motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-12-11 16:00:50 -07:00
Code Issues Projects Releases Packages Wiki Activity Actions

Add a memory barrier to DMA functions

Browse source 
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 <benh@kernel.crashing.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Benjamin Herrenschmidt 2012-06-27 14:50:47 +10:00 • committed by Anthony Liguori
parent edded45406
commit 7a0bac4da9
2 changed files with 53 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

2
dma-helpers.c
View file

@ -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);
}