git: 3a1802fef4b5 - main - busdma: Add an internal BUS_DMA_FORCE_MAP flag to x86 bounce_busdma

[Mark Johnston]

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=3a1802fef4b535d22b7f0d3fa6e0bc2de5003922

commit 3a1802fef4b535d22b7f0d3fa6e0bc2de5003922
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-08-10 21:11:43 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-08-11 01:27:54 +0000

    busdma: Add an internal BUS_DMA_FORCE_MAP flag to x86 bounce_busdma
    
    Use this flag to indicate that busdma should allocate a map structure
    even no bouncing is required to satisfy the tag's constraints.  This
    will be used for KMSAN.
    
    Also fix a memory leak that can occur if the kernel fails to allocate
    bounce pages in bounce_bus_dmamap_create().
    
    Reviewed by:    kib
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D31338
---
 sys/x86/x86/busdma_bounce.c | 43 +++++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/sys/x86/x86/busdma_bounce.c b/sys/x86/x86/busdma_bounce.c
index 75fdf4143b9b..d89d4d5a17ff 100644
--- a/sys/x86/x86/busdma_bounce.c
+++ b/sys/x86/x86/busdma_bounce.c
@@ -66,6 +66,7 @@ enum {
 	BUS_DMA_COULD_BOUNCE	= 0x01,
 	BUS_DMA_MIN_ALLOC_COMP	= 0x02,
 	BUS_DMA_KMEM_ALLOC	= 0x04,
+	BUS_DMA_FORCE_MAP	= 0x08,
 };
 
 struct bounce_zone;
@@ -301,7 +302,7 @@ bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 	error = 0;
 
 	if (dmat->segments == NULL) {
-		dmat->segments = (bus_dma_segment_t *)malloc_domainset(
+		dmat->segments = malloc_domainset(
 		    sizeof(bus_dma_segment_t) * dmat->common.nsegments,
 		    M_DEVBUF, DOMAINSET_PREF(dmat->common.domain), M_NOWAIT);
 		if (dmat->segments == NULL) {
@@ -311,6 +312,19 @@ bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 		}
 	}
 
+	if (dmat->bounce_flags & (BUS_DMA_COULD_BOUNCE | BUS_DMA_FORCE_MAP)) {
+		*mapp = malloc_domainset(sizeof(**mapp), M_DEVBUF,
+		    DOMAINSET_PREF(dmat->common.domain), M_NOWAIT | M_ZERO);
+		if (*mapp == NULL) {
+			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
+			    __func__, dmat, ENOMEM);
+			return (ENOMEM);
+		}
+		STAILQ_INIT(&(*mapp)->bpages);
+	} else {
+		*mapp = NULL;
+	}
+
 	/*
 	 * Bouncing might be required if the driver asks for an active
 	 * exclusion region, a data alignment that is stricter than 1, and/or
@@ -318,23 +332,11 @@ bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 	 */
 	if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0) {
 		/* Must bounce */
-		if (dmat->bounce_zone == NULL) {
-			if ((error = alloc_bounce_zone(dmat)) != 0)
-				return (error);
-		}
+		if (dmat->bounce_zone == NULL &&
+		    (error = alloc_bounce_zone(dmat)) != 0)
+			goto out;
 		bz = dmat->bounce_zone;
 
-		*mapp = (bus_dmamap_t)malloc_domainset(sizeof(**mapp), M_DEVBUF,
-		    DOMAINSET_PREF(dmat->common.domain), M_NOWAIT | M_ZERO);
-		if (*mapp == NULL) {
-			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
-			    __func__, dmat, ENOMEM);
-			return (ENOMEM);
-		}
-
-		/* Initialize the new map */
-		STAILQ_INIT(&((*mapp)->bpages));
-
 		/*
 		 * Attempt to add pages to our pool on a per-instance
 		 * basis up to a sane limit.
@@ -361,11 +363,16 @@ bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 				error = 0;
 		}
 		bz->map_count++;
+	}
+
+out:
+	if (error == 0) {
+		dmat->map_count++;
 	} else {
+		free(*mapp, M_DEVBUF);
 		*mapp = NULL;
 	}
-	if (error == 0)
-		dmat->map_count++;
+
 	CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
 	    __func__, dmat, dmat->common.flags, error);
 	return (error);