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powerpc/vphn: parsing code rewrite

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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>
This commit is contained in:
Greg Kurz 2015-02-23 16:14:37 +01:00 committed by Michael Ellerman
parent 4b6cfb2a8c
commit 3338a65bad
2 changed files with 40 additions and 20 deletions
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54
arch/powerpc/mm/vphn.c
View File

@ -2,44 +2,64 @@
#include "vphn.h"
/*
* Convert the associativity domain numbers returned from the hypervisor
* to the sequence they would appear in the ibm,associativity property.
* 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 recreate the original stream. */
/* 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++) {
if (be16_to_cpup(field) == VPHN_FIELD_UNUSED) {
/* All significant fields processed, and remaining
* fields contain the reserved value of all 1's.
* Just store them.
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[i] = *((__be32 *)field);
field += 2;
} else if (be16_to_cpup(field) & VPHN_FIELD_MSB) {
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[i] = cpu_to_be32(
be16_to_cpup(field) & VPHN_FIELD_MASK);
field++;
nr_assoc_doms++;
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
*/
unpacked[i] = *((__be32 *)field);
field += 2;
nr_assoc_doms++;
last = new;
is_32bit = true;
}
}

6
arch/powerpc/mm/vphn.h
View File

@ -6,10 +6,10 @@
#define VPHN_REGISTER_COUNT 6
/*
* 6 64-bit registers unpacked into 12 32-bit associativity values. To form
* the complete property we have to add the length in the first cell.
* 6 64-bit registers unpacked into up to 24 be32 associativity values. To
* form the complete property we have to add the length in the first cell.
*/
#define VPHN_ASSOC_BUFSIZE (VPHN_REGISTER_COUNT*sizeof(u64)/sizeof(u32) + 1)
#define VPHN_ASSOC_BUFSIZE (VPHN_REGISTER_COUNT*sizeof(u64)/sizeof(u16) + 1)
extern int vphn_unpack_associativity(const long *packed, __be32 *unpacked);