Re: [patch] fix kvm_arch_vcpu_ioctl_[gs]et_regs()

[Avi Kivity <avi@redhat.com>]

Jes Sorensen wrote:
> Hi,
>
> This patch makes these two macros do something sensible on ia64 and
> work the way qemu expects to use them. The old versions clearly couldn't
> have worked since the get_regs() call expected pointers in the kvm_regs
> struct which were never copied in.
>
> Fix kvm_arch_vcpu_ioctl_[gs]et_regs() to do something meaningful on
> ia64. Old versions could never have worked since they required
> pointers to be set in the ioctl payload which were never being set by
> the ioctl handler for get_regs.
>
> This version doesn't support copying the KVM kernel stack in/out of
> the kernel. This should be implemented in a seperate ioctl call if
> ever needed.
>
>  
>  struct kvm_regs {
> -	char *saved_guest;
> -	char *saved_stack;
>  	struct saved_vpd vpd;
>  	/*Arch-regs*/
>  	int mp_state;
> @@ -233,6 +231,8 @@
>  	unsigned long fp_psr;       /*used for lazy float register */
>  	unsigned long saved_gp;
>  	/*for phycial  emulation */
> +
> +	union context saved_guest;
>  };
>  
>   

This makes several tons of sense, but breaks backwards compatibility.  
If I understand correctly, get/set was never used so this shouldn't matter?

I suggest reserving some space at the end of kvm_regs in case further 
state needs to be added.

Please add a KVM_CAP_ entry to advertise the fixup.  This way userspace 
can determine that it's compiling or running on an old kernel and error 
out gracefully.

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