From 7a0bac4da9c6a2e36d388412f3b4074b10429e8e Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Wed, 27 Jun 2012 14:50:47 +1000 Subject: Add a memory barrier to DMA functions The emulated devices can run simultaneously with the guest, so we need to be careful with ordering of load and stores done by them to the guest system memory, which need to be observed in the right order by the guest operating system. This adds a barrier call to the basic DMA read/write ops which is currently implemented as a smp_mb(), but could be later improved for more fine grained control of barriers. Additionally, a _relaxed() variant of the accessors is provided to easily convert devices who would be performance sensitive and negatively impacted by the change. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Anthony Liguori --- dma-helpers.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'dma-helpers.c') diff --git a/dma-helpers.c b/dma-helpers.c index 2e09ceb912..35cb500581 100644 --- a/dma-helpers.c +++ b/dma-helpers.c @@ -31,6 +31,8 @@ static void do_dma_memory_set(dma_addr_t addr, uint8_t c, dma_addr_t len) int dma_memory_set(DMAContext *dma, dma_addr_t addr, uint8_t c, dma_addr_t len) { + dma_barrier(dma, DMA_DIRECTION_FROM_DEVICE); + if (dma_has_iommu(dma)) { return iommu_dma_memory_set(dma, addr, c, len); } -- cgit v1.2.1