[PATCH] x86/resctrl: Do not round up mba_MBps values in schemata file

[Tony Luck]

When the mba_MBps mount option is used Linux initializes the
MBA control values in the schemata file to MBA_MAX_MBPS (which
is defined as U32_MAX). So the schemata file contains this line:

 MB:0=4294967295;1=4294967295

If a user edits the schemata file with vi(1) (or other editor) and
simply writes that line back, it gets changed to:

  MB:0=   4;1=   4

which sets maximum bandwidth to a very low value.

This happens because bw_validate() unconditionally rounds user supplied
values up to next multiple of r->membw.bw_gran. That results in a value
that will not fit into d->mbps_val[closid].

Rounding up only makes sense when mba_MBps is not enabled and control
values are expressed as percentage values.

Skip the roundup() when mba_MBps is enabled.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 50fa1fe9a073..ac636366c0cb 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -55,7 +55,7 @@ static bool bw_validate(char *buf, unsigned long *data, struct rdt_resource *r)
 		return false;
 	}
 
-	*data = roundup(bw, (unsigned long)r->membw.bw_gran);
+	*data = is_mba_sc(r) ? bw : roundup(bw, (unsigned long)r->membw.bw_gran);
 	return true;
 }
 
-- 
2.46.1