On Thu, Dec 2, 2021 at 4:55 AM David Woodhouse <dw...@infradead.org> wrote:
>
> From: David Woodhouse <d...@amazon.co.uk>
>
> By setting none of the SAGAW bits we can indicate to a guest that DMA
> translation isn't supported. Tested by booting Windows 10, as well as
> Linux guests with the fix at https://git.kernel.org/torvalds/c/c40aaaac10
>
> Signed-off-by: David Woodhouse <d...@amazon.co.uk>
> ---
> hw/i386/intel_iommu.c | 14 ++++++++++----
> include/hw/i386/intel_iommu.h | 1 +
> 2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 294499ee20..ffc852d110 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -2202,7 +2202,7 @@ static void vtd_handle_gcmd_write(IntelIOMMUState *s)
> uint32_t changed = status ^ val;
>
> trace_vtd_reg_write_gcmd(status, val);
> - if (changed & VTD_GCMD_TE) {
> + if ((changed & VTD_GCMD_TE) && s->dma_translation) {
> /* Translation enable/disable */
> vtd_handle_gcmd_te(s, val & VTD_GCMD_TE);
> }
> @@ -3100,6 +3100,7 @@ static Property vtd_properties[] = {
> DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
> DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState, scalable_mode,
> FALSE),
> DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
> + DEFINE_PROP_BOOL("dma-translation", IntelIOMMUState, dma_translation,
> true),
> DEFINE_PROP_END_OF_LIST(),
> };
>
> @@ -3605,12 +3606,17 @@ static void vtd_init(IntelIOMMUState *s)
> s->next_frcd_reg = 0;
> s->cap = VTD_CAP_FRO | VTD_CAP_NFR | VTD_CAP_ND |
> VTD_CAP_MAMV | VTD_CAP_PSI | VTD_CAP_SLLPS |
> - VTD_CAP_SAGAW_39bit | VTD_CAP_MGAW(s->aw_bits);
> + VTD_CAP_MGAW(s->aw_bits);
> if (s->dma_drain) {
> s->cap |= VTD_CAP_DRAIN;
> }
> - if (s->aw_bits == VTD_HOST_AW_48BIT) {
> - s->cap |= VTD_CAP_SAGAW_48bit;
> + if (s->dma_translation) {
> + if (s->aw_bits >= VTD_HOST_AW_39BIT) {
> + s->cap |= VTD_CAP_SAGAW_39bit;
> + }
> + if (s->aw_bits >= VTD_HOST_AW_48BIT) {
> + s->cap |= VTD_CAP_SAGAW_48bit;
> + }
> }
Just wonder if this is the hardware behaviour as I see 0 is reserved
for SAGAW in vtd 3.3 spec.
Thanks
> s->ecap = VTD_ECAP_QI | VTD_ECAP_IRO;
>
> diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> index 41783ee46d..42d6a6a636 100644
> --- a/include/hw/i386/intel_iommu.h
> +++ b/include/hw/i386/intel_iommu.h
> @@ -266,6 +266,7 @@ struct IntelIOMMUState {
> bool buggy_eim; /* Force buggy EIM unless eim=off */
> uint8_t aw_bits; /* Host/IOVA address width (in bits) */
> bool dma_drain; /* Whether DMA r/w draining enabled */
> + bool dma_translation; /* Whether DMA translation supported */
>
> /*
> * Protects IOMMU states in general. Currently it protects the
> --
> 2.31.1
>
>
