diff mbox series

[v2,2/4] intel_iommu: Support IR-only mode without DMA translation

Message ID 20211209220840.14889-2-dwmw2@infradead.org (mailing list archive)
State New, archived
Headers show
Series [v2,1/4] target/i386: Fix sanity check on max APIC ID / X2APIC enablement | expand

Commit Message

David Woodhouse Dec. 9, 2021, 10:08 p.m. UTC 
From: David Woodhouse <dwmw@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 <dwmw@amazon.co.uk>
Acked-by: Claudio Fontana <cfontana@suse.de>
---
 hw/i386/intel_iommu.c         | 14 ++++++++++----
 include/hw/i386/intel_iommu.h |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

Comments

Peter Xu Dec. 16, 2021, 8:47 a.m. UTC | #1 
On Thu, Dec 09, 2021 at 10:08:38PM +0000, David Woodhouse wrote:
> From: David Woodhouse <dwmw@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 <dwmw@amazon.co.uk>
> Acked-by: Claudio Fontana <cfontana@suse.de>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index f584449d8d..9a3cb2b789 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;
+            }
     }
     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