kernel_optimize_test/arch/powerpc/mm/vphn.c
Greg Kurz 3338a65bad powerpc/vphn: parsing code rewrite
The current VPHN parsing logic has some flaws that this patch aims to fix:

1) when the value 0xffff is read, the value 0xffffffff gets added to the
   the output list and its element count isn't incremented. This is wrong.
   According to PAPR+ the domain identifiers are packed into a sequence
   terminated by the "reserved value of all ones". This means that 0xffff
   is a stream terminator.

2) the combination of byteswaps and casts make the code hardly readable.
   Let's parse the stream one 16-bit field at a time instead.

3) it is assumed that the hypercall returns 12 32-bit values packed into
   6 64-bit registers. According to PAPR+, the domain identifiers may be
   streamed as 16-bit values. Let's increase the number of expected numbers
   to 24.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2015-03-18 10:48:59 +11:00

71 lines
2.0 KiB
C

#include <asm/byteorder.h>
#include "vphn.h"
/*
* The associativity domain numbers are returned from the hypervisor as a
* stream of mixed 16-bit and 32-bit fields. The stream is terminated by the
* special value of "all ones" (aka. 0xffff) and its size may not exceed 48
* bytes.
*
* --- 16-bit fields -->
* _________________________
* | 0 | 1 | 2 | 3 | be_packed[0]
* ------+-----+-----+------
* _________________________
* | 4 | 5 | 6 | 7 | be_packed[1]
* -------------------------
* ...
* _________________________
* | 20 | 21 | 22 | 23 | be_packed[5]
* -------------------------
*
* Convert to the sequence they would appear in the ibm,associativity property.
*/
int vphn_unpack_associativity(const long *packed, __be32 *unpacked)
{
__be64 be_packed[VPHN_REGISTER_COUNT];
int i, nr_assoc_doms = 0;
const __be16 *field = (const __be16 *) be_packed;
u16 last = 0;
bool is_32bit = false;
#define VPHN_FIELD_UNUSED (0xffff)
#define VPHN_FIELD_MSB (0x8000)
#define VPHN_FIELD_MASK (~VPHN_FIELD_MSB)
/* Let's fix the values returned by plpar_hcall9() */
for (i = 0; i < VPHN_REGISTER_COUNT; i++)
be_packed[i] = cpu_to_be64(packed[i]);
for (i = 1; i < VPHN_ASSOC_BUFSIZE; i++) {
u16 new = be16_to_cpup(field++);
if (is_32bit) {
/* Let's concatenate the 16 bits of this field to the
* 15 lower bits of the previous field
*/
unpacked[++nr_assoc_doms] =
cpu_to_be32(last << 16 | new);
is_32bit = false;
} else if (new == VPHN_FIELD_UNUSED)
/* This is the list terminator */
break;
else if (new & VPHN_FIELD_MSB) {
/* Data is in the lower 15 bits of this field */
unpacked[++nr_assoc_doms] =
cpu_to_be32(new & VPHN_FIELD_MASK);
} else {
/* Data is in the lower 15 bits of this field
* concatenated with the next 16 bit field
*/
last = new;
is_32bit = true;
}
}
/* The first cell contains the length of the property */
unpacked[0] = cpu_to_be32(nr_assoc_doms);
return nr_assoc_doms;
}