From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 9 Apr 2025 13:30:15 +0000 (+0200)
Subject: libxc/PM: correct (not just) error handling in xc_get_cpufreq_para()
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=cf1995fa8a24c7e51e781010680b042f49b38eda;p=xen.git

libxc/PM: correct (not just) error handling in xc_get_cpufreq_para()

From their introduction all xc_hypercall_bounce_pre() uses, when they
failed, would properly cause exit from the function including cleanup,
yet without informing the caller of the failure. Purge the unlock_1
label for being both pointless and mis-named.

An earlier attempt to switch to the usual split between return value and
errno wasn't quite complete.

HWP work made the cleanup of the "available governors" array
conditional, neglecting the fact that the condition used may not be the
condition that was used to allocate the buffer (as the structure field
is updated upon getting back EAGAIN). Since cleanup can be done even if
no buffer was allocated, drop the conditional there again.

Fixes: 4513025a8790 ("libxc: convert sysctl interfaces over to hypercall buffers")
Amends: 73367cf3b4b4 ("libxc: Fix xc_pm API calls to return negative error and stash error in errno")
Fixes: 31e264c672bc ("pmstat&xenpm: Re-arrage for cpufreq union")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
---

diff --git a/tools/libs/ctrl/xc_pm.c b/tools/libs/ctrl/xc_pm.c
index b27b45c3dc..ff7b5ada05 100644
--- a/tools/libs/ctrl/xc_pm.c
+++ b/tools/libs/ctrl/xc_pm.c
@@ -212,10 +212,7 @@ int xc_get_cpufreq_para(xc_interface *xch, int cpuid,
     DECLARE_NAMED_HYPERCALL_BOUNCE(scaling_available_governors,
 			 user_para->scaling_available_governors,
 			 user_para->gov_num * CPUFREQ_NAME_LEN * sizeof(char), XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
-
-    bool has_num = user_para->cpu_num &&
-                     user_para->freq_num &&
-                     user_para->gov_num;
+    bool has_num = user_para->cpu_num && user_para->freq_num;
 
     if ( has_num )
     {
@@ -226,12 +223,15 @@ int xc_get_cpufreq_para(xc_interface *xch, int cpuid,
             errno = EINVAL;
             return -1;
         }
-        if ( xc_hypercall_bounce_pre(xch, affected_cpus) )
-            goto unlock_1;
-        if ( xc_hypercall_bounce_pre(xch, scaling_available_frequencies) )
+        ret = xc_hypercall_bounce_pre(xch, affected_cpus);
+        if ( ret )
+            return ret;
+        ret = xc_hypercall_bounce_pre(xch, scaling_available_frequencies);
+        if ( ret )
             goto unlock_2;
-        if ( user_para->gov_num &&
-             xc_hypercall_bounce_pre(xch, scaling_available_governors) )
+        if ( user_para->gov_num )
+            ret = xc_hypercall_bounce_pre(xch, scaling_available_governors);
+        if ( ret )
             goto unlock_3;
 
         set_xen_guest_handle(sys_para->affected_cpus, affected_cpus);
@@ -256,12 +256,11 @@ int xc_get_cpufreq_para(xc_interface *xch, int cpuid,
             user_para->cpu_num  = sys_para->cpu_num;
             user_para->freq_num = sys_para->freq_num;
             user_para->gov_num  = sys_para->gov_num;
-            ret = -errno;
         }
 
         if ( has_num )
             goto unlock_4;
-        goto unlock_1;
+        return ret;
     }
     else
     {
@@ -298,13 +297,12 @@ int xc_get_cpufreq_para(xc_interface *xch, int cpuid,
     }
 
 unlock_4:
-    if ( user_para->gov_num )
-        xc_hypercall_bounce_post(xch, scaling_available_governors);
+    xc_hypercall_bounce_post(xch, scaling_available_governors);
 unlock_3:
     xc_hypercall_bounce_post(xch, scaling_available_frequencies);
 unlock_2:
     xc_hypercall_bounce_post(xch, affected_cpus);
-unlock_1:
+
     return ret;
 }