Re: [kvm-unit-tests PATCH v3 2/3] s390x: define UV compatible I/O allocation

[Pierre Morel <pmorel@linux.ibm.com>]

On 1/20/21 12:01 PM, Thomas Huth wrote:
> On 19/01/2021 20.52, Pierre Morel wrote:
>> To centralize the memory allocation for I/O we define
>> the alloc_io_page/free_io_page functions which share the I/O
>> memory with the host in case the guest runs with
>> protected virtualization.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   lib/s390x/malloc_io.c | 50 +++++++++++++++++++++++++++++++++++++++++++
>>   lib/s390x/malloc_io.h | 18 ++++++++++++++++
>>   s390x/Makefile        |  1 +
>>   3 files changed, 69 insertions(+)
>>   create mode 100644 lib/s390x/malloc_io.c
>>   create mode 100644 lib/s390x/malloc_io.h
>>
>> diff --git a/lib/s390x/malloc_io.c b/lib/s390x/malloc_io.c
>> new file mode 100644
>> index 0000000..2a946e0
>> --- /dev/null
>> +++ b/lib/s390x/malloc_io.c
>> @@ -0,0 +1,50 @@
>> +/*
>> + * I/O page allocation
>> + *
>> + * Copyright (c) 2021 IBM Corp
>> + *
>> + * Authors:
>> + *  Pierre Morel <pmorel@linux.ibm.com>
>> + *
>> + * This code is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License version 2.
> 
> Janosch recently started to introduce SPDX identifieres to the s390x 
> code, so I think it would be good to use them here, too.
> 
>> + * Using this interface provide host access to the allocated pages in
>> + * case the guest is a secure guest.
>> + * This is needed for I/O buffers.
>> + *
>> + */
>> +#include <libcflat.h>
>> +#include <asm/page.h>
>> +#include <asm/uv.h>
>> +#include <malloc_io.h>
>> +#include <alloc_page.h>
>> +#include <asm/facility.h>
>> +
>> +void *alloc_io_page(int size)
>> +{
>> +    void *p;
>> +
>> +    assert(size <= PAGE_SIZE);
> 
> Apart from the assert() statement, the size parameter seems to be 
> completely unused. It's also weird to have the function named 

right.

> alloc_something_page() and then have a parameter that takes bytes. Thus 
> I'd suggest to either drop the size parameter completely, or to rename 
> the function to alloc_io_mem and then to alloc multiple pages below in 
> case the size is bigger than PAGE_SIZE. Or maybe even to name the 
> function alloc_io_pages and then use "int num_pages" as a parameter, 
> allowing to allocate multiple pages at once?

OK, may bet using order as with the alloc_pages_flags would be fine.
Then I will need a new flag in the pages.

> 
>> +
>> +    p = alloc_pages_flags(1, AREA_DMA31);

humm 0 here (Claudio)

>> +    if (!p)
>> +        return NULL;
>> +    memset(p, 0, PAGE_SIZE);
>> +
>> +    if (!test_facility(158))
>> +        return p;
>> +
>> +    if (uv_set_shared((unsigned long)p) == 0)
>> +        return p;
>> +
>> +    free_pages(p);
>> +    return NULL;
>> +}
>> +
>> +void free_io_page(void *p)
>> +{
>> +    if (test_facility(158))
>> +        uv_remove_shared((unsigned long)p);
>> +    free_pages(p);
>> +}
>> diff --git a/lib/s390x/malloc_io.h b/lib/s390x/malloc_io.h
>> new file mode 100644
>> index 0000000..f780191
>> --- /dev/null
>> +++ b/lib/s390x/malloc_io.h
>> @@ -0,0 +1,18 @@
>> +/*
>> + * I/O allocations
>> + *
>> + * Copyright (c) 2021 IBM Corp
>> + *
>> + * Authors:
>> + *  Pierre Morel <pmorel@linux.ibm.com>
>> + *
>> + * This code is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License version 2.
>> + */
> Please also add SPDX license information here.

Will do.

Thanks for reviewing,
Pierre

> 
>   Thomas
> 

-- 
Pierre Morel
IBM Lab Boeblingen