Re: [PATCH] vmx: enable io bitmaps to avoid IO port 0x80 VMEXITs

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

He, Qing wrote:
> This patch enables IO bitmaps control on vmx and unmask the 0x80 port to
> avoid VMEXITs caused by accessing port 0x80. 0x80 is used as delays (see
> include/asm/io.h), and handling VMEXITs on its access is unnecessary but
> slows things down. This patch improves kernel build test at around
> 3%~5%.
>   

It's quite surprising to see such a large speedup!


> +
>  #ifdef CONFIG_X86_64
>  #define HOST_IS_64 1
>  #else
> @@ -1127,8 +1129,8 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
>  	vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
>  
>  	/* I/O */
> -	vmcs_write64(IO_BITMAP_A, 0);
> -	vmcs_write64(IO_BITMAP_B, 0);
> +	vmcs_write64(IO_BITMAP_A, (unsigned long) __pa(vmx_io_bitmap));
> +	vmcs_write64(IO_BITMAP_B, (unsigned long) __pa(vmx_io_bitmap +
> PAGE_SIZE));
>   

Unnecessary casts.

> +	r = kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
> +	if (r) {
> +		goto out1;
> +	}
>   

No braces around single statements in kernel code, please.

> +
> +	return 0;
> +
> +out1:
> +	free_pages((unsigned long) vmx_io_bitmap, 1);
> +out:
> +	return r;
>  }
>  
>  static void __exit vmx_exit(void)
>  {
> +	if (vmx_io_bitmap)
> +		free_pages((unsigned long) vmx_io_bitmap, 1);
>   

The if is unnecessary, since we can't get here with a NULL vmx_io_bitmap 
(also free_pages() checks for NULL).

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


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