Re: [PATCH 1/4] [HYPERCALL] Add hypercalls functions

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

Dor Laor wrote:
> The hypercalls can be called with various parameters number.
> Both x86_64 and i386 are supported.
>
> Signed-off-by: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> ---
>  include/asm-i386/hypercall.h   |  142
> ++++++++++++++++++++++++++++++++++++++++
>  include/asm-x86_64/hypercall.h |  105 +++++++++++++++++++++++++++++
>  2 files changed, 247 insertions(+), 0 deletions(-)
>  create mode 100644 include/asm-i386/hypercall.h
>  create mode 100644 include/asm-x86_64/hypercall.h
>
> diff --git a/include/asm-i386/hypercall.h b/include/asm-i386/hypercall.h
> new file mode 100644
> index 0000000..40fd31e
> --- /dev/null
> +++ b/include/asm-i386/hypercall.h
> @@ -0,0 +1,142 @@
> +
> +#define CONFIG_PARAVIRT 1
>   

??

> +#ifdef CONFIG_PARAVIRT
> +
> +/*
> + * Hypercalls, according to the calling convention
> + * documented in include/linux/kvm_para.h
> + *
> + * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> + * Copyright (C) 2007, Qumranet, Inc., Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> See
> + * the COPYING file in the top-level directory.
> + */
> +
> +static inline int __hypercall0(unsigned int nr)
>   

These should be called __kvm_hypercallX() (and the file renamed as
well).  Linux guests support multiple hypevisors with different calling
conventions.

> +{
> +	int ret;
> +	asm (" call hypercall_addr\n"
>   

I think "asm volatile" can allow you to avoid the volatile...

> +
> +#define hypercall(nr_params, args...)			\
> +({							\
> +	/* __ret is volatile to make sure call to this	\
> +	 * function isn't optimized away by gcc. Just	\
> +	 * having the __hypercallN() functions mention	\
> +	 * memory is clobbered isn't enough		\
> +	 */						\
> +	volatile int __ret;				\
> +							\
> +	__ret = __hypercall##nr_params(args);		\
> +							\
> +	__ret;						\
> +})
>   

...here.  In fact the statement expression can go away.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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