Re: [PATCH/RFC] Per-architecture hypercall definitions

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Christian Borntraeger wrote:
> ---
>  include/asm-s390/kvm_para.h |  128 ++++++++++++++++++++++++++++++++++++++++++++
>  include/asm-x86/kvm_para.h  |  110 +++++++++++++++++++++++++++++++++++++
>  include/linux/kvm_para.h    |  112 ++++----------------------------------
>  3 files changed, 251 insertions(+), 99 deletions(-)
>
> Index: kvm/include/asm-x86/kvm_para.h
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ kvm/include/asm-x86/kvm_para.h	2007-10-11 14:05:25.000000000 +0200
> @@ -0,0 +1,108 @@
> +#ifndef __X86_KVM_PARA_H
> +#define __X86_KVM_PARA_H
> +
> +/* This CPUID returns the signature 'KVMKVMKVM' in ebx, ecx, and edx.  It
> + * should be used to determine that a VM is running under KVM.
> + */
> +#define KVM_CPUID_SIGNATURE	0x40000000
> +
> +/* This CPUID returns a feature bitmap in eax.  Before enabling a particular
> + * paravirtualization, the appropriate feature bit should be checked.
> + */
> +#define KVM_CPUID_FEATURES	0x40000001
> +
> +/* Return values for hypercalls */
> +#define KVM_ENOSYS		1000
>   

errno's can probably be in common code, right?

>  
> +#define kvm_hypercall(nr_params, args...)		\
> +({							\
> +	long __ret;					\
> +							\
> +	__ret = kvm_hypercall##nr_params(args);		\
> +							\
> +	__ret;						\
> +})
>   

Why store results to a variable?  It would also probably be better to 
use the C99 variadic macro format which would be:

#define kvm_hypercall(nr_params, ...) kvm_hypercall##nr_params(__VA_ARGS__)

I originally had one of these in my paravirt_ops implementation but 
quickly found that the code it produced was pretty ugly.  I think:

kvm_hypercall0(KVM_HYPERCALL_FOO);

Is a lot more understandable than:

kvm_hypercall(0, KVM_HYPERCALL_FOO);

It's much harder to guess with the later what the significance of the 
first parameter is.

Regards,

Anthony Liguori

> +#endif
>  #endif
> Index: kvm/include/asm-s390/kvm_para.h
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ kvm/include/asm-s390/kvm_para.h	2007-10-11 14:09:12.000000000 +0200
> @@ -0,0 +1,146 @@
> +#ifndef __S390_KVM_PARA_H
> +#define __S390_KVM_PARA_H
> +
> +/*
> + * This is subject to change:
> + *
> + * Hypercalls for KVM on s390. The calling convention is similar to the
> + * s390 ABI, so we use R2-R6 for parameters 1-5. In addition we use R1
> + * as hypercall number and R7 as parameter 6. The return value is
> + * written to R2. We use the diagnose instruction as hypercall. To avoid
> + * conflicts with existing diagnoses for LPAR and z/VM, we do not use
> + * the instruction encoded number, but specify the number in R1 and
> + * use 0xBB as KVM diagnose number.
> + *
> + * Copyright 2007, IBM Corp.
> + * Author(s) Christian Borntraeger <borntraeger-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + */
> +
> +static inline long kvm_hypercall0(unsigned long nr)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr): "memory", "cc");
> +	return __rc;
> +}
> +
> +static inline long kvm_hypercall1(unsigned long nr, unsigned long p1)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1) : "memory", "cc");
> +	return __rc;
> +}
> +
> +static inline long kvm_hypercall2(unsigned long nr, unsigned long p1,
> +			       unsigned long p2)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register unsigned long __p2 asm("3") = p2;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2)
> +		      : "memory", "cc");
> +	return __rc;
> +}
> +
> +static inline long kvm_hypercall3(unsigned long nr, unsigned long p1,
> +			       unsigned long p2, unsigned long p3)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register unsigned long __p2 asm("3") = p2;
> +	register unsigned long __p3 asm("4") = p3;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
> +			"d" (__p3) : "memory", "cc");
> +	return __rc;
> +}
> +
> +
> +static inline long kvm_hypercall4(unsigned long nr, unsigned long p1,
> +			       unsigned long p2, unsigned long p3,
> +			       unsigned long p4)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register unsigned long __p2 asm("3") = p2;
> +	register unsigned long __p3 asm("4") = p3;
> +	register unsigned long __p4 asm("5") = p4;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
> +			"d" (__p3), "d" (__p4) : "memory", "cc");
> +	return __rc;
> +}
> +
> +static inline long kvm_hypercall5(unsigned long nr, unsigned long p1,
> +			       unsigned long p2, unsigned long p3,
> +			       unsigned long p4, unsigned long p5)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register unsigned long __p2 asm("3") = p2;
> +	register unsigned long __p3 asm("4") = p3;
> +	register unsigned long __p4 asm("5") = p4;
> +	register unsigned long __p5 asm("6") = p5;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
> +			"d" (__p3), "d" (__p4), "d" (__p5)  : "memory", "cc");
> +	return __rc;
> +}
> +
> +static inline long kvm_hypercall6(unsigned long nr, unsigned long p1,
> +			       unsigned long p2, unsigned long p3,
> +			       unsigned long p4, unsigned long p5,
> +			       unsigned long p6)
> +{
> +	register unsigned long __nr asm("1") = nr;
> +	register unsigned long __p1 asm("2") = p1;
> +	register unsigned long __p2 asm("3") = p2;
> +	register unsigned long __p3 asm("4") = p3;
> +	register unsigned long __p4 asm("5") = p4;
> +	register unsigned long __p5 asm("6") = p5;
> +	register unsigned long __p6 asm("7") = p6;
> +	register long __rc asm("2");
> +
> +	asm volatile ("diag 2,4,0xBB\n"
> +		      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
> +			"d" (__p3), "d" (__p4), "d" (__p5), "d" (__p6)
> +		      : "memory", "cc");
> +	return __rc;
> +}
> +
> +/*
> + * FIXME: make a real check as soon as we define how to check
> + */
> +static inline int kvm_para_available(void)
> +{
> +	return 1;
> +}
> +
> +/*
> + * FIXME: return available features
> + */
> +static inline unsigned int kvm_arch_para_features(void)
> +{
> +	return 0;
> +}
> +
> +
> +
> +#endif /* __S390_KVM_PARA_H */
>
>
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