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port-i386/38935: Add appropriate x86_lfence or x86_mfence calls to

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bus_dmamap_sync(), depending on the BUS_DMASYNC flag. This makes sure
that the kernel reads data from main memory in the intended order.
This commit is contained in:
bouyer 2008-06-28 17:23:01 +00:00
parent b4c1afd422
commit caba2baea2
1 changed files with 18 additions and 3 deletions
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21
sys/arch/x86/x86/bus_dma.c
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@ -1,4 +1,4 @@
/* $NetBSD: bus_dma.c,v 1.44 2008/06/13 09:53:46 bjs Exp $ */
/* $NetBSD: bus_dma.c,v 1.45 2008/06/28 17:23:01 bouyer Exp $ */
/*-
* Copyright (c) 1996, 1997, 1998, 2007 The NetBSD Foundation, Inc.
@ -31,7 +31,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.44 2008/06/13 09:53:46 bjs Exp $");
__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.45 2008/06/28 17:23:01 bouyer Exp $");
/*
* The following is included because _bus_dma_uiomove is derived from
@ -722,7 +722,7 @@ _bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t offset,
*/
if (len == 0 || cookie == NULL ||
(cookie->id_flags & X86_DMA_IS_BOUNCING) == 0)
return;
goto end;
switch (cookie->id_buftype) {
case X86_DMA_BUFTYPE_LINEAR:
@ -844,6 +844,21 @@ _bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t offset,
printf("unknown buffer type %d\n", cookie->id_buftype);
panic("_bus_dmamap_sync");
}
end:
if (ops & (BUS_DMASYNC_PREWRITE|BUS_DMASYNC_POSTWRITE)) {
/*
* from the memory POV a load can be reordered before a store
* (a load can fetch data from the write buffers, before
* data hits the cache or memory), a mfence avoids it.
*/
x86_mfence();
} else if (ops & (BUS_DMASYNC_PREREAD|BUS_DMASYNC_POSTREAD)) {
/*
* all past reads should have completed at before this point,
* and futur reads should not have started yet.
*/
x86_lfence();
}
}
/*