[PATCH v2 12/16] vfio/ccw: calculate number of IDAWs regardless of format

Eric Farman
2022-12-20T17:11:47Z

The idal_nr_words() routine works well for 4K IDAWs, but lost its
ability to handle the old 2K formats with the removal of 31-bit
builds in commit 5a79859ae0f3 ("s390: remove 31 bit support").

Since there's nothing preventing a guest from generating this IDAW
format, let's re-introduce the math for them and use both when
calculating the number of IDAWs based on the bits specified in
the ORB.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
arch/s390/include/asm/idals.h | 12 ++++++++++++
drivers/s390/cio/vfio_ccw_cp.c | 16 ++++++++++++++++
2 files changed, 28 insertions(+)

diff --git a/arch/s390/include/asm/idals.h b/arch/s390/include/asm/idals.h
index 40eae2c08d61..59fcc3c72edf 100644
--- a/arch/s390/include/asm/idals.h
+++ b/arch/s390/include/asm/idals.h
@@ -23,6 +23,9 @@
#define IDA_SIZE_LOG 12 /* 11 for 2k , 12 for 4k */
#define IDA_BLOCK_SIZE (1L<<IDA_SIZE_LOG)

+#define IDA_2K_SIZE_LOG 11
+#define IDA_2K_BLOCK_SIZE (1L << IDA_2K_SIZE_LOG)
+
/*
* Test if an address/length pair needs an idal list.
*/
@@ -42,6 +45,15 @@ static inline unsigned int idal_nr_words(void *vaddr, unsigned int length)
(IDA_BLOCK_SIZE-1)) >> IDA_SIZE_LOG;
}

+/*
+ * Return the number of 2K IDA words needed for an address/length pair.
+ */
+static inline unsigned int idal_2k_nr_words(void *vaddr, unsigned int length)
+{
+ return ((__pa(vaddr) & (IDA_2K_BLOCK_SIZE - 1)) + length +
+ (IDA_2K_BLOCK_SIZE - 1)) >> IDA_2K_SIZE_LOG;
+}
+
/*
* Create the list of idal words for an address/length pair.
*/
diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 29d1e418b2e2..62a013a631d8 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -502,6 +502,13 @@ static int ccwchain_fetch_tic(struct ccw1 *ccw,
*
* @ccw: The Channel Command Word being translated
* @cp: Channel Program being processed
+ *
+ * The ORB is examined, since it specifies what IDAWs could actually be
+ * used by any CCW in the channel program, regardless of whether or not
+ * the CCW actually does. An ORB that does not specify Format-2-IDAW
+ * Control could still contain a CCW with an IDAL, which would be
+ * Format-1 and thus only move 2K with each IDAW. Thus all CCWs within
+ * the channel program must follow the same size requirements.
*/
static int ccw_count_idaws(struct ccw1 *ccw,
struct channel_program *cp)
@@ -530,6 +537,15 @@ static int ccw_count_idaws(struct ccw1 *ccw,
iova = ccw->cda;
}

+ /* Format-1 IDAWs operate on 2K each */
+ if (!cp->orb.cmd.c64)
+ return idal_2k_nr_words((void *)iova, bytes);
+
+ /* Using the 2K variant of Format-2 IDAWs? */
+ if (cp->orb.cmd.i2k)
+ return idal_2k_nr_words((void *)iova, bytes);
+
+ /* The 'usual' case is 4K Format-2 IDAWs */
return idal_nr_words((void *)iova, bytes);
}

--
2.34.1