* [PATCH v2] riscv: KVM: Add hart-to-vCPU mapping for faster MSI injection
@ 2026-10-29 8:24 BillXiang
2026-10-29 9:15 ` Nutty.Liu
0 siblings, 1 reply; 3+ messages in thread
From: BillXiang @ 2026-10-29 8:24 UTC (permalink / raw)
To: anup
Cc: atish.patra, pjw, palmer, aou, alex, kvm, kvm-riscv, linux-riscv,
linux-kernel, xiangwencheng
Replace linear searches over all vCPUs in MSI injection paths with a
hart_index -> vCPU xarray lookup table. This avoids O(n) scans on
every injected interrupt and improves performance when the number of
vCPUs is large.
Both kvm_riscv_aia_inject_msi_by_id() and kvm_riscv_aia_inject_msi()
now use the table instead of iterating over the vCPU list.
Signed-off-by: BillXiang <xiangwencheng@lanxincomputing.com>
Changes in v2:
- Use xarray instead of normal array to handle incontiguous hart_index.
- Link to v1:
https://lore.kernel.org/kvm-riscv/20260730093614.983508-1-xiangwencheng@lanxincomputing.com/
---
arch/riscv/include/asm/kvm_aia.h | 3 ++
arch/riscv/kvm/aia_device.c | 50 +++++++++++++++++---------------
2 files changed, 30 insertions(+), 23 deletions(-)
diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/asm/kvm_aia.h
index ab03f853e507..3b075f18e1d6 100644
--- a/arch/riscv/include/asm/kvm_aia.h
+++ b/arch/riscv/include/asm/kvm_aia.h
@@ -12,6 +12,7 @@
#include <linux/jump_label.h>
#include <linux/kvm_types.h>
+#include <linux/xarray.h>
#include <asm/csr.h>
struct kvm_aia {
@@ -47,6 +48,8 @@ struct kvm_aia {
/* Internal state of APLIC */
void *aplic_state;
+
+ struct xarray hart_to_vcpu;
};
struct kvm_vcpu_aia_csr {
diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c
index efc7c0bcfba9..a415a8c10967 100644
--- a/arch/riscv/kvm/aia_device.c
+++ b/arch/riscv/kvm/aia_device.c
@@ -259,6 +259,8 @@ static int aia_init(struct kvm *kvm)
if (ret)
return ret;
+ xa_init(&aia->hart_to_vcpu);
+
/* Iterate over each VCPU */
kvm_for_each_vcpu(idx, vcpu, kvm) {
vaia = &vcpu->arch.aia_context;
@@ -280,6 +282,11 @@ static int aia_init(struct kvm *kvm)
/* Update HART index of the IMSIC based on IMSIC base */
vaia->hart_index = aia_imsic_hart_index(aia,
vaia->imsic_addr);
+
+ ret = xa_insert(&aia->hart_to_vcpu, vaia->hart_index, vcpu, GFP_KERNEL);
+ if (ret) {
+ goto fail_cleanup_imsics;
+ }
/* Initialize IMSIC for this VCPU */
ret = kvm_riscv_vcpu_aia_imsic_init(vcpu);
@@ -299,6 +306,7 @@ static int aia_init(struct kvm *kvm)
continue;
kvm_riscv_vcpu_aia_imsic_cleanup(vcpu);
}
+ xa_destroy(&aia->hart_to_vcpu);
kvm_riscv_aia_aplic_cleanup(kvm);
return ret;
}
@@ -557,30 +565,25 @@ void kvm_riscv_vcpu_aia_deinit(struct kvm_vcpu *vcpu)
int kvm_riscv_aia_inject_msi_by_id(struct kvm *kvm, u32 hart_index,
u32 guest_index, u32 iid)
{
- unsigned long idx;
struct kvm_vcpu *vcpu;
+ struct kvm_aia *aia = &kvm->arch.aia;
/* Proceed only if AIA was initialized successfully */
if (!kvm_riscv_aia_initialized(kvm))
return -EBUSY;
- /* Inject MSI to matching VCPU */
- kvm_for_each_vcpu(idx, vcpu, kvm) {
- if (vcpu->arch.aia_context.hart_index == hart_index)
- return kvm_riscv_vcpu_aia_imsic_inject(vcpu,
- guest_index,
- 0, iid);
- }
-
- return 0;
+ vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
+ if (!vcpu)
+ return 0;
+
+ return kvm_riscv_vcpu_aia_imsic_inject(vcpu, guest_index, 0, iid);
}
int kvm_riscv_aia_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
{
gpa_t tppn, ippn;
- unsigned long idx;
struct kvm_vcpu *vcpu;
- u32 g, toff, iid = msi->data;
+ u32 g, toff, iid = msi->data, hart_index;
struct kvm_aia *aia = &kvm->arch.aia;
gpa_t target = (((gpa_t)msi->address_hi) << 32) | msi->address_lo;
@@ -595,18 +598,16 @@ int kvm_riscv_aia_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
g = tppn & (BIT(aia->nr_guest_bits) - 1);
tppn &= ~((gpa_t)(BIT(aia->nr_guest_bits) - 1));
- /* Inject MSI to matching VCPU */
- kvm_for_each_vcpu(idx, vcpu, kvm) {
- ippn = vcpu->arch.aia_context.imsic_addr >>
- IMSIC_MMIO_PAGE_SHIFT;
- if (ippn == tppn) {
- toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
- return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g,
- toff, iid);
- }
- }
+ hart_index = aia_imsic_hart_index(aia, target);
+ vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
+ if (!vcpu)
+ return 0;
- return 0;
+ ippn = vcpu->arch.aia_context.imsic_addr >> IMSIC_MMIO_PAGE_SHIFT;
+ if (ippn != tppn)
+ return 0;
+ toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
+ return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g, toff, iid);
}
int kvm_riscv_aia_inject_irq(struct kvm *kvm, unsigned int irq, bool level)
@@ -647,9 +648,12 @@ void kvm_riscv_aia_init_vm(struct kvm *kvm)
void kvm_riscv_aia_destroy_vm(struct kvm *kvm)
{
+ struct kvm_aia *aia = &kvm->arch.aia;
/* Proceed only if AIA was initialized successfully */
if (!kvm_riscv_aia_initialized(kvm))
return;
+
+ xa_destroy(&aia->hart_to_vcpu);
/* Cleanup APLIC context */
kvm_riscv_aia_aplic_cleanup(kvm);
--
2.53.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] riscv: KVM: Add hart-to-vCPU mapping for faster MSI injection
2026-10-29 8:24 [PATCH v2] riscv: KVM: Add hart-to-vCPU mapping for faster MSI injection BillXiang
@ 2026-10-29 9:15 ` Nutty.Liu
2026-10-29 9:35 ` BillXiang
0 siblings, 1 reply; 3+ messages in thread
From: Nutty.Liu @ 2026-10-29 9:15 UTC (permalink / raw)
To: BillXiang, anup
Cc: atish.patra, pjw, palmer, aou, alex, kvm, kvm-riscv, linux-riscv,
linux-kernel
On 10/29/2026 4:24 PM, BillXiang wrote:
> Replace linear searches over all vCPUs in MSI injection paths with a
> hart_index -> vCPU xarray lookup table. This avoids O(n) scans on
> every injected interrupt and improves performance when the number of
> vCPUs is large.
>
> Both kvm_riscv_aia_inject_msi_by_id() and kvm_riscv_aia_inject_msi()
> now use the table instead of iterating over the vCPU list.
>
> Signed-off-by: BillXiang <xiangwencheng@lanxincomputing.com>
> Changes in v2:
Hi Bill,
The change log should be under the tear line.
> - Use xarray instead of normal array to handle incontiguous hart_index.
> - Link to v1:
> https://lore.kernel.org/kvm-riscv/20260730093614.983508-1-xiangwencheng@lanxincomputing.com/
> ---
> arch/riscv/include/asm/kvm_aia.h | 3 ++
> arch/riscv/kvm/aia_device.c | 50 +++++++++++++++++---------------
> 2 files changed, 30 insertions(+), 23 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/asm/kvm_aia.h
> index ab03f853e507..3b075f18e1d6 100644
> --- a/arch/riscv/include/asm/kvm_aia.h
> +++ b/arch/riscv/include/asm/kvm_aia.h
> @@ -12,6 +12,7 @@
>
> #include <linux/jump_label.h>
> #include <linux/kvm_types.h>
> +#include <linux/xarray.h>
> #include <asm/csr.h>
>
> struct kvm_aia {
> @@ -47,6 +48,8 @@ struct kvm_aia {
>
> /* Internal state of APLIC */
> void *aplic_state;
> +
> + struct xarray hart_to_vcpu;
> };
>
> struct kvm_vcpu_aia_csr {
> diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c
> index efc7c0bcfba9..a415a8c10967 100644
> --- a/arch/riscv/kvm/aia_device.c
> +++ b/arch/riscv/kvm/aia_device.c
> @@ -259,6 +259,8 @@ static int aia_init(struct kvm *kvm)
> if (ret)
> return ret;
>
> + xa_init(&aia->hart_to_vcpu);
> +
> /* Iterate over each VCPU */
> kvm_for_each_vcpu(idx, vcpu, kvm) {
> vaia = &vcpu->arch.aia_context;
> @@ -280,6 +282,11 @@ static int aia_init(struct kvm *kvm)
> /* Update HART index of the IMSIC based on IMSIC base */
> vaia->hart_index = aia_imsic_hart_index(aia,
> vaia->imsic_addr);
> +
> + ret = xa_insert(&aia->hart_to_vcpu, vaia->hart_index, vcpu, GFP_KERNEL);
> + if (ret) {
> + goto fail_cleanup_imsics;
> + }
>
> /* Initialize IMSIC for this VCPU */
> ret = kvm_riscv_vcpu_aia_imsic_init(vcpu);
> @@ -299,6 +306,7 @@ static int aia_init(struct kvm *kvm)
> continue;
> kvm_riscv_vcpu_aia_imsic_cleanup(vcpu);
> }
> + xa_destroy(&aia->hart_to_vcpu);
> kvm_riscv_aia_aplic_cleanup(kvm);
> return ret;
> }
> @@ -557,30 +565,25 @@ void kvm_riscv_vcpu_aia_deinit(struct kvm_vcpu *vcpu)
> int kvm_riscv_aia_inject_msi_by_id(struct kvm *kvm, u32 hart_index,
> u32 guest_index, u32 iid)
> {
> - unsigned long idx;
> struct kvm_vcpu *vcpu;
> + struct kvm_aia *aia = &kvm->arch.aia;
>
> /* Proceed only if AIA was initialized successfully */
> if (!kvm_riscv_aia_initialized(kvm))
> return -EBUSY;
>
> - /* Inject MSI to matching VCPU */
> - kvm_for_each_vcpu(idx, vcpu, kvm) {
> - if (vcpu->arch.aia_context.hart_index == hart_index)
> - return kvm_riscv_vcpu_aia_imsic_inject(vcpu,
> - guest_index,
> - 0, iid);
> - }
> -
> - return 0;
> + vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
> + if (!vcpu)
> + return 0;
> +
> + return kvm_riscv_vcpu_aia_imsic_inject(vcpu, guest_index, 0, iid);
> }
>
> int kvm_riscv_aia_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
> {
> gpa_t tppn, ippn;
> - unsigned long idx;
> struct kvm_vcpu *vcpu;
> - u32 g, toff, iid = msi->data;
> + u32 g, toff, iid = msi->data, hart_index;
> struct kvm_aia *aia = &kvm->arch.aia;
> gpa_t target = (((gpa_t)msi->address_hi) << 32) | msi->address_lo;
>
> @@ -595,18 +598,16 @@ int kvm_riscv_aia_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
> g = tppn & (BIT(aia->nr_guest_bits) - 1);
> tppn &= ~((gpa_t)(BIT(aia->nr_guest_bits) - 1));
>
> - /* Inject MSI to matching VCPU */
> - kvm_for_each_vcpu(idx, vcpu, kvm) {
> - ippn = vcpu->arch.aia_context.imsic_addr >>
> - IMSIC_MMIO_PAGE_SHIFT;
> - if (ippn == tppn) {
> - toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
> - return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g,
> - toff, iid);
> - }
> - }
> + hart_index = aia_imsic_hart_index(aia, target);
> + vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
> + if (!vcpu)
> + return 0;
>
> - return 0;
> + ippn = vcpu->arch.aia_context.imsic_addr >> IMSIC_MMIO_PAGE_SHIFT;
> + if (ippn != tppn)
> + return 0;
> + toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
> + return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g, toff, iid);
> }
>
> int kvm_riscv_aia_inject_irq(struct kvm *kvm, unsigned int irq, bool level)
> @@ -647,9 +648,12 @@ void kvm_riscv_aia_init_vm(struct kvm *kvm)
>
> void kvm_riscv_aia_destroy_vm(struct kvm *kvm)
> {
> + struct kvm_aia *aia = &kvm->arch.aia;
> /* Proceed only if AIA was initialized successfully */
> if (!kvm_riscv_aia_initialized(kvm))
> return;
> +
> + xa_destroy(&aia->hart_to_vcpu);
>
> /* Cleanup APLIC context */
> kvm_riscv_aia_aplic_cleanup(kvm);
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] riscv: KVM: Add hart-to-vCPU mapping for faster MSI injection
2026-10-29 9:15 ` Nutty.Liu
@ 2026-10-29 9:35 ` BillXiang
0 siblings, 0 replies; 3+ messages in thread
From: BillXiang @ 2026-10-29 9:35 UTC (permalink / raw)
To: Nutty.Liu, anup
Cc: atish.patra, pjw, palmer, aou, alex, kvm, kvm-riscv, linux-riscv,
linux-kernel
On 10/29/2026 5:15 PM, Nutty.Liu wrote:
>
> On 10/29/2026 4:24 PM, BillXiang wrote:
>> Replace linear searches over all vCPUs in MSI injection paths with a
>> hart_index -> vCPU xarray lookup table. This avoids O(n) scans on
>> every injected interrupt and improves performance when the number of
>> vCPUs is large.
>>
>> Both kvm_riscv_aia_inject_msi_by_id() and kvm_riscv_aia_inject_msi()
>> now use the table instead of iterating over the vCPU list.
>>
>> Signed-off-by: BillXiang <xiangwencheng@lanxincomputing.com>
>> Changes in v2:
> Hi Bill,
>
> The change log should be under the tear line.
Thanks for the reminder.
>> - Use xarray instead of normal array to handle incontiguous hart_index.
>> - Link to v1:
>> https://lore.kernel.org/kvm-riscv/20260730093614.983508-1-
>> xiangwencheng@lanxincomputing.com/
>> ---
>> arch/riscv/include/asm/kvm_aia.h | 3 ++
>> arch/riscv/kvm/aia_device.c | 50 +++++++++++++++++---------------
>> 2 files changed, 30 insertions(+), 23 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/
>> asm/kvm_aia.h
>> index ab03f853e507..3b075f18e1d6 100644
>> --- a/arch/riscv/include/asm/kvm_aia.h
>> +++ b/arch/riscv/include/asm/kvm_aia.h
>> @@ -12,6 +12,7 @@
>> #include <linux/jump_label.h>
>> #include <linux/kvm_types.h>
>> +#include <linux/xarray.h>
>> #include <asm/csr.h>
>> struct kvm_aia {
>> @@ -47,6 +48,8 @@ struct kvm_aia {
>> /* Internal state of APLIC */
>> void *aplic_state;
>> +
>> + struct xarray hart_to_vcpu;
>> };
>> struct kvm_vcpu_aia_csr {
>> diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c
>> index efc7c0bcfba9..a415a8c10967 100644
>> --- a/arch/riscv/kvm/aia_device.c
>> +++ b/arch/riscv/kvm/aia_device.c
>> @@ -259,6 +259,8 @@ static int aia_init(struct kvm *kvm)
>> if (ret)
>> return ret;
>> + xa_init(&aia->hart_to_vcpu);
>> +
>> /* Iterate over each VCPU */
>> kvm_for_each_vcpu(idx, vcpu, kvm) {
>> vaia = &vcpu->arch.aia_context;
>> @@ -280,6 +282,11 @@ static int aia_init(struct kvm *kvm)
>> /* Update HART index of the IMSIC based on IMSIC base */
>> vaia->hart_index = aia_imsic_hart_index(aia,
>> vaia->imsic_addr);
>> +
>> + ret = xa_insert(&aia->hart_to_vcpu, vaia->hart_index, vcpu,
>> GFP_KERNEL);
>> + if (ret) {
>> + goto fail_cleanup_imsics;
>> + }
>> /* Initialize IMSIC for this VCPU */
>> ret = kvm_riscv_vcpu_aia_imsic_init(vcpu);
>> @@ -299,6 +306,7 @@ static int aia_init(struct kvm *kvm)
>> continue;
>> kvm_riscv_vcpu_aia_imsic_cleanup(vcpu);
>> }
>> + xa_destroy(&aia->hart_to_vcpu);
>> kvm_riscv_aia_aplic_cleanup(kvm);
>> return ret;
>> }
>> @@ -557,30 +565,25 @@ void kvm_riscv_vcpu_aia_deinit(struct kvm_vcpu
>> *vcpu)
>> int kvm_riscv_aia_inject_msi_by_id(struct kvm *kvm, u32 hart_index,
>> u32 guest_index, u32 iid)
>> {
>> - unsigned long idx;
>> struct kvm_vcpu *vcpu;
>> + struct kvm_aia *aia = &kvm->arch.aia;
>> /* Proceed only if AIA was initialized successfully */
>> if (!kvm_riscv_aia_initialized(kvm))
>> return -EBUSY;
>> - /* Inject MSI to matching VCPU */
>> - kvm_for_each_vcpu(idx, vcpu, kvm) {
>> - if (vcpu->arch.aia_context.hart_index == hart_index)
>> - return kvm_riscv_vcpu_aia_imsic_inject(vcpu,
>> - guest_index,
>> - 0, iid);
>> - }
>> -
>> - return 0;
>> + vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
>> + if (!vcpu)
>> + return 0;
>> +
>> + return kvm_riscv_vcpu_aia_imsic_inject(vcpu, guest_index, 0, iid);
>> }
>> int kvm_riscv_aia_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
>> {
>> gpa_t tppn, ippn;
>> - unsigned long idx;
>> struct kvm_vcpu *vcpu;
>> - u32 g, toff, iid = msi->data;
>> + u32 g, toff, iid = msi->data, hart_index;
>> struct kvm_aia *aia = &kvm->arch.aia;
>> gpa_t target = (((gpa_t)msi->address_hi) << 32) | msi->address_lo;
>> @@ -595,18 +598,16 @@ int kvm_riscv_aia_inject_msi(struct kvm *kvm,
>> struct kvm_msi *msi)
>> g = tppn & (BIT(aia->nr_guest_bits) - 1);
>> tppn &= ~((gpa_t)(BIT(aia->nr_guest_bits) - 1));
>> - /* Inject MSI to matching VCPU */
>> - kvm_for_each_vcpu(idx, vcpu, kvm) {
>> - ippn = vcpu->arch.aia_context.imsic_addr >>
>> - IMSIC_MMIO_PAGE_SHIFT;
>> - if (ippn == tppn) {
>> - toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
>> - return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g,
>> - toff, iid);
>> - }
>> - }
>> + hart_index = aia_imsic_hart_index(aia, target);
>> + vcpu = xa_load(&aia->hart_to_vcpu, hart_index);
>> + if (!vcpu)
>> + return 0;
>> - return 0;
>> + ippn = vcpu->arch.aia_context.imsic_addr >> IMSIC_MMIO_PAGE_SHIFT;
>> + if (ippn != tppn)
>> + return 0;
>> + toff = target & (IMSIC_MMIO_PAGE_SZ - 1);
>> + return kvm_riscv_vcpu_aia_imsic_inject(vcpu, g, toff, iid);
>> }
>> int kvm_riscv_aia_inject_irq(struct kvm *kvm, unsigned int irq, bool
>> level)
>> @@ -647,9 +648,12 @@ void kvm_riscv_aia_init_vm(struct kvm *kvm)
>> void kvm_riscv_aia_destroy_vm(struct kvm *kvm)
>> {
>> + struct kvm_aia *aia = &kvm->arch.aia;
>> /* Proceed only if AIA was initialized successfully */
>> if (!kvm_riscv_aia_initialized(kvm))
>> return;
>> +
>> + xa_destroy(&aia->hart_to_vcpu);
>> /* Cleanup APLIC context */
>> kvm_riscv_aia_aplic_cleanup(kvm);
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-10-29 8:24 [PATCH v2] riscv: KVM: Add hart-to-vCPU mapping for faster MSI injection BillXiang
2026-10-29 9:15 ` Nutty.Liu
2026-10-29 9:35 ` BillXiang
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