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

[Alexander Graf]

On 08.07.14 13:04, Nikunj A Dadhania wrote:
Alexander Graf <ag...@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 <nik...@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.
Yeah, feel free to convert that one too if you like ;).

   
       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?
As Ben already mentioned ;).

+
+    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.
I don't think we own the IBM namespace, so I find this slightly bogus. 
Also why would a host machine have to be made by IBM?
+        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>
Hrm, I just tried to compare this with a pHyp system and can't seem to 
find any /proc/device-tree/host* files. What am I missing?

Alex