[PATCH] intel_iommu: relax iq tail check on VTD_GCMD_QIE enable

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[PATCH] intel_iommu: relax iq tail check on VTD_GCMD_QIE enable

Ladi Prosek
The VT-d spec (section 6.5.2) prescribes software to zero the
Invalidation Queue Tail Register before enabling the VTD_GCMD_QIE
Global Command Register bit. Windows Server 2012 R2 and possibly
other older Windows versions violate the protocol and set a
non-zero queue tail first, which in effect makes them crash early
on boot with -device intel-iommu,intremap=on.

This commit relaxes the check and instead of failing to enable
VTD_GCMD_QIE with "error: can't enable Queued Invalidation", it
behaves as if the tail register was set just after enabling
VTD_GCMD_QIE (see vtd_handle_iqt_write).

Signed-off-by: Ladi Prosek <[hidden email]>
---
 hw/i386/intel_iommu.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 15610b9..f2cb822 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1466,10 +1466,7 @@ static uint64_t vtd_iotlb_flush(IntelIOMMUState *s, uint64_t val)
     return iaig;
 }
 
-static inline bool vtd_queued_inv_enable_check(IntelIOMMUState *s)
-{
-    return s->iq_tail == 0;
-}
+static void vtd_fetch_inv_desc(IntelIOMMUState *s);
 
 static inline bool vtd_queued_inv_disable_check(IntelIOMMUState *s)
 {
@@ -1483,19 +1480,20 @@ static void vtd_handle_gcmd_qie(IntelIOMMUState *s, bool en)
 
     VTD_DPRINTF(INV, "Queued Invalidation Enable %s", (en ? "on" : "off"));
     if (en) {
-        if (vtd_queued_inv_enable_check(s)) {
-            s->iq = iqa_val & VTD_IQA_IQA_MASK;
-            /* 2^(x+8) entries */
-            s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
-            s->qi_enabled = true;
-            VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
-            VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
-                        s->iq, s->iq_size);
-            /* Ok - report back to driver */
-            vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
-        } else {
-            VTD_DPRINTF(GENERAL, "error: can't enable Queued Invalidation: "
-                        "tail %"PRIu16, s->iq_tail);
+        s->iq = iqa_val & VTD_IQA_IQA_MASK;
+        /* 2^(x+8) entries */
+        s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
+        s->qi_enabled = true;
+        VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
+        VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
+                    s->iq, s->iq_size);
+        /* Ok - report back to driver */
+        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
+
+        if (s->iq_tail != 0 &&
+            !(vtd_get_long_raw(s, DMAR_FSTS_REG) & VTD_FSTS_IQE)) {
+            VTD_DPRINTF(INV, "warning: QI enabled with non-zero tail");
+            vtd_fetch_inv_desc(s);
         }
     } else {
         if (vtd_queued_inv_disable_check(s)) {
--
2.9.3


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Re: [PATCH] intel_iommu: relax iq tail check on VTD_GCMD_QIE enable

Michael S. Tsirkin-4
On Fri, Jun 16, 2017 at 01:44:43PM +0200, Ladi Prosek wrote:

> The VT-d spec (section 6.5.2) prescribes software to zero the
> Invalidation Queue Tail Register before enabling the VTD_GCMD_QIE
> Global Command Register bit. Windows Server 2012 R2 and possibly
> other older Windows versions violate the protocol and set a
> non-zero queue tail first, which in effect makes them crash early
> on boot with -device intel-iommu,intremap=on.
>
> This commit relaxes the check and instead of failing to enable
> VTD_GCMD_QIE with "error: can't enable Queued Invalidation", it
> behaves as if the tail register was set just after enabling
> VTD_GCMD_QIE (see vtd_handle_iqt_write).
>
> Signed-off-by: Ladi Prosek <[hidden email]>

Thanks!
This conflicts with Peter's tracing which I merged -
could you rework on top of that pls?
the new warning should be a trace point too I imagine.

> ---
>  hw/i386/intel_iommu.c | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 15610b9..f2cb822 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1466,10 +1466,7 @@ static uint64_t vtd_iotlb_flush(IntelIOMMUState *s, uint64_t val)
>      return iaig;
>  }
>  
> -static inline bool vtd_queued_inv_enable_check(IntelIOMMUState *s)
> -{
> -    return s->iq_tail == 0;
> -}
> +static void vtd_fetch_inv_desc(IntelIOMMUState *s);
>  
>  static inline bool vtd_queued_inv_disable_check(IntelIOMMUState *s)
>  {
> @@ -1483,19 +1480,20 @@ static void vtd_handle_gcmd_qie(IntelIOMMUState *s, bool en)
>  
>      VTD_DPRINTF(INV, "Queued Invalidation Enable %s", (en ? "on" : "off"));
>      if (en) {
> -        if (vtd_queued_inv_enable_check(s)) {
> -            s->iq = iqa_val & VTD_IQA_IQA_MASK;
> -            /* 2^(x+8) entries */
> -            s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
> -            s->qi_enabled = true;
> -            VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
> -            VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
> -                        s->iq, s->iq_size);
> -            /* Ok - report back to driver */
> -            vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
> -        } else {
> -            VTD_DPRINTF(GENERAL, "error: can't enable Queued Invalidation: "
> -                        "tail %"PRIu16, s->iq_tail);
> +        s->iq = iqa_val & VTD_IQA_IQA_MASK;
> +        /* 2^(x+8) entries */
> +        s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
> +        s->qi_enabled = true;
> +        VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
> +        VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
> +                    s->iq, s->iq_size);
> +        /* Ok - report back to driver */
> +        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
> +
> +        if (s->iq_tail != 0 &&
> +            !(vtd_get_long_raw(s, DMAR_FSTS_REG) & VTD_FSTS_IQE)) {
> +            VTD_DPRINTF(INV, "warning: QI enabled with non-zero tail");
> +            vtd_fetch_inv_desc(s);
>          }
>      } else {
>          if (vtd_queued_inv_disable_check(s)) {
> --
> 2.9.3

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Re: [PATCH] intel_iommu: relax iq tail check on VTD_GCMD_QIE enable

Peter Xu
In reply to this post by Ladi Prosek
On Fri, Jun 16, 2017 at 01:44:43PM +0200, Ladi Prosek wrote:

> The VT-d spec (section 6.5.2) prescribes software to zero the
> Invalidation Queue Tail Register before enabling the VTD_GCMD_QIE
> Global Command Register bit. Windows Server 2012 R2 and possibly
> other older Windows versions violate the protocol and set a
> non-zero queue tail first, which in effect makes them crash early
> on boot with -device intel-iommu,intremap=on.
>
> This commit relaxes the check and instead of failing to enable
> VTD_GCMD_QIE with "error: can't enable Queued Invalidation", it
> behaves as if the tail register was set just after enabling
> VTD_GCMD_QIE (see vtd_handle_iqt_write).
>
> Signed-off-by: Ladi Prosek <[hidden email]>
> ---
>  hw/i386/intel_iommu.c | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 15610b9..f2cb822 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1466,10 +1466,7 @@ static uint64_t vtd_iotlb_flush(IntelIOMMUState *s, uint64_t val)
>      return iaig;
>  }
>  
> -static inline bool vtd_queued_inv_enable_check(IntelIOMMUState *s)
> -{
> -    return s->iq_tail == 0;
> -}
> +static void vtd_fetch_inv_desc(IntelIOMMUState *s);
>  
>  static inline bool vtd_queued_inv_disable_check(IntelIOMMUState *s)
>  {
> @@ -1483,19 +1480,20 @@ static void vtd_handle_gcmd_qie(IntelIOMMUState *s, bool en)
>  
>      VTD_DPRINTF(INV, "Queued Invalidation Enable %s", (en ? "on" : "off"));
>      if (en) {
> -        if (vtd_queued_inv_enable_check(s)) {
> -            s->iq = iqa_val & VTD_IQA_IQA_MASK;
> -            /* 2^(x+8) entries */
> -            s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
> -            s->qi_enabled = true;
> -            VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
> -            VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
> -                        s->iq, s->iq_size);
> -            /* Ok - report back to driver */
> -            vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
> -        } else {
> -            VTD_DPRINTF(GENERAL, "error: can't enable Queued Invalidation: "
> -                        "tail %"PRIu16, s->iq_tail);
> +        s->iq = iqa_val & VTD_IQA_IQA_MASK;
> +        /* 2^(x+8) entries */
> +        s->iq_size = 1UL << ((iqa_val & VTD_IQA_QS) + 8);
> +        s->qi_enabled = true;
> +        VTD_DPRINTF(INV, "DMAR_IQA_REG 0x%"PRIx64, iqa_val);
> +        VTD_DPRINTF(INV, "Invalidation Queue addr 0x%"PRIx64 " size %d",
> +                    s->iq, s->iq_size);
> +        /* Ok - report back to driver */
> +        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_QIES);
> +
> +        if (s->iq_tail != 0 &&
> +            !(vtd_get_long_raw(s, DMAR_FSTS_REG) & VTD_FSTS_IQE)) {
> +            VTD_DPRINTF(INV, "warning: QI enabled with non-zero tail");
> +            vtd_fetch_inv_desc(s);

Since looks like we need another post, a tiny suggestion is that we
can also add some comment to tell the reason why we didn't really
check it, and a trace_vtd_warn_invalid_qi_tail() tracer to show that
spec is violated (if you see, we have two other warnings already named
vtd_warn_ir_* which also helps on tracing spec violations).

I'll ack the next version after it's cooked. Thanks Ladi for the
patch!

Peter

>          }
>      } else {
>          if (vtd_queued_inv_disable_check(s)) {
> --
> 2.9.3
>

--
Peter Xu

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Re: [PATCH] intel_iommu: relax iq tail check on VTD_GCMD_QIE enable

Ladi Prosek
On Mon, Jun 19, 2017 at 8:42 AM, Peter Xu <[hidden email]> wrote:
> Since looks like we need another post, a tiny suggestion is that we
> can also add some comment to tell the reason why we didn't really
> check it, and a trace_vtd_warn_invalid_qi_tail() tracer to show that
> spec is violated (if you see, we have two other warnings already named
> vtd_warn_ir_* which also helps on tracing spec violations).

Sure thing, I've just sent v2 with trace_vtd_warn_invalid_qi_tail and a comment.

> I'll ack the next version after it's cooked. Thanks Ladi for the
> patch!

Thanks!
Ladi

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