Re: [PATCH 3/3] irqchip/riscv-imsic: Remove global nr_guest_files after KVM AIA per-HART conversion

[Inochi Amaoto <inochiama@gmail.com>]

On Wed, Apr 22, 2026 at 11:09:30AM +0800, Guo Ren wrote:
> Hi all,
> 
> This patch simply removed `nr_guest_files`, which is suboptimal. For
> v2, I will keep `nr_guest_files` inside `struct imsic_local_config`
> (per-HART) and compute the effective HGEI count in
> `kvm_riscv_aia_enable()` as:
> 
> min(hgctrl->nr_hgei, lc->nr_guest_files)
> 
> This provides a more accurate and robust per-HART configuration.
> 
> Here are the updated two patches for your review:
> 
>     irqchip/riscv-imsic: Move nr_guest_files to per-HART local config
> 
>     With the recent KVM AIA per-HART HGEI conversion, the global
>     nr_guest_files is no longer appropriate. Different HARTs in
>     heterogeneous SoCs may have different numbers of guest interrupt
>     files.
> 
>     Move `nr_guest_files` from `struct imsic_global_config` to
>     `struct imsic_local_config`, and compute it per-CPU in
>     imsic_setup_state() based on the actual MMIO guest file region size.
> 
>     Update the related comment to reflect that KVM now uses the
>     per-HART value.
> 
>     This eliminates the last global assumption about guest files and
>     completes the per-HART conversion series for RISC-V AIA/IMSIC.
> 
>     Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
> 
> diff --git a/drivers/irqchip/irq-riscv-imsic-state.c
> b/drivers/irqchip/irq-riscv-imsic-state.c
> index e3ed874d89e7..3d455ef43298 100644
> --- a/drivers/irqchip/irq-riscv-imsic-state.c
> +++ b/drivers/irqchip/irq-riscv-imsic-state.c
> @@ -784,7 +784,7 @@ 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_guest_files,
> nr_handlers = 0;
> +       u32 i, j, index, nr_parent_irqs, nr_mmios, nr_handlers = 0;
>         struct imsic_global_config *global;
>         struct imsic_local_config *local;
>         void __iomem **mmios_va = NULL;
> @@ -878,7 +878,6 @@ 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) {
> @@ -920,13 +919,13 @@ int __init imsic_setup_state(struct
> fwnode_handle *fwnode, void *opaque)
>                 local->msi_va = mmios_va[index] + reloff;
> 
>                 /*
> -                * KVM uses global->nr_guest_files to determine the
> available guest
> +                * KVM uses local->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);
> +               local->nr_guest_files =
> +                       (resource_size(&mmios[index]) - reloff) /
> IMSIC_MMIO_PAGE_SZ - 1;
> 

The min is still required, otherwise the local->nr_guest_files can be
bigger than BIT(global->guest_index_bits) - 1, which is the max number
of the guest interrupt files that a hart can have. This condition is
true if the IMSIC group has more than one harts.

Regards,
Inochi

>                 nr_handlers++;
>         }
> diff --git a/include/linux/irqchip/riscv-imsic.h
> b/include/linux/irqchip/riscv-imsic.h
> index 4b348836de7a..13e8bd7ff4b4 100644
> --- a/include/linux/irqchip/riscv-imsic.h
> +++ b/include/linux/irqchip/riscv-imsic.h
> @@ -40,6 +40,9 @@
>  struct imsic_local_config {
>         phys_addr_t                             msi_pa;
>         void __iomem                            *msi_va;
> +
> +       /* Number of guest interrupt files per core */
> +       u32                                     nr_guest_files;
>  };
> 
>  struct imsic_global_config {
> @@ -68,9 +71,6 @@ 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;
>  };
> 
> ------------------------
> The other one:
> 
>     RISC-V: KVM: AIA: Use per-HART IMSIC guest files to compute final HGEI count
> 
>     Now that `nr_guest_files` has been moved to `struct imsic_local_config`
>     and is computed per-HART, KVM must respect the actual number of guest
>     interrupt files available on each HART when setting up HGEI.
> 
>     In `kvm_riscv_aia_enable()`:
> 
>      - Retrieve the per-CPU IMSIC local config
>      - Take `min(hgctrl->nr_hgei, lc->nr_guest_files)` as the final usable
>        HGEI count for this HART
>      - Use the result to initialize `free_bitmap`
> 
>     This ensures correct HGEI allocation on heterogeneous RISC-V SoCs
>     where different cores may have different IMSIC guest file counts, and
>     completes the per-HART conversion series.
> 
>     Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
> 
> diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c
> index 70ff1d25dd99..a5f4b7fe1dce 100644
> --- a/arch/riscv/kvm/aia.c
> +++ b/arch/riscv/kvm/aia.c
> @@ -534,6 +534,9 @@ static void aia_hgei_exit(void)
>  void kvm_riscv_aia_enable(void)
>  {
>         struct aia_hgei_control *hgctrl;
> +       const struct imsic_global_config *gc;
> +       const struct imsic_local_config *lc;
> +       unsigned int nr_hgei;
> 
>         if (!kvm_riscv_aia_available())
>                 return;
> @@ -547,8 +550,13 @@ void kvm_riscv_aia_enable(void)
>         if (hgctrl->nr_hgei)
>                 hgctrl->nr_hgei--;
> 
> -       if (hgctrl->nr_hgei) {
> -               hgctrl->free_bitmap = BIT(hgctrl->nr_hgei + 1) - 1;
> +       gc = imsic_get_global_config();
> +       lc = (gc) ? this_cpu_ptr(gc->local) : NULL;
> +       if (lc)
> +               nr_hgei = min(hgctrl->nr_hgei, lc->nr_guest_files);
> +
> +       if (nr_hgei) {
> +               hgctrl->free_bitmap = BIT(nr_hgei + 1) - 1;
>                 hgctrl->free_bitmap &= ~BIT(0);
>         } else {
>                 hgctrl->free_bitmap = 0;
> 
> 
> On Tue, Apr 21, 2026 at 10:55 PM <guoren@kernel.org> wrote:
> >
> > From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>
> >
> > With the recent KVM AIA changes, HGEI line management is now fully
> > per-CPU (via struct aia_hgei_control::nr_hgei) and the global
> > kvm_riscv_aia_nr_hgei has been replaced by a simple enabled flag.
> > The IMSIC driver no longer needs to compute and enforce a global
> > minimum number of guest interrupt files across all HARTs.
> >
> > Remove:
> >  - `u32 nr_guest_files` from `struct imsic_global_config`
> >  - the initial `BIT(global->guest_index_bits) - 1` assignment
> >  - the entire per-CPU MMIO-based min() calculation and its comment
> >    (which was specifically there to protect old KVM)
> >
> > The per-HART guest file count is already handled locally in
> > `imsic_local_config` during the parent IRQ loop, so this global
> > field was redundant.
> >
> > This completes the cleanup series, eliminates the last global
> > assumption about guest files, and improves support for heterogeneous
> > (big.LITTLE / multi-vendor) RISC-V platforms.
> >
> > Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
> > ---
> >  drivers/irqchip/irq-riscv-imsic-state.c | 12 +-----------
> >  include/linux/irqchip/riscv-imsic.h     |  3 ---
> >  2 files changed, 1 insertion(+), 14 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-riscv-imsic-state.c b/drivers/irqchip/irq-riscv-imsic-state.c
> > index e3ed874d89e7..fef27247a34f 100644
> > --- a/drivers/irqchip/irq-riscv-imsic-state.c
> > +++ b/drivers/irqchip/irq-riscv-imsic-state.c
> > @@ -784,7 +784,7 @@ 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_guest_files, nr_handlers = 0;
> > +       u32 i, j, index, nr_parent_irqs, nr_mmios, nr_handlers = 0;
> >         struct imsic_global_config *global;
> >         struct imsic_local_config *local;
> >         void __iomem **mmios_va = NULL;
> > @@ -878,7 +878,6 @@ 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) {
> > @@ -919,15 +918,6 @@ 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 4b348836de7a..7f3ff5c5ea53 100644
> > --- a/include/linux/irqchip/riscv-imsic.h
> > +++ b/include/linux/irqchip/riscv-imsic.h
> > @@ -68,9 +68,6 @@ 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;
> >  };
> > --
> > 2.40.1
> >
> 
> 
> --
> Best Regards
>  Guo Ren
> 
> -- 
> kvm-riscv mailing list
> kvm-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kvm-riscv

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