linux-kernel - Re: [External] Re: [PATCH v5] irqchip/riscv-imsic: Adjust the number of available guest irq files

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Message-ID: <CAAhSdy0YGdKjdzROdyE6gG=LCvHd7nQbWuW4a+thB5vr47QuSQ@mail.gmail.com>
Date: Mon, 26 Jan 2026 19:07:52 +0530
From: Anup Patel <anup@...infault.org>
To: Xu Lu <luxu.kernel@...edance.com>
Cc: atish.patra@...ux.dev, pjw@...nel.org, palmer@...belt.com, 
	aou@...s.berkeley.edu, alex@...ti.fr, tglx@...utronix.de, kvm@...r.kernel.org, 
	kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v5] irqchip/riscv-imsic: Adjust the number
 of available guest irq files

On Mon, Jan 26, 2026 at 4:37 PM Xu Lu <luxu.kernel@...edance.com> wrote:
>
> On Mon, Jan 26, 2026 at 6:54 PM Anup Patel <anup@...infault.org> wrote:
> >
> > On Sun, Jan 4, 2026 at 7:05 PM Xu Lu <luxu.kernel@...edance.com> wrote:
> > >
> > > Currently, KVM assumes the minimum of implemented HGEIE bits and
> > > "BIT(gc->guest_index_bits) - 1" as the number of guest files available
> > > across all CPUs. This will not work when CPUs have different number
> > > of guest files because KVM may incorrectly allocate a guest file on a
> > > CPU with fewer guest files.
> > >
> > > To address above, during initialization, calculate the number of
> > > available guest interrupt files according to MMIO resources and
> > > constrain the number of guest interrupt files that can be allocated
> > > by KVM.
> > >
> > > Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
> >
> > Please carry Reviewed-by and Acked-by tags obtained in previous
> > revisions. Next time, I will not take the patch if previous tags are
> > missing.
>
> Sorry about that. I thought the Reviewed-by and Acked-by tags belong
> to the previous version so didn't carry them.
>
> >
> > Queued this patch for Linux-6.20.
>
> Do I still need to resend the patch with Reviewed-by and Acked-by tags?

I have included the tags at the time of the merging patch.

Regards,
Anup

>
> Best regards,
> Xu Lu
>
> >
> > Regards,
> > Anup
> >
> > > ---
> > >  arch/riscv/kvm/aia.c                    |  2 +-
> > >  drivers/irqchip/irq-riscv-imsic-state.c | 12 +++++++++++-
> > >  include/linux/irqchip/riscv-imsic.h     |  3 +++
> > >  3 files changed, 15 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c
> > > index dad3181856600..cac3c2b51d724 100644
> > > --- a/arch/riscv/kvm/aia.c
> > > +++ b/arch/riscv/kvm/aia.c
> > > @@ -630,7 +630,7 @@ int kvm_riscv_aia_init(void)
> > >          */
> > >         if (gc)
> > >                 kvm_riscv_aia_nr_hgei = min((ulong)kvm_riscv_aia_nr_hgei,
> > > -                                           BIT(gc->guest_index_bits) - 1);
> > > +                                           gc->nr_guest_files);
> > >         else
> > >                 kvm_riscv_aia_nr_hgei = 0;
> > >
> > > diff --git a/drivers/irqchip/irq-riscv-imsic-state.c b/drivers/irqchip/irq-riscv-imsic-state.c
> > > index dc95ad856d80a..e8f20efb028be 100644
> > > --- a/drivers/irqchip/irq-riscv-imsic-state.c
> > > +++ b/drivers/irqchip/irq-riscv-imsic-state.c
> > > @@ -794,7 +794,7 @@ static int __init imsic_parse_fwnode(struct fwnode_handle *fwnode,
> > >
> > >  int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
> > >  {
> > > -       u32 i, j, index, nr_parent_irqs, nr_mmios, nr_handlers = 0;
> > > +       u32 i, j, index, nr_parent_irqs, nr_mmios, nr_guest_files, nr_handlers = 0;
> > >         struct imsic_global_config *global;
> > >         struct imsic_local_config *local;
> > >         void __iomem **mmios_va = NULL;
> > > @@ -888,6 +888,7 @@ int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
> > >         }
> > >
> > >         /* Configure handlers for target CPUs */
> > > +       global->nr_guest_files = BIT(global->guest_index_bits) - 1;
> > >         for (i = 0; i < nr_parent_irqs; i++) {
> > >                 rc = imsic_get_parent_hartid(fwnode, i, &hartid);
> > >                 if (rc) {
> > > @@ -928,6 +929,15 @@ int __init imsic_setup_state(struct fwnode_handle *fwnode, void *opaque)
> > >                 local->msi_pa = mmios[index].start + reloff;
> > >                 local->msi_va = mmios_va[index] + reloff;
> > >
> > > +               /*
> > > +                * KVM uses global->nr_guest_files to determine the available guest
> > > +                * interrupt files on each CPU. Take the minimum number of guest
> > > +                * interrupt files across all CPUs to avoid KVM incorrectly allocating
> > > +                * an unexisted or unmapped guest interrupt file on some CPUs.
> > > +                */
> > > +               nr_guest_files = (resource_size(&mmios[index]) - reloff) / IMSIC_MMIO_PAGE_SZ - 1;
> > > +               global->nr_guest_files = min(global->nr_guest_files, nr_guest_files);
> > > +
> > >                 nr_handlers++;
> > >         }
> > >
> > > diff --git a/include/linux/irqchip/riscv-imsic.h b/include/linux/irqchip/riscv-imsic.h
> > > index 7494952c55187..43aed52385008 100644
> > > --- a/include/linux/irqchip/riscv-imsic.h
> > > +++ b/include/linux/irqchip/riscv-imsic.h
> > > @@ -69,6 +69,9 @@ struct imsic_global_config {
> > >         /* Number of guest interrupt identities */
> > >         u32                                     nr_guest_ids;
> > >
> > > +       /* Number of guest interrupt files per core */
> > > +       u32                                     nr_guest_files;
> > > +
> > >         /* Per-CPU IMSIC addresses */
> > >         struct imsic_local_config __percpu      *local;
> > >  };
> > > --
> > > 2.20.1
> > >
> > >