(2013/04/20 15:58), Wei Hu wrote:
> On a VT-d capable machine Linux will enable IOMMU by default. If it
> then kexec's a second kernel with intel_iommu=off, this second kernel
> will leave the DMA remapping engine on with no code handling it. The
> symptom is at least USB and SATA drives stop working. This patch fixes
> the problem by always disabling DMA remapping when intel_iommu=off.
Even when second kernel boots up with intel_iommu=on, dma-remapping need
to be disabled as well before it is initialized and enabled again in
init_dmars(). So, how about something like this?
for_each_drhd_unit(drhd) {
struct dmar_drhd_unit *drhd;
if (drhd->ignored)
continue;
iommu = drhd->iommu;
if (iommu->gcmd & DMA_GCMD_TE)
iommu_disable_translation(iommu);
}
Note, if you agree above code and fix your patch like this, you need
additinal fix to set iommu->gcmd flag sinse gcmd is always zero here.
See first hunk of this patch.
https://lkml.org/lkml/2013/3/20/707
Thanks,
Takao Indoh
>
> Signed-off-by: Wei Hu <[email protected]>
> ---
> drivers/iommu/intel-iommu.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 0099667..0b8f8bb 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3681,8 +3681,12 @@ int __init intel_iommu_init(void)
> return -ENODEV;
> }
>
> - if (no_iommu || dmar_disabled)
> + if (no_iommu || dmar_disabled) {
> + struct dmar_drhd_unit *drhd;
> + for_each_drhd_unit(drhd)
> + iommu_disable_translation(drhd->iommu);
> return -ENODEV;
> + }
>
> if (iommu_init_mempool()) {
> if (force_on)
>
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