Messages in this thread | | | Subject | Re: [PATCH v8 4/6] LoongArch: KVM: Add vcpu search support from physical cpuid | From | maobibo <> | Date | Mon, 6 May 2024 10:29:19 +0800 |
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Huacai,
Many thanks for reviewing pv ipi patchset. And I reply inline.
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@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 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@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/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. Will do.
> >> + >> + 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? When VM is power-on, vcpu thread can run at the same time, so there is spinlock for kvm_set_cpuid(). And kvm_drop_cpuid() is called when vcpu is destroyed, such VM destroy or vcpu hot removed.
I think that it is impossible to send IPI to hot removed cpu, guest kernel should assure this.
Need double check whether it is possible that cpu hot-add can be in parallel with hot-removed. We can investigate and add this after LoongArch cpu hotplug is supported.
> >> + >> 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". yes, that is a problem. kvm_drop_cpuid() should be put before kfree.
Regards Bibo Mao > > 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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