RE: [PATCH RFC v5 07/12] hw/riscv: PLIC update external interrupt by KVM when kvm enabled

[Jiangyifei <jiangyifei@huawei.com>]

> -----Original Message-----
> From: Qemu-riscv
> [mailto:qemu-riscv-bounces+jiangyifei=huawei.com@nongnu.org] On Behalf Of
> Anup Patel
> Sent: Friday, April 30, 2021 12:54 PM
> To: Jiangyifei <jiangyifei@huawei.com>
> Cc: Bin Meng <bin.meng@windriver.com>; open list:RISC-V
> <qemu-riscv@nongnu.org>; Sagar Karandikar <sagark@eecs.berkeley.edu>;
> KVM General <kvm@vger.kernel.org>; libvir-list@redhat.com; Bastian
> Koppelmann <kbastian@mail.uni-paderborn.de>; Anup Patel
> <anup.patel@wdc.com>; QEMU Developers <qemu-devel@nongnu.org>;
> yinyipeng <yinyipeng1@huawei.com>; Palmer Dabbelt <palmer@dabbelt.com>;
> kvm-riscv@lists.infradead.org; Alistair Francis <Alistair.Francis@wdc.com>;
> Fanliang (EulerOS) <fanliang@huawei.com>; Wubin (H)
> <wu.wubin@huawei.com>; Zhanghailiang <zhang.zhanghailiang@huawei.com>
> Subject: Re: [PATCH RFC v5 07/12] hw/riscv: PLIC update external interrupt by
> KVM when kvm enabled
> 
> On Mon, Apr 12, 2021 at 12:24 PM Yifei Jiang <jiangyifei@huawei.com> wrote:
> >
> > Only support supervisor external interrupt currently.
> >
> > Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
> > Signed-off-by: Yipeng Yin <yinyipeng1@huawei.com>
> > ---
> >  hw/intc/sifive_plic.c    | 29 ++++++++++++++++++++---------
> >  target/riscv/kvm-stub.c  |  5 +++++
> >  target/riscv/kvm.c       | 20 ++++++++++++++++++++
> >  target/riscv/kvm_riscv.h |  1 +
> >  4 files changed, 46 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c index
> > 97a1a27a9a..2746eb7a05 100644
> > --- a/hw/intc/sifive_plic.c
> > +++ b/hw/intc/sifive_plic.c
> > @@ -31,6 +31,8 @@
> >  #include "target/riscv/cpu.h"
> >  #include "sysemu/sysemu.h"
> >  #include "migration/vmstate.h"
> > +#include "sysemu/kvm.h"
> > +#include "kvm_riscv.h"
> >
> >  #define RISCV_DEBUG_PLIC 0
> >
> > @@ -147,15 +149,24 @@ static void sifive_plic_update(SiFivePLICState *plic)
> >              continue;
> >          }
> >          int level = sifive_plic_irqs_pending(plic, addrid);
> > -        switch (mode) {
> > -        case PLICMode_M:
> > -            riscv_cpu_update_mip(RISCV_CPU(cpu), MIP_MEIP,
> BOOL_TO_MASK(level));
> > -            break;
> > -        case PLICMode_S:
> > -            riscv_cpu_update_mip(RISCV_CPU(cpu), MIP_SEIP,
> BOOL_TO_MASK(level));
> > -            break;
> > -        default:
> > -            break;
> > +        if (kvm_enabled()) {
> > +            if (mode == PLICMode_M) {
> > +                continue;
> > +            }
> > +            kvm_riscv_set_irq(RISCV_CPU(cpu), IRQ_S_EXT, level);
> > +        } else {
> > +            switch (mode) {
> > +            case PLICMode_M:
> > +                riscv_cpu_update_mip(RISCV_CPU(cpu),
> > +                                     MIP_MEIP,
> BOOL_TO_MASK(level));
> > +                break;
> > +            case PLICMode_S:
> > +                riscv_cpu_update_mip(RISCV_CPU(cpu),
> > +                                     MIP_SEIP,
> BOOL_TO_MASK(level));
> > +                break;
> > +            default:
> > +                break;
> > +            }
> 
> I am not comfortable with this patch.
> 
> This way we will endup calling kvm_riscv_set_irq() from various places in
> hw/intc and hw/riscv.
> 
> I suggest to extend riscv_cpu_update_mip() such that when kvm is enabled
> riscv_cpu_update_mip() will:
> 1) Consider only MIP_SEIP bit in "mask" parameter and all other
>     bits in "mask" parameter will be ignored probably with warning
> 2) When the MIP_SEIP bit is set in "mask" call kvm_riscv_set_irq() to change
> the IRQ state in the KVM module.
> 
> Regards,
> Anup
> 

Yes, but riscv_cpu_update_mip() in target/riscv/cpu_helper.c is used to TCG. So it is not
appropriate to adapt for KVM.

We will move riscv_cpu_update_mip() to target/riscv/cpu.c and modify it according your
advice.

Regards,
Yifei

> >          }
> >      }
> >
> > diff --git a/target/riscv/kvm-stub.c b/target/riscv/kvm-stub.c index
> > 39b96fe3f4..4e8fc31a21 100644
> > --- a/target/riscv/kvm-stub.c
> > +++ b/target/riscv/kvm-stub.c
> > @@ -23,3 +23,8 @@ void kvm_riscv_reset_vcpu(RISCVCPU *cpu)  {
> >      abort();
> >  }
> > +
> > +void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level) {
> > +    abort();
> > +}
> > diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c index
> > 79c931acb4..da63535812 100644
> > --- a/target/riscv/kvm.c
> > +++ b/target/riscv/kvm.c
> > @@ -453,6 +453,26 @@ void kvm_riscv_reset_vcpu(RISCVCPU *cpu)
> >      env->gpr[11] = cpu->env.fdt_addr;          /* a1 */
> >  }
> >
> > +void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level) {
> > +    int ret;
> > +    unsigned virq = level ? KVM_INTERRUPT_SET :
> KVM_INTERRUPT_UNSET;
> > +
> > +    if (irq != IRQ_S_EXT) {
> > +        return;
> > +    }
> > +
> > +    if (!kvm_enabled()) {
> > +        return;
> > +    }
> > +
> > +    ret = kvm_vcpu_ioctl(CPU(cpu), KVM_INTERRUPT, &virq);
> > +    if (ret < 0) {
> > +        perror("Set irq failed");
> > +        abort();
> > +    }
> > +}
> > +
> >  bool kvm_arch_cpu_check_are_resettable(void)
> >  {
> >      return true;
> > diff --git a/target/riscv/kvm_riscv.h b/target/riscv/kvm_riscv.h index
> > f38c82bf59..ed281bdce0 100644
> > --- a/target/riscv/kvm_riscv.h
> > +++ b/target/riscv/kvm_riscv.h
> > @@ -20,5 +20,6 @@
> >  #define QEMU_KVM_RISCV_H
> >
> >  void kvm_riscv_reset_vcpu(RISCVCPU *cpu);
> > +void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level);
> >
> >  #endif
> > --
> > 2.19.1
> >
> >
> > --
> > kvm-riscv mailing list
> > kvm-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kvm-riscv