From f758340da529ccb12531c3f83d5992e912f6c8d5 Mon Sep 17 00:00:00 2001 From: Zeng Heng Date: Mon, 13 Apr 2026 17:00:41 +0800 Subject: 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: 6789fb99282c ("arm_mpam: resctrl: Add CDP emulation") Signed-off-by: Zeng Heng [ morse: Added comment for existing code, added hunk to fix this bug from Ben H ] Reviewed-by: James Morse Signed-off-by: James Morse --- drivers/resctrl/mpam_resctrl.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'drivers/resctrl') diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c index a9938006d0e6..4205fb2ee312 100644 --- a/drivers/resctrl/mpam_resctrl.c +++ b/drivers/resctrl/mpam_resctrl.c @@ -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; -- cgit v1.2.3