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

Inochi Amaoto
2026-04-23T04:20:45Z

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
>
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