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Date: Mon, 6 May 2024 16:59:36 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: maobibo <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, Juergen Gross <jgross@...e.com>,
Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev,
kvm@...r.kernel.org
Subject: Re: [PATCH v8 4/6] LoongArch: KVM: Add vcpu search support from
physical cpuid
On Mon, May 6, 2024 at 4:18 PM maobibo <maobibo@...ngson.cn> wrote:
>
>
>
> On 2024/5/6 下午3:06, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Mon, May 6, 2024 at 2:36 PM maobibo <maobibo@...ngson.cn> wrote:
> >>
> >>
> >>
> >> On 2024/5/6 上午9:49, Huacai Chen wrote:
> >>> Hi, Bibo,
> >>>
> >>> On Sun, Apr 28, 2024 at 6:05 PM Bibo Mao <maobibo@...ngson.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 vcpu
> >>>> 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 65536
> >>>> 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@...ngson.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/loongarch/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 different
> >>>> + * 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 65536
> >>>> + *
> >>>> + * Currently max CPUID is defined as 256 for KVM hypervisor, in future
> >>>> + * it will be expanded to 4096, including 16 packages at most. And 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/loongarch/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 = vcpu->arch.csr;
> >>>> + struct kvm_phyid_map *map;
> >>>> +
> >>>> + if (val >= KVM_MAX_PHYID)
> >>>> + return -EINVAL;
> >>>> +
> >>>> + cpuid = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT);
> >>>> + map = 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 != val) {
> >>>> + /*
> >>>> + * Cpuid 0 is initial value for vcpu, maybe 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_lock);
> >>>> + 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 == 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_cpuid().
In my opinion, if a vcpu with a uninitialized default physid=0, then
map->phys_map[cpuid].enabled should be 0, then code won't come here.
And if a vcpu with a real physid=0, then map->phys_map[cpuid].enabled
is 1, but we shouldn't allow it to change physid in this case.
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 != vcpu) {
> >>>> + spin_unlock(&vcpu->kvm->arch.phyid_map_lock);
> >>>> + 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 = true;
> >>>> + map->phys_map[val].vcpu = vcpu;
> >>>> + if (map->max_phyid < val)
> >>>> + map->max_phyid = 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 >= KVM_MAX_PHYID)
> >>>> + return NULL;
> >>>> +
> >>>> + map = 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 = vcpu->arch.csr;
> >>>> + struct kvm_phyid_map *map;
> >>>> +
> >>>> + map = vcpu->kvm->arch.phyid_map;
> >>>> + cpuid = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT);
> >>>> + if (cpuid >= KVM_MAX_PHYID)
> >>>> + return;
> >>>> +
> >>>> + if (map->phys_map[cpuid].enabled) {
> >>>> + map->phys_map[cpuid].vcpu = NULL;
> >>>> + map->phys_map[cpuid].enabled = 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 = 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 == 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 *vcpu)
> >>>> 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 = kvzalloc(sizeof(struct kvm_phyid_map),
> >>>> + GFP_KERNEL_ACCOUNT);
> >>>> + if (!kvm->arch.phyid_map) {
> >>>> + free_page((unsigned long)kvm->arch.pgd);
> >>>> + kvm->arch.pgd = NULL;
> >>>> + return -ENOMEM;
> >>>> + }
> >>>> +
> >>>> kvm_init_vmcs(kvm);
> >>>> kvm->arch.gpa_size = BIT(cpu_vabits - 1);
> >>>> kvm->arch.root_level = CONFIG_PGTABLE_LEVELS - 1;
> >>>> @@ -44,6 +52,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> >>>> for (i = 0; i <= kvm->arch.root_level; i++)
> >>>> kvm->arch.pte_shifts[i] = PAGE_SHIFT + i * (PAGE_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 = NULL;
> >>>> + kvm->arch.phyid_map = NULL;
> >>>> }
> >>>>
> >>>> int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >>>> --
> >>>> 2.39.3
> >>>>
> >>
>
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