Re: [kvm-unit-tests PATCH v4 1/3] s390x: pv: implement routine to share/unshare memory

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

On 1/21/21 10:20 AM, Janosch Frank wrote:
> On 1/21/21 10:13 AM, 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>
>> Acked-by: Cornelia Huck <cohuck@redhat.com>
>> Acked-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  lib/s390x/asm/uv.h | 38 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 38 insertions(+)
>>
>> diff --git a/lib/s390x/asm/uv.h b/lib/s390x/asm/uv.h
>> index 4c2fc48..8400026 100644
>> --- a/lib/s390x/asm/uv.h
>> +++ b/lib/s390x/asm/uv.h
>> @@ -71,4 +71,42 @@ 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
>> +	};
>> +	int cc;
>> +
>> +	cc = uv_call(0, (u64)&uvcb);
>> +	if (!cc && uvcb.header.rc == 0x0001)
> 
> s/0x0001/UVC_RC_EXECUTED/
> 
> 
>> +		return 0;
>> +
>> +	report_info("cc %d response code: %04x", cc, uvcb.header.rc);
> 
> Will the print have the string UV in it or will I need to guess that a
> UV call failed?
> 
> I'm wondering if an assert would make more sense, if callers are
> interested in the uv rc they will need to write an own share function
> anyway.

Ok, I'll take that back. In the following patches you return NULL if the
share for an allocation fails and you check for NULL after every
allocation so this is fine by me.

> 
>> +	return -1;
>> +}
>> +
>> +/*
>> + * 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
>>
>