Re: [PATCH v2 6/8] s390/mm: Thread pgprot_t through vmem_add_mapping()

[Logan Gunthorpe]

On 2020-01-08 5:43 a.m., David Hildenbrand wrote:
> On 07.01.20 21:59, Logan Gunthorpe wrote:
>> In prepartion to support a pgprot_t argument for arch_add_memory().
>>
>> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
>> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
>> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
>> ---
>>  arch/s390/include/asm/pgtable.h |  3 ++-
>>  arch/s390/mm/extmem.c           |  3 ++-
>>  arch/s390/mm/init.c             |  2 +-
>>  arch/s390/mm/vmem.c             | 10 +++++-----
>>  4 files changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
>> index 7b03037a8475..e667a1a96879 100644
>> --- a/arch/s390/include/asm/pgtable.h
>> +++ b/arch/s390/include/asm/pgtable.h
>> @@ -1640,7 +1640,8 @@ static inline swp_entry_t __swp_entry(unsigned long type, unsigned long offset)
>>  
>>  #define kern_addr_valid(addr)   (1)
>>  
>> -extern int vmem_add_mapping(unsigned long start, unsigned long size);
>> +extern int vmem_add_mapping(unsigned long start, unsigned long size,
>> +			    pgprot_t prot);
>>  extern int vmem_remove_mapping(unsigned long start, unsigned long size);
>>  extern int s390_enable_sie(void);
>>  extern int s390_enable_skey(void);
>> diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c
>> index fd0dae9d10f4..6cf7029a7b35 100644
>> --- a/arch/s390/mm/extmem.c
>> +++ b/arch/s390/mm/extmem.c
>> @@ -313,7 +313,8 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
>>  		goto out_free;
>>  	}
>>  
>> -	rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
>> +	rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1,
>> +			      PAGE_KERNEL);
>>  
>>  	if (rc)
>>  		goto out_free;
>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>> index a0c88c1c9ad0..ef19522ddad2 100644
>> --- a/arch/s390/mm/init.c
>> +++ b/arch/s390/mm/init.c
>> @@ -277,7 +277,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
>>  	if (WARN_ON_ONCE(modifiers->altmap))
>>  		return -EINVAL;
>>  
>> -	rc = vmem_add_mapping(start, size);
>> +	rc = vmem_add_mapping(start, size, PAGE_KERNEL);
>>  	if (rc)
>>  		return rc;
>>  
>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
>> index b403fa14847d..8a5e95f184a2 100644
>> --- a/arch/s390/mm/vmem.c
>> +++ b/arch/s390/mm/vmem.c
>> @@ -66,7 +66,7 @@ pte_t __ref *vmem_pte_alloc(void)
>>  /*
>>   * Add a physical memory range to the 1:1 mapping.
>>   */
>> -static int vmem_add_mem(unsigned long start, unsigned long size)
>> +static int vmem_add_mem(unsigned long start, unsigned long size, pgprot_t prot)
>>  {
>>  	unsigned long pgt_prot, sgt_prot, r3_prot;
>>  	unsigned long pages4k, pages1m, pages2g;
>> @@ -79,7 +79,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
>>  	pte_t *pt_dir;
>>  	int ret = -ENOMEM;
>>  
>> -	pgt_prot = pgprot_val(PAGE_KERNEL);
>> +	pgt_prot = pgprot_val(prot);
>>  	sgt_prot = pgprot_val(SEGMENT_KERNEL);
>>  	r3_prot = pgprot_val(REGION3_KERNEL);
> 
> So, if we map as huge/gigantic pages, the protection would be discarded?
> That looks wrong.
> 
> s390x does not support ZONE_DEVICE yet. Maybe simply bail out for s390x
> as you do for sh to make your life easier?

Yeah, ok, makes sense to me; I'll change it for v3.

Logan