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Date: Mon, 6 May 2024 10:29:19 +0800
From: maobibo <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
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
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@...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.
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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