From 456ecdb7a27a651269261dd67d2bcc61f3db89a9 Mon Sep 17 00:00:00 2001 From: "Guo Ren (Alibaba DAMO Academy)" Date: Mon, 25 May 2026 15:19:44 +0530 Subject: [PATCH 1/2] irqchip/riscv-imsic: Add nr_guest_files in per-HART local config Add nr_guest_files in per-HART local config to represent the number of guest files available on a particular HART whereas the nr_guest_files in the global config represents the number of guest files available across all HARTs. This allows KVM RISC-V to use nr_guest_files from per-HART local config for asymmetric big.Little systems. Signed-off-by: Guo Ren (Alibaba DAMO Academy) Acked-by: Thomas Gleixner Signed-off-by: Anup Patel Signed-off-by: Linux RISC-V bot --- drivers/irqchip/irq-riscv-imsic-state.c | 9 ++++----- include/linux/irqchip/riscv-imsic.h | 5 ++++- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/irqchip/irq-riscv-imsic-state.c b/drivers/irqchip/irq-riscv-imsic-state.c index e3ed874d89e73b..b8d1bbbf42f730 100644 --- a/drivers/irqchip/irq-riscv-imsic-state.c +++ b/drivers/irqchip/irq-riscv-imsic-state.c @@ -920,13 +920,12 @@ 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 - * 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. + * KVM uses both local->nr_guest_files and global->nr_guest_files + * to determine the available guest interrupt files on each CPU. */ 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 = min((BIT(global->guest_index_bits) - 1), nr_guest_files); + global->nr_guest_files = min(global->nr_guest_files, local->nr_guest_files); nr_handlers++; } diff --git a/include/linux/irqchip/riscv-imsic.h b/include/linux/irqchip/riscv-imsic.h index 4b348836de7ada..61af3a5bea09bd 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-HART */ + u32 nr_guest_files; }; struct imsic_global_config { @@ -68,7 +71,7 @@ struct imsic_global_config { /* Number of guest interrupt identities */ u32 nr_guest_ids; - /* Number of guest interrupt files per core */ + /* Number of guest interrupt files across all HARTs */ u32 nr_guest_files; /* Per-CPU IMSIC addresses */ From 0bd32bcca36dba79316e9acbf5c42e86977ec3e2 Mon Sep 17 00:00:00 2001 From: "Guo Ren (Alibaba DAMO Academy)" Date: Mon, 25 May 2026 15:19:45 +0530 Subject: [PATCH 2/2] RISC-V: KVM: AIA: Make HGEI number management fully per-CPU Previously, the number of Hypervisor Guest External Interrupt (HGEI) lines was stored in a single global variable `kvm_riscv_aia_nr_hgei` and assumed to be the same for all HARTs. This assumption does not hold on heterogeneous RISC-V SoCs where different cores may expose different HGEIE CSR widths. Introduce `nr_hgei` field into the per-CPU `struct aia_hgei_control` and probe the actual supported HGEI count for the current HART in `kvm_riscv_aia_enable()` using the standard RISC-V CSR probe technique: csr_write(CSR_HGEIE, -1UL); nr = fls_long(csr_read(CSR_HGEIE)); if (nr) nr--; All HGEI allocation, free and disable paths (`kvm_riscv_aia_free_hgei()`, `kvm_riscv_aia_disable()`, etc.) now use the per-CPU value instead of the global one. The global `kvm_riscv_aia_nr_hgei` now represents the minimum number of HGEI lines across HARTs and can be used to check whether HGEI support is available or not. This makes KVM AIA robust on big.LITTLE-style asymmetric platforms. Signed-off-by: Guo Ren (Alibaba DAMO Academy) Signed-off-by: Anup Patel Signed-off-by: Linux RISC-V bot --- arch/riscv/include/asm/kvm_aia.h | 2 +- arch/riscv/kvm/aia.c | 88 +++++++++++++++++++------------- arch/riscv/kvm/aia_device.c | 4 +- arch/riscv/kvm/main.c | 8 +-- 4 files changed, 60 insertions(+), 42 deletions(-) diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/asm/kvm_aia.h index b04ecdd1a860bd..c67ec5ac0a146b 100644 --- a/arch/riscv/include/asm/kvm_aia.h +++ b/arch/riscv/include/asm/kvm_aia.h @@ -79,7 +79,7 @@ struct kvm_vcpu_aia { #define irqchip_in_kernel(k) ((k)->arch.aia.in_kernel) -extern unsigned int kvm_riscv_aia_nr_hgei; +extern atomic_t kvm_riscv_aia_nr_hgei; extern unsigned int kvm_riscv_aia_max_ids; DECLARE_STATIC_KEY_FALSE(kvm_riscv_aia_available); #define kvm_riscv_aia_available() \ diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c index 5ec503288555d1..bafb009c5ce559 100644 --- a/arch/riscv/kvm/aia.c +++ b/arch/riscv/kvm/aia.c @@ -21,13 +21,15 @@ struct aia_hgei_control { raw_spinlock_t lock; + bool free_bitmap_initialized; unsigned long free_bitmap; struct kvm_vcpu *owners[BITS_PER_LONG]; + unsigned int nr_hgei; }; static DEFINE_PER_CPU(struct aia_hgei_control, aia_hgei); static int hgei_parent_irq; -unsigned int kvm_riscv_aia_nr_hgei; +atomic_t kvm_riscv_aia_nr_hgei; unsigned int kvm_riscv_aia_max_ids; DEFINE_STATIC_KEY_FALSE(kvm_riscv_aia_available); @@ -452,7 +454,7 @@ void kvm_riscv_aia_free_hgei(int cpu, int hgei) raw_spin_lock_irqsave(&hgctrl->lock, flags); - if (hgei > 0 && hgei <= kvm_riscv_aia_nr_hgei) { + if (hgei > 0 && hgei <= hgctrl->nr_hgei) { if (!(hgctrl->free_bitmap & BIT(hgei))) { hgctrl->free_bitmap |= BIT(hgei); hgctrl->owners[hgei] = NULL; @@ -486,26 +488,18 @@ static irqreturn_t hgei_interrupt(int irq, void *dev_id) static int aia_hgei_init(void) { - int cpu, rc; - struct irq_domain *domain; struct aia_hgei_control *hgctrl; + struct irq_domain *domain; + int cpu, rc; /* Initialize per-CPU guest external interrupt line management */ for_each_possible_cpu(cpu) { hgctrl = per_cpu_ptr(&aia_hgei, cpu); raw_spin_lock_init(&hgctrl->lock); - if (kvm_riscv_aia_nr_hgei) { - hgctrl->free_bitmap = - BIT(kvm_riscv_aia_nr_hgei + 1) - 1; - hgctrl->free_bitmap &= ~BIT(0); - } else - hgctrl->free_bitmap = 0; + hgctrl->free_bitmap_initialized = false; + hgctrl->free_bitmap = 0; } - /* Skip SGEI interrupt setup for zero guest external interrupts */ - if (!kvm_riscv_aia_nr_hgei) - goto skip_sgei_interrupt; - /* Find INTC irq domain */ domain = irq_find_matching_fwnode(riscv_get_intc_hwnode(), DOMAIN_BUS_ANY); @@ -529,25 +523,60 @@ static int aia_hgei_init(void) return rc; } -skip_sgei_interrupt: return 0; } static void aia_hgei_exit(void) { - /* Do nothing for zero guest external interrupts */ - if (!kvm_riscv_aia_nr_hgei) - return; - /* Free per-CPU SGEI interrupt */ free_percpu_irq(hgei_parent_irq, &aia_hgei); } void kvm_riscv_aia_enable(void) { + const struct imsic_global_config *gc; + const struct imsic_local_config *lc; + struct aia_hgei_control *hgctrl; + unsigned long flags; + int aia_nr_hgei; + if (!kvm_riscv_aia_available()) return; + gc = imsic_get_global_config(); + lc = (gc) ? this_cpu_ptr(gc->local) : NULL; + hgctrl = this_cpu_ptr(&aia_hgei); + + /* Figure-out number of bits in HGEIE */ + csr_write(CSR_HGEIE, -1UL); + hgctrl->nr_hgei = fls_long(csr_read(CSR_HGEIE)); + csr_write(CSR_HGEIE, 0); + if (hgctrl->nr_hgei) + hgctrl->nr_hgei--; + + /* + * Number of usable per-HART HGEI lines should be minimum of + * per-HART IMSIC guest files and number of bits in HGEIE. + */ + if (lc) + hgctrl->nr_hgei = min((ulong)hgctrl->nr_hgei, lc->nr_guest_files); + else + hgctrl->nr_hgei = 0; + + /* Update the number of IMSIC guest files across all HARTs */ + aia_nr_hgei = atomic_read(&kvm_riscv_aia_nr_hgei); + do { + if (aia_nr_hgei <= hgctrl->nr_hgei) + break; + } while (!atomic_try_cmpxchg(&kvm_riscv_aia_nr_hgei, &aia_nr_hgei, hgctrl->nr_hgei)); + + raw_spin_lock_irqsave(&hgctrl->lock, flags); + if (!hgctrl->free_bitmap_initialized) { + hgctrl->free_bitmap = (hgctrl->nr_hgei) ? GENMASK_ULL(hgctrl->nr_hgei, 1) : 0; + hgctrl->free_bitmap_initialized = true; + } + raw_spin_unlock_irqrestore(&hgctrl->lock, flags); + csr_write(CSR_HVICTL, aia_hvictl_value(false)); csr_write(CSR_HVIPRIO1, 0x0); csr_write(CSR_HVIPRIO2, 0x0); @@ -588,7 +617,7 @@ void kvm_riscv_aia_disable(void) raw_spin_lock_irqsave(&hgctrl->lock, flags); - for (i = 0; i <= kvm_riscv_aia_nr_hgei; i++) { + for (i = 0; i <= hgctrl->nr_hgei; i++) { vcpu = hgctrl->owners[i]; if (!vcpu) continue; @@ -628,26 +657,15 @@ int kvm_riscv_aia_init(void) return -ENODEV; gc = imsic_get_global_config(); - /* Figure-out number of bits in HGEIE */ - csr_write(CSR_HGEIE, -1UL); - kvm_riscv_aia_nr_hgei = fls_long(csr_read(CSR_HGEIE)); - csr_write(CSR_HGEIE, 0); - if (kvm_riscv_aia_nr_hgei) - kvm_riscv_aia_nr_hgei--; - - /* - * Number of usable HGEI lines should be minimum of per-HART - * IMSIC guest files and number of bits in HGEIE - */ + /* Set initial value of IMSIC guest files across all HARTs */ if (gc) - kvm_riscv_aia_nr_hgei = min((ulong)kvm_riscv_aia_nr_hgei, - gc->nr_guest_files); + atomic_set(&kvm_riscv_aia_nr_hgei, gc->nr_guest_files); else - kvm_riscv_aia_nr_hgei = 0; + atomic_set(&kvm_riscv_aia_nr_hgei, 0); /* Find number of guest MSI IDs */ kvm_riscv_aia_max_ids = IMSIC_MAX_ID; - if (gc && kvm_riscv_aia_nr_hgei) + if (gc) kvm_riscv_aia_max_ids = gc->nr_guest_ids + 1; /* Initialize guest external interrupt line management */ diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c index 3d1e81e2a36b03..be83c2d5fc308c 100644 --- a/arch/riscv/kvm/aia_device.c +++ b/arch/riscv/kvm/aia_device.c @@ -71,7 +71,7 @@ static int aia_config(struct kvm *kvm, unsigned long type, * external interrupts (i.e. non-zero * VS-level IMSIC pages). */ - if (!kvm_riscv_aia_nr_hgei) + if (!atomic_read(&kvm_riscv_aia_nr_hgei)) return -EINVAL; break; default: @@ -628,7 +628,7 @@ void kvm_riscv_aia_init_vm(struct kvm *kvm) */ /* Initialize default values in AIA global context */ - aia->mode = (kvm_riscv_aia_nr_hgei) ? + aia->mode = (atomic_read(&kvm_riscv_aia_nr_hgei)) ? KVM_DEV_RISCV_AIA_MODE_AUTO : KVM_DEV_RISCV_AIA_MODE_EMUL; aia->nr_ids = kvm_riscv_aia_max_ids - 1; aia->nr_sources = 0; diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c index cb8a65273c1f04..0924c75100a2d0 100644 --- a/arch/riscv/kvm/main.c +++ b/arch/riscv/kvm/main.c @@ -168,10 +168,6 @@ static int __init riscv_kvm_init(void) kvm_info("VMID %ld bits available\n", kvm_riscv_gstage_vmid_bits()); - if (kvm_riscv_aia_available()) - kvm_info("AIA available with %d guest external interrupts\n", - kvm_riscv_aia_nr_hgei); - kvm_riscv_setup_vendor_features(); kvm_register_perf_callbacks(); @@ -182,6 +178,10 @@ static int __init riscv_kvm_init(void) return rc; } + if (kvm_riscv_aia_available()) + kvm_info("AIA available with %d guest external interrupts\n", + atomic_read(&kvm_riscv_aia_nr_hgei)); + return 0; } module_init(riscv_kvm_init);