Commit 3338a65b authored by Greg Kurz's avatar Greg Kurz Committed by Michael Ellerman
Browse files

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: default avatarGreg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 4b6cfb2a

arch/powerpc/mm/vphn.c

+37 −17
Original line number Diff line number Diff line
@@ -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;

		}

	}

arch/powerpc/mm/vphn.h

+3 −3
Original line number Diff line number Diff line
@@ -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);

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