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s390/pci: fix max size calculation in zpci_memcpy_toio() 

The zpci_get_max_write_size() helper is used to determine the maximum
size a PCI store or load can use at a given __iomem address.

For the PCI block store the following restrictions apply:

1. The dst + len must not cross a 4K boundary in the (pseudo-)MMIO space
2. len must not exceed ZPCI_MAX_WRITE_SIZE
3. len must be a multiple of 8 bytes
4. The src address must be double word (8 byte) aligned
5. The dst address must be double word (8 byte) aligned

Otherwise only a normal PCI store which takes its src value from
a register can be used. For these PCI store restriction 1 still applies.
Similarly 1 also applies to PCI loads.

It turns out zpci_max_write_size() instead implements stricter
conditions which prevents PCI block stores from being used where they
can and should be used. In particular instead of conditions 4 and 5 it
wrongly enforces both dst and src to be size aligned. This indirectly
covers condition 1 but also prevents many legal PCI block stores.

On top of the functional shortcomings the zpci_get_max_write_size() is
misnamed as it is used for both read and write size calculations. Rename
it to zpci_get_max_io_size() and implement the listed conditions
explicitly.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Fixes: cd24834130 ("s390/pci: base support")
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
[agordeev@linux.ibm.com replaced spaces with tabs]
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Niklas Schnelle 2023-11-28 16:22:49 +01:00 committed by Alexander Gordeev
parent 0130a0d3a6
commit 80df7d6af7
2 changed files with 24 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
arch/s390/include/asm/pci_io.h
View File

@ -11,6 +11,8 @@
/* I/O size constraints */
#define ZPCI_MAX_READ_SIZE 8
#define ZPCI_MAX_WRITE_SIZE 128
#define ZPCI_BOUNDARY_SIZE (1 << 12)
#define ZPCI_BOUNDARY_MASK (ZPCI_BOUNDARY_SIZE - 1)
/* I/O Map */
#define ZPCI_IOMAP_SHIFT 48
@ -125,16 +127,18 @@ out:
int zpci_write_block(volatile void __iomem *dst, const void *src,
unsigned long len);
static inline u8 zpci_get_max_write_size(u64 src, u64 dst, int len, int max)
static inline int zpci_get_max_io_size(u64 src, u64 dst, int len, int max)
{
int count = len > max ? max : len, size = 1;
int offset = dst & ZPCI_BOUNDARY_MASK;
int size;
while (!(src & 0x1) && !(dst & 0x1) && ((size << 1) <= count)) {
dst = dst >> 1;
src = src >> 1;
size = size << 1;
}
return size;
size = min3(len, ZPCI_BOUNDARY_SIZE - offset, max);
if (IS_ALIGNED(src, 8) && IS_ALIGNED(dst, 8) && IS_ALIGNED(size, 8))
return size;
if (size >= 8)
return 8;
return rounddown_pow_of_two(size);
}
static inline int zpci_memcpy_fromio(void *dst,
@ -144,9 +148,9 @@ static inline int zpci_memcpy_fromio(void *dst,
int size, rc = 0;
while (n > 0) {
size = zpci_get_max_write_size((u64 __force) src,
(u64) dst, n,
ZPCI_MAX_READ_SIZE);
size = zpci_get_max_io_size((u64 __force) src,
(u64) dst, n,
ZPCI_MAX_READ_SIZE);
rc = zpci_read_single(dst, src, size);
if (rc)
break;
@ -166,9 +170,9 @@ static inline int zpci_memcpy_toio(volatile void __iomem *dst,
return -EINVAL;
while (n > 0) {
size = zpci_get_max_write_size((u64 __force) dst,
(u64) src, n,
ZPCI_MAX_WRITE_SIZE);
size = zpci_get_max_io_size((u64 __force) dst,
(u64) src, n,
ZPCI_MAX_WRITE_SIZE);
if (size > 8) /* main path */
rc = zpci_write_block(dst, src, size);
else

12
arch/s390/pci/pci_mmio.c
View File

@ -97,9 +97,9 @@ static inline int __memcpy_toio_inuser(void __iomem *dst,
return -EINVAL;
while (n > 0) {
size = zpci_get_max_write_size((u64 __force) dst,
(u64 __force) src, n,
ZPCI_MAX_WRITE_SIZE);
size = zpci_get_max_io_size((u64 __force) dst,
(u64 __force) src, n,
ZPCI_MAX_WRITE_SIZE);
if (size > 8) /* main path */
rc = __pcistb_mio_inuser(dst, src, size, &status);
else
@ -242,9 +242,9 @@ static inline int __memcpy_fromio_inuser(void __user *dst,
u8 status;
while (n > 0) {
size = zpci_get_max_write_size((u64 __force) src,
(u64 __force) dst, n,
ZPCI_MAX_READ_SIZE);
size = zpci_get_max_io_size((u64 __force) src,
(u64 __force) dst, n,
ZPCI_MAX_READ_SIZE);
rc = __pcilg_mio_inuser(dst, src, size, &status);
if (rc)
break;