Re: [PATCH kernel v2] KVM: PPC: Merge powerpc's debugfs entry content into generic entry

[hopefulle fixed my thunderbird now]

Huh, not sure anymore after reading d56f5136b0102 "KVM: let 
kvm_destroy_vm_debugfs clean up vCPU debugfs directories" which remove
debugfs_dentry from vcpu. Paolo?


On 05/09/2021 12:27, Alexey Kardashevskiy wrote:
> Please ignore this one, v3 is coming.
> 
> After I posted this, I suddenly realized that the vcpu debugfs entry
> remain until the VM exists and this does not handle vcpu
> hotunplug+hotplug (the ppc book3e did handle this). Thanks,
> 
> 
> On 04/09/2021 23:35, Alexey Kardashevskiy wrote:
>> At the moment the generic KVM code creates an "%pid-%fd" entry per a KVM
>> instance; and the PPC HV KVM creates its own at "vm%pid". The Book3E KVM
>> creates its own entry for timings.
>>
>> The problems with the PPC entries are:
>> 1. they do not allow multiple VMs in the same process (which is extremely
>> rare case mostly used by syzkaller fuzzer);
>> 2. prone to race bugs like the generic KVM code had fixed in
>> commit 85cd39af14f4 ("KVM: Do not leak memory for duplicate debugfs
>> directories").
>>
>> This defines kvm_arch_create_kvm_debugfs() similar to one for vcpus.
>>
>> This defines 2 hooks in kvmppc_ops for allowing specific KVM
>> implementations to add necessary entries. This defines handlers
>> for HV KVM and defines the Book3E debugfs vcpu helper as a handler.
>>
>> This makes use of already existing kvm_arch_create_vcpu_debugfs
>> on PPC.
>>
>> This removes no more used debugfs_dir pointers from PPC kvm_arch structs.
>>
>> Suggested-by: Fabiano Rosas <[email protected]>
>> Signed-off-by: Alexey Kardashevskiy <[email protected]>
>> ---
>> Changes:
>> v2:
>> * handled powerpc-booke
>> * s/kvm/vm/ in arch hooks
>> ---
>>    arch/powerpc/include/asm/kvm_host.h    |  7 +++---
>>    arch/powerpc/include/asm/kvm_ppc.h     |  2 ++
>>    arch/powerpc/kvm/timing.h              |  7 +++---
>>    include/linux/kvm_host.h               |  3 +++
>>    arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
>>    arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
>>    arch/powerpc/kvm/book3s_hv.c           | 30 +++++++++-----------------
>>    arch/powerpc/kvm/e500.c                |  1 +
>>    arch/powerpc/kvm/e500mc.c              |  1 +
>>    arch/powerpc/kvm/powerpc.c             | 15 ++++++++++---
>>    arch/powerpc/kvm/timing.c              | 20 ++++-------------
>>    virt/kvm/kvm_main.c                    |  3 +++
>>    12 files changed, 44 insertions(+), 49 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
>> index 2bcac6da0a4b..f29b66cc2163 100644
>> --- a/arch/powerpc/include/asm/kvm_host.h
>> +++ b/arch/powerpc/include/asm/kvm_host.h
>> @@ -296,7 +296,6 @@ struct kvm_arch {
>>    	bool dawr1_enabled;
>>    	pgd_t *pgtable;
>>    	u64 process_table;
>> -	struct dentry *debugfs_dir;
>>    	struct kvm_resize_hpt *resize_hpt; /* protected by kvm->lock */
>>    #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>>    #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
>> @@ -672,7 +671,6 @@ struct kvm_vcpu_arch {
>>    	u64 timing_min_duration[__NUMBER_OF_KVM_EXIT_TYPES];
>>    	u64 timing_max_duration[__NUMBER_OF_KVM_EXIT_TYPES];
>>    	u64 timing_last_exit;
>> -	struct dentry *debugfs_exit_timing;
>>    #endif
>>    
>>    #ifdef CONFIG_PPC_BOOK3S
>> @@ -828,8 +826,6 @@ struct kvm_vcpu_arch {
>>    	struct kvmhv_tb_accumulator rm_exit;	/* real-mode exit code */
>>    	struct kvmhv_tb_accumulator guest_time;	/* guest execution */
>>    	struct kvmhv_tb_accumulator cede_time;	/* time napping inside guest */
>> -
>> -	struct dentry *debugfs_dir;
>>    #endif /* CONFIG_KVM_BOOK3S_HV_EXIT_TIMING */
>>    };
>>    
>> @@ -868,4 +864,7 @@ static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
>>    static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
>>    static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
>>    
>> +#define __KVM_HAVE_ARCH_VCPU_DEBUGFS
>> +#define __KVM_HAVE_ARCH_KVM_DEBUGFS
>> +
>>    #endif /* __POWERPC_KVM_HOST_H__ */
>> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
>> index 6355a6980ccf..fd841e844b90 100644
>> --- a/arch/powerpc/include/asm/kvm_ppc.h
>> +++ b/arch/powerpc/include/asm/kvm_ppc.h
>> @@ -316,6 +316,8 @@ struct kvmppc_ops {
>>    	int (*svm_off)(struct kvm *kvm);
>>    	int (*enable_dawr1)(struct kvm *kvm);
>>    	bool (*hash_v3_possible)(void);
>> +	void (*create_vm_debugfs)(struct kvm *kvm);
>> +	void (*create_vcpu_debugfs)(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry);
>>    };
>>    
>>    extern struct kvmppc_ops *kvmppc_hv_ops;
>> diff --git a/arch/powerpc/kvm/timing.h b/arch/powerpc/kvm/timing.h
>> index feef7885ba82..36f7c201c6f1 100644
>> --- a/arch/powerpc/kvm/timing.h
>> +++ b/arch/powerpc/kvm/timing.h
>> @@ -14,8 +14,8 @@
>>    #ifdef CONFIG_KVM_EXIT_TIMING
>>    void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu);
>>    void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu);
>> -void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id);
>> -void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu);
>> +void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu,
>> +				struct dentry *debugfs_dentry);
>>    
>>    static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type)
>>    {
>> @@ -27,8 +27,7 @@ static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type)
>>    static inline void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu) {}
>>    static inline void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu) {}
>>    static inline void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu,
>> -						unsigned int id) {}
>> -static inline void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
>> +					      struct dentry *debugfs_dentry) {}
>>    static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type) {}
>>    #endif /* CONFIG_KVM_EXIT_TIMING */
>>    
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index ae7735b490b4..4f22b1201a0d 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -1021,6 +1021,9 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state);
>>    #ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS
>>    void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry);
>>    #endif
>> +#ifdef __KVM_HAVE_ARCH_KVM_DEBUGFS
>> +void kvm_arch_create_vm_debugfs(struct kvm *kvm);
>> +#endif
>>    
>>    int kvm_arch_hardware_enable(void);
>>    void kvm_arch_hardware_disable(void);
>> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
>> index c63e263312a4..33dae253a0ac 100644
>> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
>> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
>> @@ -2112,7 +2112,7 @@ static const struct file_operations debugfs_htab_fops = {
>>    
>>    void kvmppc_mmu_debugfs_init(struct kvm *kvm)
>>    {
>> -	debugfs_create_file("htab", 0400, kvm->arch.debugfs_dir, kvm,
>> +	debugfs_create_file("htab", 0400, kvm->debugfs_dentry, kvm,
>>    			    &debugfs_htab_fops);
>>    }
>>    
>> diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
>> index c5508744e14c..f4e083c20872 100644
>> --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
>> +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
>> @@ -1452,7 +1452,7 @@ static const struct file_operations debugfs_radix_fops = {
>>    
>>    void kvmhv_radix_debugfs_init(struct kvm *kvm)
>>    {
>> -	debugfs_create_file("radix", 0400, kvm->arch.debugfs_dir, kvm,
>> +	debugfs_create_file("radix", 0400, kvm->debugfs_dentry, kvm,
>>    			    &debugfs_radix_fops);
>>    }
>>    
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index c8f12b056968..046df9e0d462 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -2771,19 +2771,14 @@ static const struct file_operations debugfs_timings_ops = {
>>    };
>>    
>>    /* Create a debugfs directory for the vcpu */
>> -static void debugfs_vcpu_init(struct kvm_vcpu *vcpu, unsigned int id)
>> +static void kvmppc_arch_create_vcpu_debugfs_hv(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
>>    {
>> -	char buf[16];
>> -	struct kvm *kvm = vcpu->kvm;
>> -
>> -	snprintf(buf, sizeof(buf), "vcpu%u", id);
>> -	vcpu->arch.debugfs_dir = debugfs_create_dir(buf, kvm->arch.debugfs_dir);
>> -	debugfs_create_file("timings", 0444, vcpu->arch.debugfs_dir, vcpu,
>> +	debugfs_create_file("timings", 0444, debugfs_dentry, vcpu,
>>    			    &debugfs_timings_ops);
>>    }
>>    
>>    #else /* CONFIG_KVM_BOOK3S_HV_EXIT_TIMING */
>> -static void debugfs_vcpu_init(struct kvm_vcpu *vcpu, unsigned int id)
>> +static void kvmppc_arch_create_vcpu_debugfs_hv(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
>>    {
>>    }
>>    #endif /* CONFIG_KVM_BOOK3S_HV_EXIT_TIMING */
>> @@ -2907,8 +2902,6 @@ static int kvmppc_core_vcpu_create_hv(struct kvm_vcpu *vcpu)
>>    	vcpu->arch.cpu_type = KVM_CPU_3S_64;
>>    	kvmppc_sanity_check(vcpu);
>>    
>> -	debugfs_vcpu_init(vcpu, id);
>> -
>>    	return 0;
>>    }
>>    
>> @@ -5186,7 +5179,6 @@ void kvmppc_free_host_rm_ops(void)
>>    static int kvmppc_core_init_vm_hv(struct kvm *kvm)
>>    {
>>    	unsigned long lpcr, lpid;
>> -	char buf[32];
>>    	int ret;
>>    
>>    	mutex_init(&kvm->arch.uvmem_lock);
>> @@ -5319,16 +5311,14 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm)
>>    		kvm->arch.smt_mode = 1;
>>    	kvm->arch.emul_smt_mode = 1;
>>    
>> -	/*
>> -	 * Create a debugfs directory for the VM
>> -	 */
>> -	snprintf(buf, sizeof(buf), "vm%d", current->pid);
>> -	kvm->arch.debugfs_dir = debugfs_create_dir(buf, kvm_debugfs_dir);
>> +	return 0;
>> +}
>> +
>> +static void kvmppc_arch_create_vm_debugfs_hv(struct kvm *kvm)
>> +{
>>    	kvmppc_mmu_debugfs_init(kvm);
>>    	if (radix_enabled())
>>    		kvmhv_radix_debugfs_init(kvm);
>> -
>> -	return 0;
>>    }
>>    
>>    static void kvmppc_free_vcores(struct kvm *kvm)
>> @@ -5342,8 +5332,6 @@ static void kvmppc_free_vcores(struct kvm *kvm)
>>    
>>    static void kvmppc_core_destroy_vm_hv(struct kvm *kvm)
>>    {
>> -	debugfs_remove_recursive(kvm->arch.debugfs_dir);
>> -
>>    	if (!cpu_has_feature(CPU_FTR_ARCH_300))
>>    		kvm_hv_vm_deactivated();
>>    
>> @@ -5996,6 +5984,8 @@ static struct kvmppc_ops kvm_ops_hv = {
>>    	.svm_off = kvmhv_svm_off,
>>    	.enable_dawr1 = kvmhv_enable_dawr1,
>>    	.hash_v3_possible = kvmppc_hash_v3_possible,
>> +	.create_vcpu_debugfs = kvmppc_arch_create_vcpu_debugfs_hv,
>> +	.create_vm_debugfs = kvmppc_arch_create_vm_debugfs_hv,
>>    };
>>    
>>    static int kvm_init_subcore_bitmap(void)
>> diff --git a/arch/powerpc/kvm/e500.c b/arch/powerpc/kvm/e500.c
>> index 7e8b69015d20..d82e70c3e0a9 100644
>> --- a/arch/powerpc/kvm/e500.c
>> +++ b/arch/powerpc/kvm/e500.c
>> @@ -495,6 +495,7 @@ static struct kvmppc_ops kvm_ops_e500 = {
>>    	.emulate_op = kvmppc_core_emulate_op_e500,
>>    	.emulate_mtspr = kvmppc_core_emulate_mtspr_e500,
>>    	.emulate_mfspr = kvmppc_core_emulate_mfspr_e500,
>> +	.create_vcpu_debugfs = kvmppc_create_vcpu_debugfs,
>>    };
>>    
>>    static int __init kvmppc_e500_init(void)
>> diff --git a/arch/powerpc/kvm/e500mc.c b/arch/powerpc/kvm/e500mc.c
>> index 1c189b5aadcc..45eacd949f4b 100644
>> --- a/arch/powerpc/kvm/e500mc.c
>> +++ b/arch/powerpc/kvm/e500mc.c
>> @@ -381,6 +381,7 @@ static struct kvmppc_ops kvm_ops_e500mc = {
>>    	.emulate_op = kvmppc_core_emulate_op_e500,
>>    	.emulate_mtspr = kvmppc_core_emulate_mtspr_e500,
>>    	.emulate_mfspr = kvmppc_core_emulate_mfspr_e500,
>> +	.create_vcpu_debugfs = kvmppc_create_vcpu_debugfs,
>>    };
>>    
>>    static int __init kvmppc_e500mc_init(void)
>> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
>> index c248d6d8b9e3..c895521ac6e9 100644
>> --- a/arch/powerpc/kvm/powerpc.c
>> +++ b/arch/powerpc/kvm/powerpc.c
>> @@ -763,7 +763,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>>    		goto out_vcpu_uninit;
>>    
>>    	vcpu->arch.waitp = &vcpu->wait;
>> -	kvmppc_create_vcpu_debugfs(vcpu, vcpu->vcpu_id);
>>    	return 0;
>>    
>>    out_vcpu_uninit:
>> @@ -780,8 +779,6 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>>    	/* Make sure we're not using the vcpu anymore */
>>    	hrtimer_cancel(&vcpu->arch.dec_timer);
>>    
>> -	kvmppc_remove_vcpu_debugfs(vcpu);
>> -
>>    	switch (vcpu->arch.irq_type) {
>>    	case KVMPPC_IRQ_MPIC:
>>    		kvmppc_mpic_disconnect_vcpu(vcpu->arch.mpic, vcpu);
>> @@ -2505,3 +2502,15 @@ int kvm_arch_init(void *opaque)
>>    }
>>    
>>    EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_ppc_instr);
>> +
>> +void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
>> +{
>> +	if (vcpu->kvm->arch.kvm_ops->create_vcpu_debugfs)
>> +		vcpu->kvm->arch.kvm_ops->create_vcpu_debugfs(vcpu, debugfs_dentry);
>> +}
>> +
>> +void kvm_arch_create_vm_debugfs(struct kvm *kvm)
>> +{
>> +	if (kvm->arch.kvm_ops->create_vm_debugfs)
>> +		kvm->arch.kvm_ops->create_vm_debugfs(kvm);
>> +}
>> diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c
>> index ba56a5cbba97..e1c17afc714d 100644
>> --- a/arch/powerpc/kvm/timing.c
>> +++ b/arch/powerpc/kvm/timing.c
>> @@ -204,21 +204,9 @@ static const struct file_operations kvmppc_exit_timing_fops = {
>>    	.release = single_release,
>>    };
>>    
>> -void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id)
>> +void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu,
>> +				struct dentry *debugfs_dentry)
>>    {
>> -	static char dbg_fname[50];
>> -	struct dentry *debugfs_file;
>> -
>> -	snprintf(dbg_fname, sizeof(dbg_fname), "vm%u_vcpu%u_timing",
>> -		 current->pid, id);
>> -	debugfs_file = debugfs_create_file(dbg_fname, 0666, kvm_debugfs_dir,
>> -						vcpu, &kvmppc_exit_timing_fops);
>> -
>> -	vcpu->arch.debugfs_exit_timing = debugfs_file;
>> -}
>> -
>> -void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu)
>> -{
>> -	debugfs_remove(vcpu->arch.debugfs_exit_timing);
>> -	vcpu->arch.debugfs_exit_timing = NULL;
>> +	debugfs_create_file("timing", 0666, debugfs_dentry,
>> +			    vcpu, &kvmppc_exit_timing_fops);
>>    }
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index b50dbe269f4b..85b2550e18e7 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -954,6 +954,9 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
>>    				    kvm->debugfs_dentry, stat_data,
>>    				    &stat_fops_per_vm);
>>    	}
>> +#ifdef __KVM_HAVE_ARCH_KVM_DEBUGFS
>> +	kvm_arch_create_vm_debugfs(kvm);
>> +#endif
>>    	return 0;
>>    }
>>    
>>
> 

-- 
Alexey