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Message-ID: <CAAhV-H41WOLU6ae-iWKLnuUtSXgq4DogEUYS49ndmERauuPgXA@mail.gmail.com>
Date: Wed, 9 Jul 2025 16:59:39 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, Xianglai Li <lixianglai@...ngson.cn>, kvm@...r.kernel.org,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] LoongArch: KVM: INTC: Add IOCSR MISC register emulation
On Tue, Jul 1, 2025 at 7:40 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>
>
>
> On 2025/7/1 下午5:20, Huacai Chen wrote:
> > On Mon, Jun 30, 2025 at 4:44 PM Bibo Mao <maobibo@...ngson.cn> wrote:
> >>
> >>
> >>
> >> On 2025/6/30 下午4:04, Huacai Chen wrote:
> >>> Hi, Bibo,
> >>>
> >>> On Thu, Jun 19, 2025 at 3:15 PM Bibo Mao <maobibo@...ngson.cn> wrote:
> >>>>
> >>>> IOCSR MISC register 0x420 controlls some features of eiointc, such as
> >>>> BIT 48 enables eiointc and BIT 49 set interrupt encoding mode.
> >>>>
> >>>> When kernel irqchip is set, IOCSR MISC register should be emulated in
> >>>> kernel also. Here add IOCSR MISC register emulation in kernel side.
> >>>>
> >>>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> >>>> ---
> >>>> v1 ... v2:
> >>>> 1. Add separate file arch/loongarch/kvm/intc/misc.c for IOCSR MISC
> >>>> register 0x420 emulation, since it controls feature about AVEC
> >>>> irqchip also.
> >>> I found we can decouple the misc register and EIOINTC in addition:
> >>> 1, Move misc.c out of intc directory;
> >>> 2, Call kvm_loongarch_create_misc() in kvm_arch_init_vm();
> >>> 3, Call kvm_loongarch_destroy_misc() in kvm_arch_destroy_vm();
> >>> 4, Then maybe misc_created can be removed.
> >> Now irqchip in kernel is optional, the same with misc register. Misc
> >> register will be emulated in user VMM if kernel-irqchip option is off.
> >>
> >> There is no way to detect kernel-irqchip option when function
> >> kvm_arch_init_vm() is called, and kvm_loongarch_create_misc() needs be
> >> dynamically called from ioctl command.
> > Can we use kvm_arch_irqchip_in_kernel() to detect?
> No, it can not be used. kvm_arch_irqchip_in_kernel() is usable only when
> irqchip is created in kernel, however kvm_arch_init_vm() is called when
> VM is created.
>
> VM is created always before kernel irqchip is created. So
> kvm_arch_irqchip_in_kernel() will return false if it is called in
> kvm_arch_init_vm().
What will happen if call kvm_loongarch_create_misc() in
kvm_arch_init_vm() unconditionally?
Huacai
>
> Regards
> Bibo Mao
> >
> >
> > Huacai
> >
> >>
> >> Regards
> >> Bibo Mao
> >>>
> >>> At last you can make this patch and others from another series to be a
> >>> new series.
> >>>
> >>>
> >>> Huacai
> >>>
> >>>>
> >>>> 2. Define macro MISC_BASE as LOONGARCH_IOCSR_MISC_FUNC rather than
> >>>> hard coded 0x420
> >>>> ---
> >>>> arch/loongarch/include/asm/kvm_eiointc.h | 2 +
> >>>> arch/loongarch/include/asm/kvm_host.h | 2 +
> >>>> arch/loongarch/include/asm/kvm_misc.h | 17 +++
> >>>> arch/loongarch/include/asm/loongarch.h | 1 +
> >>>> arch/loongarch/kvm/Makefile | 1 +
> >>>> arch/loongarch/kvm/intc/eiointc.c | 61 +++++++++++
> >>>> arch/loongarch/kvm/intc/misc.c | 125 +++++++++++++++++++++++
> >>>> 7 files changed, 209 insertions(+)
> >>>> create mode 100644 arch/loongarch/include/asm/kvm_misc.h
> >>>> create mode 100644 arch/loongarch/kvm/intc/misc.c
> >>>>
> >>>> diff --git a/arch/loongarch/include/asm/kvm_eiointc.h b/arch/loongarch/include/asm/kvm_eiointc.h
> >>>> index a3a40aba8acf..2d1c183f2b1b 100644
> >>>> --- a/arch/loongarch/include/asm/kvm_eiointc.h
> >>>> +++ b/arch/loongarch/include/asm/kvm_eiointc.h
> >>>> @@ -119,5 +119,7 @@ struct loongarch_eiointc {
> >>>>
> >>>> int kvm_loongarch_register_eiointc_device(void);
> >>>> void eiointc_set_irq(struct loongarch_eiointc *s, int irq, int level);
> >>>> +int kvm_eiointc_get_status(struct kvm_vcpu *vcpu, unsigned long *value);
> >>>> +int kvm_eiointc_update_status(struct kvm_vcpu *vcpu, unsigned long value, unsigned long mask);
> >>>>
> >>>> #endif /* __ASM_KVM_EIOINTC_H */
> >>>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> >>>> index a3c4cc46c892..f463ec52d86c 100644
> >>>> --- a/arch/loongarch/include/asm/kvm_host.h
> >>>> +++ b/arch/loongarch/include/asm/kvm_host.h
> >>>> @@ -132,6 +132,8 @@ struct kvm_arch {
> >>>> struct loongarch_ipi *ipi;
> >>>> struct loongarch_eiointc *eiointc;
> >>>> struct loongarch_pch_pic *pch_pic;
> >>>> + struct kvm_io_device misc;
> >>>> + bool misc_created;
> >>>> };
> >>>>
> >>>> #define CSR_MAX_NUMS 0x800
> >>>> diff --git a/arch/loongarch/include/asm/kvm_misc.h b/arch/loongarch/include/asm/kvm_misc.h
> >>>> new file mode 100644
> >>>> index 000000000000..621e4228dea2
> >>>> --- /dev/null
> >>>> +++ b/arch/loongarch/include/asm/kvm_misc.h
> >>>> @@ -0,0 +1,17 @@
> >>>> +/* SPDX-License-Identifier: GPL-2.0 */
> >>>> +/*
> >>>> + * Copyright (C) 2025 Loongson Technology Corporation Limited
> >>>> + */
> >>>> +
> >>>> +#ifndef __ASM_KVM_MISC_H
> >>>> +#define __ASM_KVM_MISC_H
> >>>> +
> >>>> +#include <asm/loongarch.h>
> >>>> +
> >>>> +#define MISC_BASE LOONGARCH_IOCSR_MISC_FUNC
> >>>> +#define MISC_SIZE 0x8
> >>>> +
> >>>> +int kvm_loongarch_create_misc(struct kvm *kvm);
> >>>> +void kvm_loongarch_destroy_misc(struct kvm *kvm);
> >>>> +
> >>>> +#endif /* __ASM_KVM_MISC_H */
> >>>> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> >>>> index d84dac88a584..e30d330d497e 100644
> >>>> --- a/arch/loongarch/include/asm/loongarch.h
> >>>> +++ b/arch/loongarch/include/asm/loongarch.h
> >>>> @@ -1141,6 +1141,7 @@
> >>>> #define IOCSR_MISC_FUNC_SOFT_INT BIT_ULL(10)
> >>>> #define IOCSR_MISC_FUNC_TIMER_RESET BIT_ULL(21)
> >>>> #define IOCSR_MISC_FUNC_EXT_IOI_EN BIT_ULL(48)
> >>>> +#define IOCSR_MISC_FUNC_INT_ENCODE BIT_ULL(49)
> >>>> #define IOCSR_MISC_FUNC_AVEC_EN BIT_ULL(51)
> >>>>
> >>>> #define LOONGARCH_IOCSR_CPUTEMP 0x428
> >>>> diff --git a/arch/loongarch/kvm/Makefile b/arch/loongarch/kvm/Makefile
> >>>> index cb41d9265662..25fa3866613d 100644
> >>>> --- a/arch/loongarch/kvm/Makefile
> >>>> +++ b/arch/loongarch/kvm/Makefile
> >>>> @@ -18,6 +18,7 @@ kvm-y += vcpu.o
> >>>> kvm-y += vm.o
> >>>> kvm-y += intc/ipi.o
> >>>> kvm-y += intc/eiointc.o
> >>>> +kvm-y += intc/misc.o
> >>>> kvm-y += intc/pch_pic.o
> >>>> kvm-y += irqfd.o
> >>>>
> >>>> diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
> >>>> index f39929d7bf8a..87d01521e92f 100644
> >>>> --- a/arch/loongarch/kvm/intc/eiointc.c
> >>>> +++ b/arch/loongarch/kvm/intc/eiointc.c
> >>>> @@ -4,6 +4,7 @@
> >>>> */
> >>>>
> >>>> #include <asm/kvm_eiointc.h>
> >>>> +#include <asm/kvm_misc.h>
> >>>> #include <asm/kvm_vcpu.h>
> >>>> #include <linux/count_zeros.h>
> >>>>
> >>>> @@ -708,6 +709,56 @@ static const struct kvm_io_device_ops kvm_eiointc_ops = {
> >>>> .write = kvm_eiointc_write,
> >>>> };
> >>>>
> >>>> +int kvm_eiointc_get_status(struct kvm_vcpu *vcpu, unsigned long *value)
> >>>> +{
> >>>> + unsigned long data, flags;
> >>>> + struct loongarch_eiointc *eiointc = vcpu->kvm->arch.eiointc;
> >>>> +
> >>>> + if (!eiointc) {
> >>>> + kvm_err("%s: eiointc irqchip not valid!\n", __func__);
> >>>> + return -EINVAL;
> >>>> + }
> >>>> +
> >>>> + data = 0;
> >>>> + spin_lock_irqsave(&eiointc->lock, flags);
> >>>> + if (eiointc->status & BIT(EIOINTC_ENABLE))
> >>>> + data |= IOCSR_MISC_FUNC_EXT_IOI_EN;
> >>>> +
> >>>> + if (eiointc->status & BIT(EIOINTC_ENABLE_INT_ENCODE))
> >>>> + data |= IOCSR_MISC_FUNC_INT_ENCODE;
> >>>> + spin_unlock_irqrestore(&eiointc->lock, flags);
> >>>> +
> >>>> + *value = data;
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +int kvm_eiointc_update_status(struct kvm_vcpu *vcpu, unsigned long value, unsigned long mask)
> >>>> +{
> >>>> + struct loongarch_eiointc *eiointc = vcpu->kvm->arch.eiointc;
> >>>> + unsigned long old, flags;
> >>>> +
> >>>> + if (!eiointc) {
> >>>> + kvm_err("%s: eiointc irqchip not valid!\n", __func__);
> >>>> + return -EINVAL;
> >>>> + }
> >>>> +
> >>>> + old = 0;
> >>>> + spin_lock_irqsave(&eiointc->lock, flags);
> >>>> + if (eiointc->status & BIT(EIOINTC_ENABLE))
> >>>> + old |= IOCSR_MISC_FUNC_EXT_IOI_EN;
> >>>> + if (eiointc->status & BIT(EIOINTC_ENABLE_INT_ENCODE))
> >>>> + old |= IOCSR_MISC_FUNC_INT_ENCODE;
> >>>> +
> >>>> + value |= (old & ~mask);
> >>>> + eiointc->status &= ~(BIT(EIOINTC_ENABLE_INT_ENCODE) | BIT(EIOINTC_ENABLE));
> >>>> + if (value & IOCSR_MISC_FUNC_INT_ENCODE)
> >>>> + eiointc->status |= BIT(EIOINTC_ENABLE_INT_ENCODE);
> >>>> + if (value & IOCSR_MISC_FUNC_EXT_IOI_EN)
> >>>> + eiointc->status |= BIT(EIOINTC_ENABLE);
> >>>> + spin_unlock_irqrestore(&eiointc->lock, flags);
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> static int kvm_eiointc_virt_read(struct kvm_vcpu *vcpu,
> >>>> struct kvm_io_device *dev,
> >>>> gpa_t addr, int len, void *val)
> >>>> @@ -993,6 +1044,15 @@ static int kvm_eiointc_create(struct kvm_device *dev, u32 type)
> >>>> kfree(s);
> >>>> return ret;
> >>>> }
> >>>> +
> >>>> + ret = kvm_loongarch_create_misc(kvm);
> >>>> + if (ret < 0) {
> >>>> + kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &s->device);
> >>>> + kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &s->device_vext);
> >>>> + kfree(s);
> >>>> + return ret;
> >>>> + }
> >>>> +
> >>>> kvm->arch.eiointc = s;
> >>>>
> >>>> return 0;
> >>>> @@ -1010,6 +1070,7 @@ static void kvm_eiointc_destroy(struct kvm_device *dev)
> >>>> eiointc = kvm->arch.eiointc;
> >>>> kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &eiointc->device);
> >>>> kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, &eiointc->device_vext);
> >>>> + kvm_loongarch_destroy_misc(kvm);
> >>>> kfree(eiointc);
> >>>> }
> >>>>
> >>>> diff --git a/arch/loongarch/kvm/intc/misc.c b/arch/loongarch/kvm/intc/misc.c
> >>>> new file mode 100644
> >>>> index 000000000000..edee66afa36e
> >>>> --- /dev/null
> >>>> +++ b/arch/loongarch/kvm/intc/misc.c
> >>>> @@ -0,0 +1,125 @@
> >>>> +// SPDX-License-Identifier: GPL-2.0
> >>>> +/*
> >>>> + * Copyright (C) 2025 Loongson Technology Corporation Limited
> >>>> + */
> >>>> +#include <asm/kvm_vcpu.h>
> >>>> +#include <asm/kvm_eiointc.h>
> >>>> +#include <asm/kvm_misc.h>
> >>>> +
> >>>> +static int kvm_misc_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> >>>> + gpa_t addr, int len, void *val)
> >>>> +{
> >>>> + unsigned long data;
> >>>> + unsigned int ret;
> >>>> +
> >>>> + addr -= MISC_BASE;
> >>>> + if (addr & (len - 1)) {
> >>>> + kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
> >>>> + return -EINVAL;
> >>>> + }
> >>>> +
> >>>> + ret = kvm_eiointc_get_status(vcpu, &data);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + data = data >> ((addr & 7) * 8);
> >>>> + switch (len) {
> >>>> + case 1:
> >>>> + *(unsigned char *)val = (unsigned char)data;
> >>>> + break;
> >>>> +
> >>>> + case 2:
> >>>> + *(unsigned short *)val = (unsigned short)data;
> >>>> + break;
> >>>> +
> >>>> + case 4:
> >>>> + *(unsigned int *)val = (unsigned int)data;
> >>>> + break;
> >>>> +
> >>>> + default:
> >>>> + *(unsigned long *)val = data;
> >>>> + break;
> >>>> + }
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +static int kvm_misc_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> >>>> + gpa_t addr, int len, const void *val)
> >>>> +{
> >>>> + unsigned long data, mask;
> >>>> + unsigned int shift;
> >>>> +
> >>>> + addr -= MISC_BASE;
> >>>> + if (addr & (len - 1)) {
> >>>> + kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
> >>>> + return -EINVAL;
> >>>> + }
> >>>> +
> >>>> + shift = (addr & 7) * 8;
> >>>> + switch (len) {
> >>>> + case 1:
> >>>> + data = *(unsigned char *)val;
> >>>> + mask = 0xFF;
> >>>> + mask = mask << shift;
> >>>> + data = data << shift;
> >>>> + break;
> >>>> +
> >>>> + case 2:
> >>>> + data = *(unsigned short *)val;
> >>>> + mask = 0xFFFF;
> >>>> + mask = mask << shift;
> >>>> + data = data << shift;
> >>>> + break;
> >>>> +
> >>>> + case 4:
> >>>> + data = *(unsigned int *)val;
> >>>> + mask = UINT_MAX;
> >>>> + mask = mask << shift;
> >>>> + data = data << shift;
> >>>> + break;
> >>>> +
> >>>> + default:
> >>>> + data = *(unsigned long *)val;
> >>>> + mask = ULONG_MAX;
> >>>> + mask = mask << shift;
> >>>> + data = data << shift;
> >>>> + break;
> >>>> + }
> >>>> +
> >>>> + return kvm_eiointc_update_status(vcpu, data, mask);
> >>>> +}
> >>>> +
> >>>> +static const struct kvm_io_device_ops kvm_misc_ops = {
> >>>> + .read = kvm_misc_read,
> >>>> + .write = kvm_misc_write,
> >>>> +};
> >>>> +
> >>>> +int kvm_loongarch_create_misc(struct kvm *kvm)
> >>>> +{
> >>>> + struct kvm_io_device *device;
> >>>> + int ret;
> >>>> +
> >>>> + if (kvm->arch.misc_created)
> >>>> + return 0;
> >>>> +
> >>>> + device = &kvm->arch.misc;
> >>>> + kvm_iodevice_init(device, &kvm_misc_ops);
> >>>> + ret = kvm_io_bus_register_dev(kvm, KVM_IOCSR_BUS, MISC_BASE, MISC_SIZE, device);
> >>>> + if (ret < 0)
> >>>> + return ret;
> >>>> +
> >>>> + kvm->arch.misc_created = true;
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +void kvm_loongarch_destroy_misc(struct kvm *kvm)
> >>>> +{
> >>>> + struct kvm_io_device *device;
> >>>> +
> >>>> + if (kvm->arch.misc_created) {
> >>>> + device = &kvm->arch.misc;
> >>>> + kvm_io_bus_unregister_dev(kvm, KVM_IOCSR_BUS, device);
> >>>> + kvm->arch.misc_created = false;
> >>>> + }
> >>>> +}
> >>>>
> >>>> base-commit: 52da431bf03b5506203bca27fe14a97895c80faf
> >>>> --
> >>>> 2.39.3
> >>>>
> >>
>
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