Re: [PATCH] virresctrl: Fix updating the mask for a cache resource

Daniel Henrique Barboza <danielhb413@xxxxxxxxx> · Wed, 7 Jul 2021 10:30:16 -0300

On 7/2/21 4:23 AM, Vinayak Kale wrote:
In 'virResctrlAllocUpdateMask', mask is updated only if 'previous mask' is NULL.

By default, the bitmask for a cache resource for a VM is initialized with
'default-resctrl-group' bitmask. So the 'previous mask' would not be NULL and
mask won't get updated if cachetune is configured for a VM. This causes libvirt
to use same bitmask as 'default-resctrl-group' bitmask for a cache resource for
a VM. This patch fixes the issue.

Fixes: d8a354954aba9cd45ab0317915a0a2be27c04767

Signed-off-by: Vinayak Kale <vkale@xxxxxxxxxx>
---

I was going to suggest whether cachetune couldn't just overwrite the default
mask if it's configured, but that would just shift the problem somewhere else.

This fix seems adequate.

Reviewed-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>



  src/util/virresctrl.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c
index 35e92022db..a7d36f492c 100644
--- a/src/util/virresctrl.c
+++ b/src/util/virresctrl.c
@@ -1104,8 +1104,10 @@ virResctrlAllocUpdateMask(virResctrlAlloc *alloc,
          VIR_EXPAND_N(a_type->masks, a_type->nmasks,
                       cache - a_type->nmasks + 1);
  
-    if (!a_type->masks[cache])
-        a_type->masks[cache] = virBitmapNewCopy(mask);
+    if (a_type->masks[cache])
+        virBitmapFree(a_type->masks[cache]);
+
+    a_type->masks[cache] = virBitmapNewCopy(mask);
  
      return 0;
  }








