The RTAS call can be normal where retrieves the data form the
hypervisor once or sequence based RTAS call which has to
issue multiple times until the complete data is obtained. For
some of these sequence RTAS calls, the OS should not interleave
calls with different input until the sequence is completed.
The data is collected for each call and copy to the buffer
for the entire sequence during ioctl() handle and then expose
this buffer to the user space with read() handle.
One such sequence RTAS call is ibm,get-vpd and its support is
already included in the current code. To add the similar support
for other sequence based calls, move the common functions in to
separate file and update papr_rtas_sequence struct with the
following callbacks so that RTAS call specific code will be
defined and executed to complete the sequence.
struct papr_rtas_sequence {
int error;
void params;
void (*begin) (struct papr_rtas_sequence *);
void (*end) (struct papr_rtas_sequence *);
const char * (*work) (struct papr_rtas_sequence *, size_t *);
};
params: Input parameters used to pass for RTAS call.
Begin: RTAS call specific function to initialize data
including work area allocation.
End: RTAS call specific function to free up resources
(free work area) after the sequence is completed.
Work: The actual RTAS call specific function which collects
the data from the hypervisor.
Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Tested-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250416225743.596462-2-haren@linux.ibm.com
["fallen through the cracks" misc stuff]
A bunch of anon_inode_getfile() callers follow it with adjusting
->f_mode; we have a helper doing that now, so let's make use
of it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20250118014434.GT1977892@ZenIV
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Besides the obvious (and desired) difference between krealloc() and
kvrealloc(), there is some inconsistency in their function signatures and
behavior:
- krealloc() frees the memory when the requested size is zero, whereas
kvrealloc() simply returns a pointer to the existing allocation.
- krealloc() behaves like kmalloc() if a NULL pointer is passed, whereas
kvrealloc() does not accept a NULL pointer at all and, if passed,
would fault instead.
- krealloc() is self-contained, whereas kvrealloc() relies on the caller
to provide the size of the previous allocation.
Inconsistent behavior throughout allocation APIs is error prone, hence
make kvrealloc() behave like krealloc(), which seems superior in all
mentioned aspects.
Besides that, implementing kvrealloc() by making use of krealloc() and
vrealloc() provides oppertunities to grow (and shrink) allocations more
efficiently. For instance, vrealloc() can be optimized to allocate and
map additional pages to grow the allocation or unmap and free unused pages
to shrink the allocation.
[dakr@kernel.org: document concurrency restrictions]
Link: https://lkml.kernel.org/r/20240725125442.4957-1-dakr@kernel.org
[dakr@kernel.org: disable KASAN when switching to vmalloc]
Link: https://lkml.kernel.org/r/20240730185049.6244-2-dakr@kernel.org
[dakr@kernel.org: properly document __GFP_ZERO behavior]
Link: https://lkml.kernel.org/r/20240730185049.6244-5-dakr@kernel.org
Link: https://lkml.kernel.org/r/20240722163111.4766-3-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Chandan Babu R <chandan.babu@oracle.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
PowerVM LPARs may retrieve Vital Product Data (VPD) for system
components using the ibm,get-vpd RTAS function.
We can expose this to user space with a /dev/papr-vpd character
device, where the programming model is:
struct papr_location_code plc = { .str = "", }; /* obtain all VPD */
int devfd = open("/dev/papr-vpd", O_RDONLY);
int vpdfd = ioctl(devfd, PAPR_VPD_CREATE_HANDLE, &plc);
size_t size = lseek(vpdfd, 0, SEEK_END);
char *buf = malloc(size);
pread(devfd, buf, size, 0);
When a file descriptor is obtained from ioctl(PAPR_VPD_CREATE_HANDLE),
the file contains the result of a complete ibm,get-vpd sequence. The
file contents are immutable from the POV of user space. To get a new
view of the VPD, the client must create a new handle.
This design choice insulates user space from most of the complexities
that ibm,get-vpd brings:
* ibm,get-vpd must be called more than once to obtain complete
results.
* Only one ibm,get-vpd call sequence should be in progress at a time;
interleaved sequences will disrupt each other. Callers must have a
protocol for serializing their use of the function.
* A call sequence in progress may receive a "VPD changed, try again"
status, requiring the client to abandon the sequence and start
over.
The memory required for the VPD buffers seems acceptable, around 20KB
for all VPD on one of my systems. And the value of the
/rtas/ibm,vpd-size DT property (the estimated maximum size of VPD) is
consistently 300KB across various systems I've checked.
I've implemented support for this new ABI in the rtas_get_vpd()
function in librtas, which the vpdupdate command currently uses to
populate its VPD database. I've verified that an unmodified vpdupdate
binary generates an identical database when using a librtas.so that
prefers the new ABI.
Along with the papr-vpd.h header exposed to user space, this
introduces a common papr-miscdev.h uapi header to share a base ioctl
ID with similar drivers to come.
Tested-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231212-papr-sys_rtas-vs-lockdown-v6-9-e9eafd0c8c6c@linux.ibm.com
