[PATCH 1/1] virhostcpu.c: fix 'die' parsing for Power hosts

[Daniel Henrique Barboza <danielhb413@xxxxxxxxx>]

Commit 7b79ee2f78 makes assumptions about die_id parsing in
the sysfs that aren't true for Power hosts. In both Power8
and Power9 the die_id is set to -1:

$ cat /sys/devices/system/cpu/cpu0/topology/die_id
-1

This breaks the parsing being done in virHostCPUGetDie(),
which is using an uInt instead, stopping the VM to start:

virFileReadValueUint:4128 : internal error: Invalid unsigned integer
value '-1' in file '/sys/devices/system/cpu/cpu0/topology/die_id'

This isn't necessarily a PowerPC only behavior. Linux kernel commit
0e344d8c70 added in the former Documentation/cputopology.txt, now
Documentation/admin-guide/cputopology.rst, that:

---
To be consistent on all architectures, include/linux/topology.h
provides default definitions for any of the above macros that are
not defined by include/asm-XXX/topology.h:

1) topology_physical_package_id: -1
2) topology_die_id: -1
(...)
---

This means that it might be expected that an architecture that
does not implement the die_id element will mark it as -1 in
sysfs.

It is not required to change die_id implementation from uInt to
Int because of that. Instead, let's change the parsing of the
die_id in virHostCPUGetDie() to read an integer value and, in
case it's -1, default it to zero like in case of file not found.
This is enough to solve the issue Power hosts are experiencing.

Fixes: 7b79ee2f78bbf2af76df2f6466919e19ae05aeeb
Signed-off-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>
---
 src/util/virhostcpu.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c
index c1b39e772a..8d7841517e 100644
--- a/src/util/virhostcpu.c
+++ b/src/util/virhostcpu.c
@@ -220,15 +220,20 @@ virHostCPUGetSocket(unsigned int cpu, unsigned int *socket)
 int
 virHostCPUGetDie(unsigned int cpu, unsigned int *die)
 {
-    int ret = virFileReadValueUint(die,
-                                   "%s/cpu/cpu%u/topology/die_id",
-                                   SYSFS_SYSTEM_PATH, cpu);
+    int die_id;
+    int ret = virFileReadValueInt(&die_id,
+                                  "%s/cpu/cpu%u/topology/die_id",
+                                  SYSFS_SYSTEM_PATH, cpu);
 
-    /* If the file is not there, it's 0 */
-    if (ret == -2)
+    /* If the file is not there, it's 0.
+     * PowerPC hosts can report die_id = -1, which for our
+     * case here it's the same as absent file. */
+    if (ret == -2 || die_id < 0)
         *die = 0;
     else if (ret < 0)
         return -1;
+    else
+        *die = die_id;
 
     return 0;
 }
-- 
2.24.1