Re: [External] [PATCH RFC v2 08/17] RISC-V: QoS: add resctrl interface for CBQRI controllers

On Wed, Mar 25, 2026 at 10:09:01AM +0800, yunhui cui wrote:
> Hi Drew,
> 
> On Thu, Jan 29, 2026 at 4:28 AM Drew Fustini <[email protected]> wrote:
> >
> > Add interface for CBQRI controller drivers to make use of the resctrl
> > filesystem.
> >
> > Co-developed-by: Adrien Ricciardi <[email protected]>
> > Signed-off-by: Adrien Ricciardi <[email protected]>
> > Signed-off-by: Drew Fustini <[email protected]>
> > ---
> >  arch/riscv/kernel/qos/qos_resctrl.c | 1192 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 1192 insertions(+)
> >
> > diff --git a/arch/riscv/kernel/qos/qos_resctrl.c b/arch/riscv/kernel/qos/qos_resctrl.c
> > new file mode 100644
> > index 000000000000..d500098599d2
> > --- /dev/null
> > +++ b/arch/riscv/kernel/qos/qos_resctrl.c
> > @@ -0,0 +1,1192 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +
> > +#define pr_fmt(fmt) "qos: resctrl: " fmt
> > +
> > +#include <linux/slab.h>
> > +#include <linux/err.h>
> > +#include <linux/riscv_qos.h>
> > +#include <linux/resctrl.h>
> > +#include <linux/types.h>
> > +#include <asm/csr.h>
> > +#include <asm/qos.h>
> > +#include "internal.h"
> > +
> > +#define MAX_CONTROLLERS 6
> > +static struct cbqri_controller controllers[MAX_CONTROLLERS];
> 
> We can get the total number of controllers, so we'll allocate dynamically.

I've made a lot of improvements but am still making more changes based
on the feedback from Reinette and you. I'm hoping to finish and send a
new revision of the series but in the meantime my work-in-progress is
b4/ssqosid-cbqri-rqsc [1].

I have dropped this static array and now just use a list of controllers.
It is populated by drivers/acpi/riscv/rqsc.c [2] and iterated through by
qos_resctrl_setup() in arch/riscv/kernel/qos/qos_resctrl.c [3].

[1] https://github.com/tt-fustini/linux/tree/b4/ssqosid-cbqri-rqsc
[2] https://github.com/tt-fustini/linux/blob/b4/ssqosid-cbqri-rqsc/drivers/acpi/riscv/rqsc.c
[3] https://github.com/tt-fustini/linux/blob/b4/ssqosid-cbqri-rqsc/arch/riscv/kernel/qos/qos_resctrl.c

> > +static int qos_resctrl_add_controller_domain(struct cbqri_controller *ctrl, int *id)
[..]

> 1. Wrap this into a function.
> 
> 2. Also, mweight controller support needs to be added here.
> We may need to add RDT_RESOURCE_MB_WEIGHT to the enumeration:
> enum resctrl_res_level {
> ...
> RDT_RESOURCE_MB_WEIGHT,
> ...
> };
> 
> 3. We need to implement cbqri_set_mweight() and cbqri_get_mweight().

I think this could be a good way to implement mweight but I am planning
to intiailly support justI think this could be a good way to implement
mweight but I am planning to intiailly support just rbwb
 
> 4. We need to add monitor controllers (domains) for both capacity and MBW.

I don't want to attempt to support bandwidth monitoring until there is
progress in resctrl for support of cpu-less memory devices as this is a
concern for mpam too. However, it should be possible to support cache
occupancy monitoring.

[..]
> > +       pr_info("exposed_alloc_capable = %d", exposed_alloc_capable);
> > +       pr_info("exposed_mon_capable = %d", exposed_mon_capable);
> > +       pr_info("exposed_cdp_l2_capable = %d", exposed_cdp_l2_capable);
> > +       pr_info("exposed_cdp_l3_capable = %d", exposed_cdp_l3_capable);
> 
> One line of pr_info? Print total controllers, capacity and MBW counts

Good idea, I'll do that.

Thanks,
Drew