[PATCH v3 8/8] RISC-V: KVM: Implement guest external interrupt line management

Anup Patel
2023-04-03T09:35:18Z

The RISC-V host will have one guest external interrupt line for each
VS-level IMSICs associated with a HART. The guest external interrupt
lines are per-HART resources and hypervisor can use HGEIE, HGEIP, and
HIE CSRs to manage these guest external interrupt lines.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
arch/riscv/include/asm/kvm_aia.h | 10 ++
arch/riscv/kvm/aia.c | 241 +++++++++++++++++++++++++++++++
arch/riscv/kvm/main.c | 3 +-
arch/riscv/kvm/vcpu.c | 2 +
4 files changed, 255 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/asm/kvm_aia.h
index 1de0717112e5..0938e0cadf80 100644
--- a/arch/riscv/include/asm/kvm_aia.h
+++ b/arch/riscv/include/asm/kvm_aia.h
@@ -44,10 +44,15 @@ struct kvm_vcpu_aia {

#define irqchip_in_kernel(k) ((k)->arch.aia.in_kernel)

+extern unsigned int kvm_riscv_aia_nr_hgei;
DECLARE_STATIC_KEY_FALSE(kvm_riscv_aia_available);
#define kvm_riscv_aia_available() \
static_branch_unlikely(&kvm_riscv_aia_available)

+static inline void kvm_riscv_vcpu_aia_imsic_release(struct kvm_vcpu *vcpu)
+{
+}
+
#define KVM_RISCV_AIA_IMSIC_TOPEI (ISELECT_MASK + 1)
static inline int kvm_riscv_vcpu_aia_imsic_rmw(struct kvm_vcpu *vcpu,
unsigned long isel,
@@ -119,6 +124,11 @@ static inline void kvm_riscv_aia_destroy_vm(struct kvm *kvm)
{
}

+int kvm_riscv_aia_alloc_hgei(int cpu, struct kvm_vcpu *owner,
+ void __iomem **hgei_va, phys_addr_t *hgei_pa);
+void kvm_riscv_aia_free_hgei(int cpu, int hgei);
+void kvm_riscv_aia_wakeon_hgei(struct kvm_vcpu *owner, bool enable);
+
void kvm_riscv_aia_enable(void);
void kvm_riscv_aia_disable(void);
int kvm_riscv_aia_init(void);
diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c
index d530912f28bc..1264783e7c4d 100644
--- a/arch/riscv/kvm/aia.c
+++ b/arch/riscv/kvm/aia.c
@@ -7,11 +7,46 @@
* Anup Patel <apatel@ventanamicro.com>
*/

+#include <linux/bitops.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
#include <linux/kvm_host.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
#include <asm/hwcap.h>

+struct aia_hgei_control {
+ raw_spinlock_t lock;
+ unsigned long free_bitmap;
+ struct kvm_vcpu *owners[BITS_PER_LONG];
+};
+static DEFINE_PER_CPU(struct aia_hgei_control, aia_hgei);
+static int hgei_parent_irq;
+
+unsigned int kvm_riscv_aia_nr_hgei;
DEFINE_STATIC_KEY_FALSE(kvm_riscv_aia_available);

+static int aia_find_hgei(struct kvm_vcpu *owner)
+{
+ int i, hgei;
+ unsigned long flags;
+ struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+
+ hgei = -1;
+ for (i = 1; i <= kvm_riscv_aia_nr_hgei; i++) {
+ if (hgctrl->owners[i] == owner) {
+ hgei = i;
+ break;
+ }
+ }
+
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
+
+ return hgei;
+}
+
static void aia_set_hvictl(bool ext_irq_pending)
{
unsigned long hvictl;
@@ -55,6 +90,7 @@ void kvm_riscv_vcpu_aia_sync_interrupts(struct kvm_vcpu *vcpu)

bool kvm_riscv_vcpu_aia_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
{
+ int hgei;
unsigned long seip;

if (!kvm_riscv_aia_available())
@@ -72,6 +108,10 @@ bool kvm_riscv_vcpu_aia_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
if (!kvm_riscv_aia_initialized(vcpu->kvm) || !seip)
return false;

+ hgei = aia_find_hgei(vcpu);
+ if (hgei > 0)
+ return (csr_read(CSR_HGEIP) & BIT(hgei)) ? true : false;
+
return false;
}

@@ -343,6 +383,144 @@ int kvm_riscv_vcpu_aia_rmw_ireg(struct kvm_vcpu *vcpu, unsigned int csr_num,
return KVM_INSN_EXIT_TO_USER_SPACE;
}

+int kvm_riscv_aia_alloc_hgei(int cpu, struct kvm_vcpu *owner,
+ void __iomem **hgei_va, phys_addr_t *hgei_pa)
+{
+ int ret = -ENOENT;
+ unsigned long flags;
+ struct aia_hgei_control *hgctrl = per_cpu_ptr(&aia_hgei, cpu);
+
+ if (!kvm_riscv_aia_available())
+ return -ENODEV;
+ if (!hgctrl)
+ return -ENODEV;
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+
+ if (hgctrl->free_bitmap) {
+ ret = __ffs(hgctrl->free_bitmap);
+ hgctrl->free_bitmap &= ~BIT(ret);
+ hgctrl->owners[ret] = owner;
+ }
+
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
+
+ /* TODO: To be updated later by AIA in-kernel irqchip support */
+ if (hgei_va)
+ *hgei_va = NULL;
+ if (hgei_pa)
+ *hgei_pa = 0;
+
+ return ret;
+}
+
+void kvm_riscv_aia_free_hgei(int cpu, int hgei)
+{
+ unsigned long flags;
+ struct aia_hgei_control *hgctrl = per_cpu_ptr(&aia_hgei, cpu);
+
+ if (!kvm_riscv_aia_available() || !hgctrl)
+ return;
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+
+ if (hgei > 0 && hgei <= kvm_riscv_aia_nr_hgei) {
+ if (!(hgctrl->free_bitmap & BIT(hgei))) {
+ hgctrl->free_bitmap |= BIT(hgei);
+ hgctrl->owners[hgei] = NULL;
+ }
+ }
+
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
+}
+
+void kvm_riscv_aia_wakeon_hgei(struct kvm_vcpu *owner, bool enable)
+{
+ int hgei;
+
+ if (!kvm_riscv_aia_available())
+ return;
+
+ hgei = aia_find_hgei(owner);
+ if (hgei > 0) {
+ if (enable)
+ csr_set(CSR_HGEIE, BIT(hgei));
+ else
+ csr_clear(CSR_HGEIE, BIT(hgei));
+ }
+}
+
+static irqreturn_t hgei_interrupt(int irq, void *dev_id)
+{
+ int i;
+ unsigned long hgei_mask, flags;
+ struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
+
+ hgei_mask = csr_read(CSR_HGEIP) & csr_read(CSR_HGEIE);
+ csr_clear(CSR_HGEIE, hgei_mask);
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+
+ for_each_set_bit(i, &hgei_mask, BITS_PER_LONG) {
+ if (hgctrl->owners[i])
+ kvm_vcpu_kick(hgctrl->owners[i]);
+ }
+
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
+
+ return IRQ_HANDLED;
+}
+
+static int aia_hgei_init(void)
+{
+ int cpu, rc;
+ struct irq_domain *domain;
+ struct aia_hgei_control *hgctrl;
+
+ /* 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;
+ }
+
+ /* Find INTC irq domain */
+ domain = irq_find_matching_fwnode(riscv_get_intc_hwnode(),
+ DOMAIN_BUS_ANY);
+ if (!domain) {
+ kvm_err("unable to find INTC domain\n");
+ return -ENOENT;
+ }
+
+ /* Map per-CPU SGEI interrupt from INTC domain */
+ hgei_parent_irq = irq_create_mapping(domain, IRQ_S_GEXT);
+ if (!hgei_parent_irq) {
+ kvm_err("unable to map SGEI IRQ\n");
+ return -ENOMEM;
+ }
+
+ /* Request per-CPU SGEI interrupt */
+ rc = request_percpu_irq(hgei_parent_irq, hgei_interrupt,
+ "riscv-kvm", &aia_hgei);
+ if (rc) {
+ kvm_err("failed to request SGEI IRQ\n");
+ return rc;
+ }
+
+ return 0;
+}
+
+static void aia_hgei_exit(void)
+{
+ /* Free per-CPU SGEI interrupt */
+ free_percpu_irq(hgei_parent_irq, &aia_hgei);
+}
+
void kvm_riscv_aia_enable(void)
{
if (!kvm_riscv_aia_available())
@@ -357,21 +535,79 @@ void kvm_riscv_aia_enable(void)
csr_write(CSR_HVIPRIO1H, 0x0);
csr_write(CSR_HVIPRIO2H, 0x0);
#endif
+
+ /* Enable per-CPU SGEI interrupt */
+ enable_percpu_irq(hgei_parent_irq,
+ irq_get_trigger_type(hgei_parent_irq));
+ csr_set(CSR_HIE, BIT(IRQ_S_GEXT));
}

void kvm_riscv_aia_disable(void)
{
+ int i;
+ unsigned long flags;
+ struct kvm_vcpu *vcpu;
+ struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
+
if (!kvm_riscv_aia_available())
return;

+ /* Disable per-CPU SGEI interrupt */
+ csr_clear(CSR_HIE, BIT(IRQ_S_GEXT));
+ disable_percpu_irq(hgei_parent_irq);
+
aia_set_hvictl(false);
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+
+ for (i = 0; i <= kvm_riscv_aia_nr_hgei; i++) {
+ vcpu = hgctrl->owners[i];
+ if (!vcpu)
+ continue;
+
+ /*
+ * We release hgctrl->lock before notifying IMSIC
+ * so that we don't have lock ordering issues.
+ */
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
+
+ /* Notify IMSIC */
+ kvm_riscv_vcpu_aia_imsic_release(vcpu);
+
+ /*
+ * Wakeup VCPU if it was blocked so that it can
+ * run on other HARTs
+ */
+ if (csr_read(CSR_HGEIE) & BIT(i)) {
+ csr_clear(CSR_HGEIE, BIT(i));
+ kvm_vcpu_kick(vcpu);
+ }
+
+ raw_spin_lock_irqsave(&hgctrl->lock, flags);
+ }
+
+ raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
}

int kvm_riscv_aia_init(void)
{
+ int rc;
+
if (!riscv_isa_extension_available(NULL, SxAIA))
return -ENODEV;

+ /* 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--;
+
+ /* Initialize guest external interrupt line management */
+ rc = aia_hgei_init();
+ if (rc)
+ return rc;
+
/* Enable KVM AIA support */
static_branch_enable(&kvm_riscv_aia_available);

@@ -380,4 +616,9 @@ int kvm_riscv_aia_init(void)

void kvm_riscv_aia_exit(void)
{
+ if (!kvm_riscv_aia_available())
+ return;
+
+ /* Cleanup the HGEI state */
+ aia_hgei_exit();
}
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 6396352b4e4d..b0b46f48f31e 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -116,7 +116,8 @@ 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\n");
+ kvm_info("AIA available with %d guest external interrupts\n",
+ kvm_riscv_aia_nr_hgei);

rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
if (rc) {
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 30acf3ebdc3d..eace51dd896f 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -249,10 +249,12 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
{
+ kvm_riscv_aia_wakeon_hgei(vcpu, true);
}

void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
{
+ kvm_riscv_aia_wakeon_hgei(vcpu, false);
}

int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
--
2.34.1