
> You could also use the maxcpus number at runtime instead of S390_MAX_CPUS.
> I also think you could do sizeof(SysIB) + sizeof(SysIBTl_cpu) if you check
> if the sysib overflows 4k while building it.

Right.
And I think your other proposal here under is better


> > +
> > +void insert_stsi_15_1_x(S390CPU *cpu, int sel2, __u64 addr, uint8_t ar);
> > +
> >   /* MMU defines */
> >   #define ASCE_ORIGIN           (~0xfffULL) /* segment table origin             
> > */
> >   #define ASCE_SUBSPACE         0x200       /* subspace group control           
> > */
> > diff --git a/target/s390x/kvm/cpu_topology.c b/target/s390x/kvm/cpu_topology.c
> > new file mode 100644
> > index 0000000000..3831a3264c
> > --- /dev/null
> > +++ b/target/s390x/kvm/cpu_topology.c
> > @@ -0,0 +1,136 @@
> > +/*
> > + * QEMU S390x CPU Topology
> > + *
> > + * Copyright IBM Corp. 2022
> > + * Author(s): Pierre Morel <pmorel@linux.ibm.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or (at
> > + * your option) any later version. See the COPYING file in the top-level
> > + * directory.
> > + */
> > +#include "qemu/osdep.h"
> > +#include "cpu.h"
> > +#include "hw/s390x/pv.h"
> > +#include "hw/sysbus.h"
> > +#include "hw/s390x/sclp.h"
> > +#include "hw/s390x/cpu-topology.h"
> > +
> > +static char *fill_container(char *p, int level, int id)
> > +{
> > +    SysIBTl_container *tle = (SysIBTl_container *)p;
> > +
> > +    tle->nl = level;
> > +    tle->id = id;
> > +    return p + sizeof(*tle);
> > +}
> > +
> > +static char *fill_tle_cpu(char *p, S390TopologyEntry *entry)
> > +{
> > +    SysIBTl_cpu *tle = (SysIBTl_cpu *)p;
> > +    s390_topology_id topology_id = entry->id;
> > +
> > +    tle->nl = 0;
> > +    tle->dedicated = topology_id.d;
> > +    tle->polarity = topology_id.p;
> > +    tle->type = topology_id.type;
> > +    tle->origin = topology_id.origin;
>
> You need to multiply that value by 64, no?
> And convert it to BE.

Yes right, I already had this error, I must have lost it in a rebase.


> > +    tle->mask = cpu_to_be64(entry->mask);
> > +    return p + sizeof(*tle);
> > +}
> > +
> > +static char *s390_top_set_level(char *p, int level)
> > +{
> > +    S390TopologyEntry *entry;
> > +    uint64_t last_socket = -1UL;
> > +    uint64_t last_book = -1UL;
> > +    uint64_t last_drawer = -1UL;
>
> -1UL looks funny to me, but there is nothing wrong with it.
> But I don't see a reason not to use int and initialize it with -1.
>
> > +    int drawer_cnt = 0;
> > +    int book_cnt = 0;
> > +    int socket_cnt = 0;
> > +
> > +    QTAILQ_FOREACH(entry, &s390_topology.list, next) {
> > +
> > +        if (level > 3 && (last_drawer != entry->id.drawer)) {
> > +            book_cnt = 0;
> > +            socket_cnt = 0;
> > +            p = fill_container(p, 3, drawer_cnt++);
> > +            last_drawer = entry->id.id & TOPO_DRAWER_MASK;
> > +            p = fill_container(p, 2, book_cnt++);
> > +            last_book = entry->id.id & TOPO_BOOK_MASK;
> > +            p = fill_container(p, 1, socket_cnt++);
> > +            last_socket = entry->id.id & TOPO_SOCKET_MASK;
> > +            p = fill_tle_cpu(p, entry);
> > +        } else if (level > 2 && (last_book !=
> > +                                 (entry->id.id & TOPO_BOOK_MASK))) {
> > +            socket_cnt = 0;
> > +            p = fill_container(p, 2, book_cnt++);
> > +            last_book = entry->id.id & TOPO_BOOK_MASK;
> > +            p = fill_container(p, 1, socket_cnt++);
> > +            last_socket = entry->id.id & TOPO_SOCKET_MASK;
> > +            p = fill_tle_cpu(p, entry);
> > +        } else if (last_socket != (entry->id.id & TOPO_SOCKET_MASK)) {
> > +            p = fill_container(p, 1, socket_cnt++);
> > +            last_socket = entry->id.id & TOPO_SOCKET_MASK;
> > +            p = fill_tle_cpu(p, entry);
> > +        } else {
> > +            p = fill_tle_cpu(p, entry);
> > +        }
> > +    }
> > +
> > +    return p;
> > +}
>
> I think you can do this a bit more readable and reduce redundancy.
> Pseudo code:
>
> foreach entry:
>         bool drawer_change = last_drawer != current_drawer
>         bool book_change = drawer_change || last_book != current_book
>         bool socket_change = book_change || last_socket != current_socket
>
>         if (level > 3 && drawer_change)
>                 reset book id
>                 fill drawer container
>                 drawer id++
>         if (level > 2 && book_change)
>                 reset socket id
>                 fill book container
>                 book id++
>         if (socket_change)
>                 fill socket container
>                 socket id++
>         fill cpu entry
>
>         update last_drawer, _book, _socket
>
> You can also check after after every fill if the buffer has been overflowed,
> that is if the function wrote more than sizeof(SysIB) - sizeof(SysIB_151x) 
> bytes.
> Or you check it once at the end if you increase the size of the buffer a bit.
> Then you don't need to allocate the absolute maximum.
>
> I think you could also use global ids for the containers.
> So directly use the drawer id from the entry,
> use (drawer id * smp.books) + book id, and so on.
> If you update last_* after setting *_changed you don't need to maintain ids,
> you can just use last_*.

OK, seems better to me
Thanks

Regards,
Pierre


> [...]

--
Pierre Morel
IBM Lab Boeblingen