Re: [kvm PATCH v5 1/1] kvm: Make VM ioctl do valloc for some archs

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On 15.05.2018 13:37, Marc Orr wrote:
> The kvm struct has been bloating. For example, it's tens of kilo-bytes
> for x86, which turns out to be a large amount of memory to allocate
> contiguously via kzalloc. Thus, this patch does the following:
> 1. Uses architecture-specific routines to allocat the kvm struct via
>    kzalloc for x86 and also for arm when has_tbe() is true.
> 2. Introduces a baseline allocator for the kvm struct that uses valloc.
>    This allocator can be used by an architecture by defining the
>    __KVM_VALLOC_ARCH_VM macro before including include/linux/kvm_host.h.
> 3. Finally, continue to default to kalloc for all other situations, as
>    many architectures have taken a dependence on kalloc.
> 
> Signed-off-by: Marc Orr <marcorr@xxxxxxxxxx>
> Change-Id: Ide392e51991142d1325e06351231ac685e11d820
> ---
>  arch/arm/include/asm/kvm_host.h   |  4 ++++
>  arch/arm64/include/asm/kvm_host.h |  4 ++++
>  arch/x86/kvm/svm.c                |  4 ++--
>  arch/x86/kvm/vmx.c                |  4 ++--
>  include/linux/kvm_host.h          | 13 +++++++++++++
>  virt/kvm/arm/arm.c                | 15 +++++++++++++++
>  6 files changed, 40 insertions(+), 4 deletions(-)
> 

I thought we verified that s390x is also not a problem. Any reason not
to include it? (sorry if I am missing review comments from earlier
versions but if there is a reason, it should go into the cover letter)


> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index c7c28c885a19..f38fd60b4d4d 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -318,4 +318,8 @@ static inline bool kvm_arm_harden_branch_predictor(void)
>  static inline void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu) {}
>  static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
>  
> +#define __KVM_HAVE_ARCH_VM_ALLOC
> +struct kvm *kvm_arch_alloc_vm(void);
> +void kvm_arch_free_vm(struct kvm *kvm);
> +
>  #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 469de8acd06f..358b1b4dcd92 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -455,4 +455,8 @@ static inline bool kvm_arm_harden_branch_predictor(void)
>  void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
>  void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
>  
> +#define __KVM_HAVE_ARCH_VM_ALLOC
> +struct kvm *kvm_arch_alloc_vm(void);
> +void kvm_arch_free_vm(struct kvm *kvm);
> +
>  #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 1fc05e428aba..45b903ed3e5d 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1849,13 +1849,13 @@ static void __unregister_enc_region_locked(struct kvm *kvm,
>  
>  static struct kvm *svm_vm_alloc(void)
>  {
> -	struct kvm_svm *kvm_svm = kzalloc(sizeof(struct kvm_svm), GFP_KERNEL);
> +	struct kvm_svm *kvm_svm = vzalloc(sizeof(struct kvm_svm));
>  	return &kvm_svm->kvm;
>  }
>  
>  static void svm_vm_free(struct kvm *kvm)
>  {
> -	kfree(to_kvm_svm(kvm));
> +	vfree(to_kvm_svm(kvm));
>  }
>  
>  static void sev_vm_destroy(struct kvm *kvm)
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 3f1696570b41..ee85ba887db6 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -9936,13 +9936,13 @@ STACK_FRAME_NON_STANDARD(vmx_vcpu_run);
>  
>  static struct kvm *vmx_vm_alloc(void)
>  {
> -	struct kvm_vmx *kvm_vmx = kzalloc(sizeof(struct kvm_vmx), GFP_KERNEL);
> +	struct kvm_vmx *kvm_vmx = vzalloc(sizeof(struct kvm_vmx));
>  	return &kvm_vmx->kvm;
>  }
>  
>  static void vmx_vm_free(struct kvm *kvm)
>  {
> -	kfree(to_kvm_vmx(kvm));
> +	vfree(to_kvm_vmx(kvm));
>  }
>  
>  static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 6d6e79c59e68..e3134283321a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -19,6 +19,7 @@
>  #include <linux/preempt.h>
>  #include <linux/msi.h>
>  #include <linux/slab.h>
> +#include <linux/vmalloc.h>
>  #include <linux/rcupdate.h>
>  #include <linux/ratelimit.h>
>  #include <linux/err.h>
> @@ -808,6 +809,17 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
>  
>  #ifndef __KVM_HAVE_ARCH_VM_ALLOC
> +#ifdef __KVM_VALLOC_ARCH_VM
> +static inline struct kvm *kvm_arch_alloc_vm(void)
> +{
> +	return vzalloc(sizeof(struct kvm));
> +}
> +
> +static inline void kvm_arch_free_vm(struct kvm *kvm)
> +{
> +	vfree(kvm);
> +}
> +#else
>  static inline struct kvm *kvm_arch_alloc_vm(void)
>  {
>  	return kzalloc(sizeof(struct kvm), GFP_KERNEL);
> @@ -818,6 +830,7 @@ static inline void kvm_arch_free_vm(struct kvm *kvm)
>  	kfree(kvm);
>  }
>  #endif
> +#endif
>  
>  #ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
>  void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index a4c1b76240df..ee96f18f852a 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -249,6 +249,21 @@ long kvm_arch_dev_ioctl(struct file *filp,
>  	return -EINVAL;
>  }
>  
> +struct kvm *kvm_arch_alloc_vm(void)
> +{
> +	if (!has_vhe())
> +		return kzalloc(sizeof(struct kvm), GFP_KERNEL);
> +
> +	return vzalloc(sizeof(struct kvm));
> +}
> +
> +void kvm_arch_free_vm(struct kvm *kvm)
> +{
> +	if (!has_vhe())
> +		kfree(kvm);
> +	else
> +		vfree(kvm);
> +}
>  
>  struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
>  {
> 


-- 

Thanks,

David / dhildenb



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