Messages in this thread | | | From | Thiago Jung Bauermann <> | Subject | Re: [RFC PATCH 10/11] powerpc/svm: Force the use of bounce buffers | Date | Fri, 24 Aug 2018 20:38:54 -0300 |
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Hello Christoph,
Thanks for your quick review.
Christoph Hellwig <hch@lst.de> writes:
> On Thu, Aug 23, 2018 at 11:59:32PM -0300, Thiago Jung Bauermann wrote: >> From: Anshuman Khandual <khandual@linux.vnet.ibm.com> >> >> SWIOTLB checks range of incoming CPU addresses to be bounced and see if the >> device can access it through it's DMA window without requiring bouncing. In >> such cases it just chooses to skip bouncing. But for cases like secure >> guests on powerpc platform all addresses need to be bounced into the shared >> pool of memory because the host cannot access it otherwise. Hence the need >> to do the bouncing is not related to device's DMA window. Hence force the >> use of bouncing by setting the swiotlb_force variable on secure guests. >> >> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> >> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com> >> --- >> arch/powerpc/kernel/svm.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/powerpc/kernel/svm.c b/arch/powerpc/kernel/svm.c >> index 1af5caa955f5..f0576ad65cd0 100644 >> --- a/arch/powerpc/kernel/svm.c >> +++ b/arch/powerpc/kernel/svm.c >> @@ -17,6 +17,7 @@ static int __init init_svm(void) >> return 0; >> >> ppc_swiotlb_enable = 1; >> + swiotlb_force = SWIOTLB_FORCE; >> swiotlb_update_mem_attributes(); > > This needs a comment.
Good point. Will add one.
If in the new scheme of things (with bus_dma_mask?) dma_capable() on a virtio device running in a secure guest returns false, then this patch becomes unnecessary and can be dropped.
-- Thiago Jung Bauermann IBM Linux Technology Center
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