Re: [Qemu-devel] [PATCH v4] spapr: add uuid/host details to device tree

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

Alexander Graf <agraf@suse.de> writes:

> On 08.07.14 07:00, Nikunj A Dadhania wrote:
>> Useful for identifying the guest/host uniquely within the
>> guest. Adding following properties to the guest root node.
>>
>> vm,uuid - uuid of the guest
>> host-model - Host model number
>> host-serial - Host machine serial number
>> hypervisor type - Tells its "kvm"
>>
>> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
>>
>> ---
>> v4: make uuid as human readable
>> v3: rebase to ppcnext
>> v2: indentation fixes
>> ---
>>   hw/ppc/spapr.c       | 25 +++++++++++++++++++++++++
>>   target-ppc/kvm.c     | 44 +++++++++++++++++++++++++++++++++++++++++++-
>>   target-ppc/kvm_ppc.h | 12 ++++++++++++
>>   3 files changed, 80 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index 077ad2d..485ea66 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -318,6 +318,7 @@ static void *spapr_create_fdt_skel(hwaddr initrd_base,
>>       QemuOpts *opts = qemu_opts_find(qemu_find_opts("smp-opts"), NULL);
>>       unsigned sockets = opts ? qemu_opt_get_number(opts, "sockets", 0) : 0;
>>       uint32_t cpus_per_socket = sockets ? (smp_cpus / sockets) : 1;
>> +    char char_buf[512];
>
> Can't you just return callee allocated, caller free'd memory?

Tried doing it more in line of read_cpuinfo in target-ppc/kvm.c
I could do it either ways.

>
>>   
>>       add_str(hypertas, "hcall-pft");
>>       add_str(hypertas, "hcall-term");
>> @@ -347,6 +348,30 @@ static void *spapr_create_fdt_skel(hwaddr initrd_base,
>>       _FDT((fdt_property_string(fdt, "model", "IBM pSeries (emulated by qemu)")));
>>       _FDT((fdt_property_string(fdt, "compatible", "qemu,pseries")));
>>   
>> +    if (kvm_enabled()) {
>> +        _FDT((fdt_property_string(fdt, "hypervisor", "kvm")));
>> +    }
>> +
>> +    /*
>> +     * Add info to guest to indentify which host is it being run on
>> +     * and what is the uuid of the guest
>> +     */
>> +    memset(char_buf, 0, sizeof(char_buf));
>> +    if (!kvmppc_get_host_model(char_buf, sizeof(char_buf))) {
>> +        _FDT((fdt_property_string(fdt, "host-model", char_buf)));
>> +        memset(char_buf, 0, sizeof(char_buf));
>> +    }
>> +    if (!kvmppc_get_host_serial(char_buf, sizeof(char_buf))) {
>> +        _FDT((fdt_property_string(fdt, "host-serial", char_buf)));
>> +    }
>
> Please be aware that all of the above is bogus when you start thinking 
> about live migration.

Yes, there are tools that look at these. Is there a way to update these
on migration?

>
>> +
>> +    snprintf(char_buf, 37, UUID_FMT, qemu_uuid[0], qemu_uuid[1],
>
> g_strdup_printf()

Ok.

>
>> +             qemu_uuid[2], qemu_uuid[3], qemu_uuid[4], qemu_uuid[5],
>> +             qemu_uuid[6], qemu_uuid[7], qemu_uuid[8], qemu_uuid[9],
>> +             qemu_uuid[10], qemu_uuid[11], qemu_uuid[12], qemu_uuid[13],
>> +             qemu_uuid[14], qemu_uuid[15]);
>> +    _FDT((fdt_property_string(fdt, "vm,uuid", char_buf)));
>> +
>>       _FDT((fdt_property_cell(fdt, "#address-cells", 0x2)));
>>       _FDT((fdt_property_cell(fdt, "#size-cells", 0x2)));
>>   
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 2d87108..25091f8 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -1369,7 +1369,7 @@ static int read_cpuinfo(const char *field, char *value, int len)
>>       }
>>   
>>       do {
>> -        if(!fgets(line, sizeof(line), f)) {
>> +        if (!fgets(line, sizeof(line), f)) {
>>               break;
>>           }
>>           if (!strncmp(line, field, field_len)) {
>> @@ -1404,6 +1404,48 @@ uint32_t kvmppc_get_tbfreq(void)
>>       return retval;
>>   }
>>   
>> +int32_t kvmppc_get_host_serial(char *value, int len)
>> +{
>> +    FILE *f;
>> +    int ret = -1;
>> +    char line[512];
>> +
>> +    memset(line, 0, sizeof(line));
>> +    f = fopen("/proc/device-tree/system-id", "r");
>> +    if (!f) {
>> +        return ret;
>> +    }
>> +
>> +    if (fgets(line, sizeof(line), f)) {
>> +        snprintf(value, len, "IBM,%s", line);
>
> Why IBM,<system-id>?

There were userspace tools that looking at lparcfg, and were encoded
similarly.

>
>> +        ret = 0;
>> +    }
>> +    fclose(f);
>> +
>> +    return ret;
>
> I think it makes sense to extract the "read a full file into a buffer" 
> logic into a separate function. For bonus points, find a glib function 
> that already does it and use that ;).

Let me search.

>
>> +}
>> +
>> +int32_t kvmppc_get_host_model(char *value, int len)
>> +{
>> +    FILE *f;
>> +    int ret = -1;
>> +    char line[512];
>> +
>> +    memset(line, 0, sizeof(line));
>> +    f = fopen("/proc/device-tree/model", "r");
>> +    if (!f) {
>> +        return ret;
>> +    }
>> +
>> +    if (fgets(line, sizeof(line), f)) {
>> +        snprintf(value, len, "IBM,%s", line);
>
> Same here - wouldn't this be IBM,IBM,foo?

No, it will be IBM,<model>

Regards
Nikunj