Re: [PATCH v1 2/4] s390x: pv: implement routine to share/unshare memory

[Janosch Frank <frankja@linux.ibm.com>]

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On 9/25/20 6:02 PM, Pierre Morel wrote:
> When communicating with the host we need to share part of
> the memory.
> 
> Let's implement the ultravisor calls for this.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Suggested-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  lib/s390x/asm/uv.h | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/lib/s390x/asm/uv.h b/lib/s390x/asm/uv.h
> index 4c2fc48..19019e4 100644
> --- a/lib/s390x/asm/uv.h
> +++ b/lib/s390x/asm/uv.h
> @@ -71,4 +71,37 @@ static inline int uv_call(unsigned long r1, unsigned long r2)
>  	return cc;
>  }
>  
> +static inline int share(unsigned long addr, u16 cmd)
> +{
> +	struct uv_cb_share uvcb = {
> +		.header.cmd = cmd,
> +		.header.len = sizeof(uvcb),
> +		.paddr = addr
> +	};
> +
> +	uv_call(0, (u64)&uvcb);
> +	return uvcb.header.rc;

That's not a great idea, rc is > 1 for error codes...
In the kernel we check for the cc instead since uv_call() has only 0/1
as possible cc return values.

> +}
> +
> +/*
> + * Guest 2 request to the Ultravisor to make a page shared with the
> + * hypervisor for IO.
> + *
> + * @addr: Real or absolute address of the page to be shared
> + */
> +static inline int uv_set_shared(unsigned long addr)
> +{
> +	return share(addr, UVC_CMD_SET_SHARED_ACCESS);
> +}
> +
> +/*
> + * Guest 2 request to the Ultravisor to make a page unshared.
> + *
> + * @addr: Real or absolute address of the page to be unshared
> + */
> +static inline int uv_remove_shared(unsigned long addr)
> +{
> +	return share(addr, UVC_CMD_REMOVE_SHARED_ACCESS);
> +}
> +
>  #endif
> 



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