Commit f758340d authored by Zeng Heng's avatar Zeng Heng Committed by James Morse
Browse files

arm_mpam: resctrl: Fix MBA CDP alloc_capable handling on unmount 



The code to set MBA's alloc_capable to true appears to be trying to
restore alloc_capable on unmount. This can never work because
resctrl_arch_set_cdp_enabled() is never invoked with RDT_RESOURCE_MBA
as the rid parameter. Consequently,
mpam_resctrl_controls[RDT_RESOURCE_MBA].cdp_enabled always remains false.

The alloc_capable setting in resctrl_arch_set_cdp_enabled() is to
re-enable MBA if the caller opts in to separate control values using
CDP for this resource. This doesn't happen today.

Add a comment to describe this.

However a bug remains where MBA allocation is permanently disabled after
the mount with CDP option. Remounting without CDP cannot restore the MBA
partition capability.

Add a check to re-enable MBA when CDP is disabled, which happens on
unmount.

Fixes: 6789fb99 ("arm_mpam: resctrl: Add CDP emulation")
Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
[ morse: Added comment for existing code, added hunk to fix this bug from
  Ben H ]
Reviewed-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
parent 4ce0a2cc

drivers/resctrl/mpam_resctrl.c

+8 −0
Original line number Diff line number Diff line
@@ -220,10 +220,18 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level rid, bool enable) 
	if (cdp_enabled && !mpam_resctrl_controls[RDT_RESOURCE_MBA].cdp_enabled)

		mpam_resctrl_controls[RDT_RESOURCE_MBA].resctrl_res.alloc_capable = false;



	/*

	 * If resctrl has attempted to enable CDP on MBA, re-enable MBA as two

	 * configurations will be provided so there is no aliasing problem.

	 */

	if (mpam_resctrl_controls[RDT_RESOURCE_MBA].cdp_enabled &&

	    mpam_resctrl_controls[RDT_RESOURCE_MBA].class)

		mpam_resctrl_controls[RDT_RESOURCE_MBA].resctrl_res.alloc_capable = true;



	/* On unmount when CDP is disabled, re-enable MBA */

	if (!cdp_enabled && mpam_resctrl_controls[RDT_RESOURCE_MBA].class)

		mpam_resctrl_controls[RDT_RESOURCE_MBA].resctrl_res.alloc_capable = true;



	if (enable) {

		if (mpam_partid_max < 1)

			return -EINVAL;