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KVM: selftests: Add helpers to probe for NUMA support, and multi-node systems

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Add NUMA helpers to probe for support/availability and to check if the
test is running on a multi-node system.  The APIs will be used to verify
guest_memfd NUMA support.

Signed-off-by: Shivank Garg <shivankg@amd.com>
[sean: land helpers in numaif.h, add comments, tweak names]
Link: https://lore.kernel.org/r/20251016172853.52451-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Shivank Garg
2025-10-16 10:28:51 -07:00
committed by Sean Christopherson
parent fe7baebb99
commit e698e89b3e
1 changed files with 52 additions and 0 deletions
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52
tools/testing/selftests/kvm/include/numaif.h
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@@ -4,6 +4,8 @@
#ifndef SELFTEST_KVM_NUMAIF_H
#define SELFTEST_KVM_NUMAIF_H
#include <dirent.h>
#include <linux/mempolicy.h>
#include "kvm_syscalls.h"
@@ -28,4 +30,54 @@ KVM_SYSCALL_DEFINE(mbind, 6, void *, addr, unsigned long, size, int, mode,
const unsigned long *, nodemask, unsigned long, maxnode,
unsigned int, flags);
static inline int get_max_numa_node(void)
{
struct dirent *de;
int max_node = 0;
DIR *d;
/*
* Assume there's a single node if the kernel doesn't support NUMA,
* or if no nodes are found.
*/
d = opendir("/sys/devices/system/node");
if (!d)
return 0;
while ((de = readdir(d)) != NULL) {
int node_id;
char *endptr;
if (strncmp(de->d_name, "node", 4) != 0)
continue;
node_id = strtol(de->d_name + 4, &endptr, 10);
if (*endptr != '\0')
continue;
if (node_id > max_node)
max_node = node_id;
}
closedir(d);
return max_node;
}
static bool is_numa_available(void)
{
/*
* Probe for NUMA by doing a dummy get_mempolicy(). If the syscall
* fails with ENOSYS, then the kernel was built without NUMA support.
* if the syscall fails with EPERM, then the process/user lacks the
* necessary capabilities (CAP_SYS_NICE).
*/
return !get_mempolicy(NULL, NULL, 0, NULL, 0) ||
(errno != ENOSYS && errno != EPERM);
}
static inline bool is_multi_numa_node_system(void)
{
return is_numa_available() && get_max_numa_node() >= 1;
}
#endif /* SELFTEST_KVM_NUMAIF_H */