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In-Reply-To: <540aa8dd-eada-1f77-0a20-38196fb5472a@loongson.cn>
From: Huacai Chen <chenhuacai@kernel.org>
Date: Mon, 6 May 2024 17:40:35 +0800
Message-ID: <CAAhV-H7o3oG2KXc2Ou0aWXTLPSNiM3evSB5Z-5dH4bLRd_P_0Q@mail.gmail.com>
Subject: Re: [PATCH v8 4/6] LoongArch: KVM: Add vcpu search support from
 physical cpuid
To: maobibo <maobibo@loongson.cn>
Cc: Tianrui Zhao <zhaotianrui@loongson.cn>, Juergen Gross <jgross@suse.com>, 
	Paolo Bonzini <pbonzini@redhat.com>, Jonathan Corbet <corbet@lwn.net>, loongarch@lists.linux.dev, 
	linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, 
	kvm@vger.kernel.org
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On Mon, May 6, 2024 at 5:35=E2=80=AFPM maobibo <maobibo@loongson.cn> wrote:
>
>
>
> On 2024/5/6 =E4=B8=8B=E5=8D=884:59, Huacai Chen wrote:
> > On Mon, May 6, 2024 at 4:18=E2=80=AFPM maobibo <maobibo@loongson.cn> wr=
ote:
> >>
> >>
> >>
> >> On 2024/5/6 =E4=B8=8B=E5=8D=883:06, Huacai Chen wrote:
> >>> Hi, Bibo,
> >>>
> >>> On Mon, May 6, 2024 at 2:36=E2=80=AFPM maobibo <maobibo@loongson.cn> =
wrote:
> >>>>
> >>>>
> >>>>
> >>>> On 2024/5/6 =E4=B8=8A=E5=8D=889:49, Huacai Chen wrote:
> >>>>> Hi, Bibo,
> >>>>>
> >>>>> On Sun, Apr 28, 2024 at 6:05=E2=80=AFPM Bibo Mao <maobibo@loongson.=
cn> wrote:
> >>>>>>
> >>>>>> Physical cpuid is used for interrupt routing for irqchips such as
> >>>>>> ipi/msi/extioi interrupt controller. And physical cpuid is stored
> >>>>>> at CSR register LOONGARCH_CSR_CPUID, it can not be changed once vc=
pu
> >>>>>> is created and physical cpuid of two vcpus cannot be the same.
> >>>>>>
> >>>>>> Different irqchips have different size declaration about physical =
cpuid,
> >>>>>> max cpuid value for CSR LOONGARCH_CSR_CPUID on 3A5000 is 512, max =
cpuid
> >>>>>> supported by IPI hardware is 1024, 256 for extioi irqchip, and 655=
36
> >>>>>> for MSI irqchip.
> >>>>>>
> >>>>>> The smallest value from all interrupt controllers is selected now,
> >>>>>> and the max cpuid size is defines as 256 by KVM which comes from
> >>>>>> extioi irqchip.
> >>>>>>
> >>>>>> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> >>>>>> ---
> >>>>>>     arch/loongarch/include/asm/kvm_host.h | 26 ++++++++
> >>>>>>     arch/loongarch/include/asm/kvm_vcpu.h |  1 +
> >>>>>>     arch/loongarch/kvm/vcpu.c             | 93 +++++++++++++++++++=
+++++++-
> >>>>>>     arch/loongarch/kvm/vm.c               | 11 ++++
> >>>>>>     4 files changed, 130 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarc=
h/include/asm/kvm_host.h
> >>>>>> index 2d62f7b0d377..3ba16ef1fe69 100644
> >>>>>> --- a/arch/loongarch/include/asm/kvm_host.h
> >>>>>> +++ b/arch/loongarch/include/asm/kvm_host.h
> >>>>>> @@ -64,6 +64,30 @@ struct kvm_world_switch {
> >>>>>>
> >>>>>>     #define MAX_PGTABLE_LEVELS     4
> >>>>>>
> >>>>>> +/*
> >>>>>> + * Physical cpu id is used for interrupt routing, there are diffe=
rent
> >>>>>> + * definitions about physical cpuid on different hardwares.
> >>>>>> + *  For LOONGARCH_CSR_CPUID register, max cpuid size if 512
> >>>>>> + *  For IPI HW, max dest CPUID size 1024
> >>>>>> + *  For extioi interrupt controller, max dest CPUID size is 256
> >>>>>> + *  For MSI interrupt controller, max supported CPUID size is 655=
36
> >>>>>> + *
> >>>>>> + * Currently max CPUID is defined as 256 for KVM hypervisor, in f=
uture
> >>>>>> + * it will be expanded to 4096, including 16 packages at most. An=
d every
> >>>>>> + * package supports at most 256 vcpus
> >>>>>> + */
> >>>>>> +#define KVM_MAX_PHYID          256
> >>>>>> +
> >>>>>> +struct kvm_phyid_info {
> >>>>>> +       struct kvm_vcpu *vcpu;
> >>>>>> +       bool            enabled;
> >>>>>> +};
> >>>>>> +
> >>>>>> +struct kvm_phyid_map {
> >>>>>> +       int max_phyid;
> >>>>>> +       struct kvm_phyid_info phys_map[KVM_MAX_PHYID];
> >>>>>> +};
> >>>>>> +
> >>>>>>     struct kvm_arch {
> >>>>>>            /* Guest physical mm */
> >>>>>>            kvm_pte_t *pgd;
> >>>>>> @@ -71,6 +95,8 @@ struct kvm_arch {
> >>>>>>            unsigned long invalid_ptes[MAX_PGTABLE_LEVELS];
> >>>>>>            unsigned int  pte_shifts[MAX_PGTABLE_LEVELS];
> >>>>>>            unsigned int  root_level;
> >>>>>> +       spinlock_t    phyid_map_lock;
> >>>>>> +       struct kvm_phyid_map  *phyid_map;
> >>>>>>
> >>>>>>            s64 time_offset;
> >>>>>>            struct kvm_context __percpu *vmcs;
> >>>>>> diff --git a/arch/loongarch/include/asm/kvm_vcpu.h b/arch/loongarc=
h/include/asm/kvm_vcpu.h
> >>>>>> index 0cb4fdb8a9b5..9f53950959da 100644
> >>>>>> --- a/arch/loongarch/include/asm/kvm_vcpu.h
> >>>>>> +++ b/arch/loongarch/include/asm/kvm_vcpu.h
> >>>>>> @@ -81,6 +81,7 @@ void kvm_save_timer(struct kvm_vcpu *vcpu);
> >>>>>>     void kvm_restore_timer(struct kvm_vcpu *vcpu);
> >>>>>>
> >>>>>>     int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm=
_interrupt *irq);
> >>>>>> +struct kvm_vcpu *kvm_get_vcpu_by_cpuid(struct kvm *kvm, int cpuid=
);
> >>>>>>
> >>>>>>     /*
> >>>>>>      * Loongarch KVM guest interrupt handling
> >>>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> >>>>>> index 3a8779065f73..b633fd28b8db 100644
> >>>>>> --- a/arch/loongarch/kvm/vcpu.c
> >>>>>> +++ b/arch/loongarch/kvm/vcpu.c
> >>>>>> @@ -274,6 +274,95 @@ static int _kvm_getcsr(struct kvm_vcpu *vcpu,=
 unsigned int id, u64 *val)
> >>>>>>            return 0;
> >>>>>>     }
> >>>>>>
> >>>>>> +static inline int kvm_set_cpuid(struct kvm_vcpu *vcpu, u64 val)
> >>>>>> +{
> >>>>>> +       int cpuid;
> >>>>>> +       struct loongarch_csrs *csr =3D vcpu->arch.csr;
> >>>>>> +       struct kvm_phyid_map  *map;
> >>>>>> +
> >>>>>> +       if (val >=3D KVM_MAX_PHYID)
> >>>>>> +               return -EINVAL;
> >>>>>> +
> >>>>>> +       cpuid =3D kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT);
> >>>>>> +       map =3D vcpu->kvm->arch.phyid_map;
> >>>>>> +       spin_lock(&vcpu->kvm->arch.phyid_map_lock);
> >>>>>> +       if (map->phys_map[cpuid].enabled) {
> >>>>>> +               /*
> >>>>>> +                * Cpuid is already set before
> >>>>>> +                * Forbid changing different cpuid at runtime
> >>>>>> +                */
> >>>>>> +               if (cpuid !=3D val) {
> >>>>>> +                       /*
> >>>>>> +                        * Cpuid 0 is initial value for vcpu, mayb=
e invalid
> >>>>>> +                        * unset value for vcpu
> >>>>>> +                        */
> >>>>>> +                       if (cpuid) {
> >>>>>> +                               spin_unlock(&vcpu->kvm->arch.phyid=
_map_lock);
> >>>>>> +                               return -EINVAL;
> >>>>>> +                       }
> >>>>>> +               } else {
> >>>>>> +                        /* Discard duplicated cpuid set */
> >>>>>> +                       spin_unlock(&vcpu->kvm->arch.phyid_map_loc=
k);
> >>>>>> +                       return 0;
> >>>>>> +               }
> >>>>>> +       }
> >>>>> I have changed the logic and comments when I apply, you can double
> >>>>> check whether it is correct.
> >>>> I checkout the latest version, the modification in function
> >>>> kvm_set_cpuid() is good for me.
> >>> Now the modified version is like this:
> >>>
> >>> + if (map->phys_map[cpuid].enabled) {
> >>> + /* Discard duplicated CPUID set operation */
> >>> + if (cpuid =3D=3D val) {
> >>> + spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
> >>> + return 0;
> >>> + }
> >>> +
> >>> + /*
> >>> + * CPUID is already set before
> >>> + * Forbid changing different CPUID at runtime
> >>> + * But CPUID 0 is the initial value for vcpu, so allow
> >>> + * changing from 0 to others
> >>> + */
> >>> + if (cpuid) {
> >>> + spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
> >>> + return -EINVAL;
> >>> + }
> >>> + }
> >>> But I still doubt whether we should allow changing from 0 to others
> >>> while map->phys_map[cpuid].enabled is 1.
> >> It is necessary since the default sw cpuid is zero :-( And we can
> >> optimize it in later, such as set INVALID cpuid in function
> >> kvm_arch_vcpu_create() and logic will be simple in function kvm_set_cp=
uid().
> > In my opinion, if a vcpu with a uninitialized default physid=3D0, then
> > map->phys_map[cpuid].enabled should be 0, then code won't come here.
> > And if a vcpu with a real physid=3D0, then map->phys_map[cpuid].enabled
> > is 1, but we shouldn't allow it to change physid in this case.
> yes, that is actually a problem.
>
> vcpu0 firstly set physid=3D0, and vcpu0 set physid=3D1 again is not allow=
ed.
> vcpu0 firstly set physid=3D0, and vcpu1 set physid=3D1 is allowed.

So can we simply drop the if (cpuid) checking? That means:
+ if (map->phys_map[cpuid].enabled) {
+ /* Discard duplicated CPUID set operation */
+ if (cpuid =3D=3D val) {
+ spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
+ return 0;
+ }
+
+ spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
+ return -EINVAL;
+ }

Huacai

>
>
> >
> > Huacai
> >
> >>
> >> Regards
> >> Bibo Mao
> >>
> >>>
> >>> Huacai
> >>>
> >>>>>
> >>>>>> +
> >>>>>> +       if (map->phys_map[val].enabled) {
> >>>>>> +               /*
> >>>>>> +                * New cpuid is already set with other vcpu
> >>>>>> +                * Forbid sharing the same cpuid between different=
 vcpus
> >>>>>> +                */
> >>>>>> +               if (map->phys_map[val].vcpu !=3D vcpu) {
> >>>>>> +                       spin_unlock(&vcpu->kvm->arch.phyid_map_loc=
k);
> >>>>>> +                       return -EINVAL;
> >>>>>> +               }
> >>>>>> +
> >>>>>> +               /* Discard duplicated cpuid set operation*/
> >>>>>> +               spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
> >>>>>> +               return 0;
> >>>>>> +       }
> >>>>>> +
> >>>>>> +       kvm_write_sw_gcsr(csr, LOONGARCH_CSR_CPUID, val);
> >>>>>> +       map->phys_map[val].enabled      =3D true;
> >>>>>> +       map->phys_map[val].vcpu         =3D vcpu;
> >>>>>> +       if (map->max_phyid < val)
> >>>>>> +               map->max_phyid =3D val;
> >>>>>> +       spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
> >>>>>> +       return 0;
> >>>>>> +}
> >>>>>> +
> >>>>>> +struct kvm_vcpu *kvm_get_vcpu_by_cpuid(struct kvm *kvm, int cpuid=
)
> >>>>>> +{
> >>>>>> +       struct kvm_phyid_map  *map;
> >>>>>> +
> >>>>>> +       if (cpuid >=3D KVM_MAX_PHYID)
> >>>>>> +               return NULL;
> >>>>>> +
> >>>>>> +       map =3D kvm->arch.phyid_map;
> >>>>>> +       if (map->phys_map[cpuid].enabled)
> >>>>>> +               return map->phys_map[cpuid].vcpu;
> >>>>>> +
> >>>>>> +       return NULL;
> >>>>>> +}
> >>>>>> +
> >>>>>> +static inline void kvm_drop_cpuid(struct kvm_vcpu *vcpu)
> >>>>>> +{
> >>>>>> +       int cpuid;
> >>>>>> +       struct loongarch_csrs *csr =3D vcpu->arch.csr;
> >>>>>> +       struct kvm_phyid_map  *map;
> >>>>>> +
> >>>>>> +       map =3D vcpu->kvm->arch.phyid_map;
> >>>>>> +       cpuid =3D kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT);
> >>>>>> +       if (cpuid >=3D KVM_MAX_PHYID)
> >>>>>> +               return;
> >>>>>> +
> >>>>>> +       if (map->phys_map[cpuid].enabled) {
> >>>>>> +               map->phys_map[cpuid].vcpu =3D NULL;
> >>>>>> +               map->phys_map[cpuid].enabled =3D false;
> >>>>>> +               kvm_write_sw_gcsr(csr, LOONGARCH_CSR_CPUID, 0);
> >>>>>> +       }
> >>>>>> +}
> >>>>> While kvm_set_cpuid() is protected by a spinlock, do kvm_drop_cpuid=
()
> >>>>> and kvm_get_vcpu_by_cpuid() also need it?
> >>>>>
> >>>> It is good to me that spinlock is added in function kvm_drop_cpuid()=
.
> >>>> And thinks for the efforts.
> >>>>
> >>>> Regards
> >>>> Bibo Mao
> >>>>>> +
> >>>>>>     static int _kvm_setcsr(struct kvm_vcpu *vcpu, unsigned int id,=
 u64 val)
> >>>>>>     {
> >>>>>>            int ret =3D 0, gintc;
> >>>>>> @@ -291,7 +380,8 @@ static int _kvm_setcsr(struct kvm_vcpu *vcpu, =
unsigned int id, u64 val)
> >>>>>>                    kvm_set_sw_gcsr(csr, LOONGARCH_CSR_ESTAT, gintc=
);
> >>>>>>
> >>>>>>                    return ret;
> >>>>>> -       }
> >>>>>> +       } else if (id =3D=3D LOONGARCH_CSR_CPUID)
> >>>>>> +               return kvm_set_cpuid(vcpu, val);
> >>>>>>
> >>>>>>            kvm_write_sw_gcsr(csr, id, val);
> >>>>>>
> >>>>>> @@ -943,6 +1033,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *v=
cpu)
> >>>>>>            hrtimer_cancel(&vcpu->arch.swtimer);
> >>>>>>            kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
> >>>>>>            kfree(vcpu->arch.csr);
> >>>>>> +       kvm_drop_cpuid(vcpu);
> >>>>> I think this line should be before the above kfree(), otherwise you
> >>>>> get a "use after free".
> >>>>>
> >>>>> Huacai
> >>>>>
> >>>>>>
> >>>>>>            /*
> >>>>>>             * If the vCPU is freed and reused as another vCPU, we =
don't want the
> >>>>>> diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
> >>>>>> index 0a37f6fa8f2d..6006a28653ad 100644
> >>>>>> --- a/arch/loongarch/kvm/vm.c
> >>>>>> +++ b/arch/loongarch/kvm/vm.c
> >>>>>> @@ -30,6 +30,14 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned =
long type)
> >>>>>>            if (!kvm->arch.pgd)
> >>>>>>                    return -ENOMEM;
> >>>>>>
> >>>>>> +       kvm->arch.phyid_map =3D kvzalloc(sizeof(struct kvm_phyid_m=
ap),
> >>>>>> +                               GFP_KERNEL_ACCOUNT);
> >>>>>> +       if (!kvm->arch.phyid_map) {
> >>>>>> +               free_page((unsigned long)kvm->arch.pgd);
> >>>>>> +               kvm->arch.pgd =3D NULL;
> >>>>>> +               return -ENOMEM;
> >>>>>> +       }
> >>>>>> +
> >>>>>>            kvm_init_vmcs(kvm);
> >>>>>>            kvm->arch.gpa_size =3D BIT(cpu_vabits - 1);
> >>>>>>            kvm->arch.root_level =3D CONFIG_PGTABLE_LEVELS - 1;
> >>>>>> @@ -44,6 +52,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned l=
ong type)
> >>>>>>            for (i =3D 0; i <=3D kvm->arch.root_level; i++)
> >>>>>>                    kvm->arch.pte_shifts[i] =3D PAGE_SHIFT + i * (P=
AGE_SHIFT - 3);
> >>>>>>
> >>>>>> +       spin_lock_init(&kvm->arch.phyid_map_lock);
> >>>>>>            return 0;
> >>>>>>     }
> >>>>>>
> >>>>>> @@ -51,7 +60,9 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
> >>>>>>     {
> >>>>>>            kvm_destroy_vcpus(kvm);
> >>>>>>            free_page((unsigned long)kvm->arch.pgd);
> >>>>>> +       kvfree(kvm->arch.phyid_map);
> >>>>>>            kvm->arch.pgd =3D NULL;
> >>>>>> +       kvm->arch.phyid_map =3D NULL;
> >>>>>>     }
> >>>>>>
> >>>>>>     int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >>>>>> --
> >>>>>> 2.39.3
> >>>>>>
> >>>>
> >>
>