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Date: Mon, 6 May 2024 09:49:42 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <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
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.
> +
> + 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?
> +
> 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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