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

Guo Ren
2026-04-22T03:09:46Z

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;

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