Re: [PATCH 4/4] Use kmem cache for allocating vcpus, simplify FPU ops

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Rusty Russell wrote:
> If we use a kmem cache for allocating vcpus, we can get the 16-byte
> alignment required by fxsave & fxrstor instructions, and avoid
> manually aligning the buffer.
>
>   

Please separate the slabification from the fpu cleanups into separate 
patches.

> Signed-off-by: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
>
> diff -r 39421cbc0486 drivers/kvm/kvm.h
> --- a/drivers/kvm/kvm.h	Mon Jul 30 15:01:44 2007 +1000
> +++ b/drivers/kvm/kvm.h	Mon Jul 30 15:09:54 2007 +1000
> @@ -43,10 +43,6 @@
>  #define KVM_MIN_FREE_MMU_PAGES 5
>  #define KVM_REFILL_PAGES 25
>  #define KVM_MAX_CPUID_ENTRIES 40
> -
> -#define FX_IMAGE_SIZE 512
> -#define FX_IMAGE_ALIGN 16
> -#define FX_BUF_SIZE (2 * FX_IMAGE_SIZE + FX_IMAGE_ALIGN)
>  
>  #define DE_VECTOR 0
>  #define NM_VECTOR 7
> @@ -339,9 +335,8 @@ struct kvm_vcpu {
>  
>  	struct kvm_guest_debug guest_debug;
>  
> -	char fx_buf[FX_BUF_SIZE];
> -	char *host_fx_image;
> -	char *guest_fx_image;
> +	struct i387_fxsave_struct host_fx_image;
> +	struct i387_fxsave_struct guest_fx_image;
>   

So gcc is smart enough to propagate the alignment of i386_fxsave_struct 
to its container?  Nice.

>  
>  static int __init svm_init(void)
>  {
> -	return kvm_init_arch(&svm_arch_ops, THIS_MODULE);
> +	int err;
> +
> +	/* A kmem cache lets us meet the alignment requirements of fx_save. */
> +	svm_kmem_cache = KMEM_CACHE(vcpu_svm, 0);
>   

kvm slab caches are prefixed with kvm_; this makes it easy to 'grep kvm 
/proc/slabinfo' to see kvm leaks.  Please preserve that.

Also, the allocation and destruction can be in common code, reducing the 
amount of rarely-executed error paths.

-- 
error compiling committee.c: too many arguments to function


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