Re: [PATCH v2] LoongArch: KVM: INTC: Add IOCSR MISC register emulation

[Bibo Mao <maobibo@xxxxxxxxxxx>]

On 2025/7/1 下午5:20, Huacai Chen wrote:
> On Mon, Jun 30, 2025 at 4:44 PM Bibo Mao <maobibo@xxxxxxxxxxx> 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@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > > > ---
> > > > 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().

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