The IOMMU driver calculates the guest addressability for a DMA request
based on the value of the mgaw reported from the IOMMU. However, this
is a fused value and as mentioned in the spec, the guest width
should be calculated based on the supported adjusted guest address width
(SAGAW).
This is from specification:
"Guest addressability for a given DMA request is limited to the
minimum of the value reported through this field and the adjusted
guest address width of the corresponding page-table structure.
(Adjusted guest address widths supported by hardware are reported
through the SAGAW field)."
This causes domain initialization to fail and following
errors appear for EHCI PCI driver:
[ 2.486393] ehci-pci 0000:01:00.4: EHCI Host Controller
[ 2.486624] ehci-pci 0000:01:00.4: new USB bus registered, assigned bus
number 1
[ 2.489127] ehci-pci 0000:01:00.4: DMAR: Allocating domain failed
[ 2.489350] ehci-pci 0000:01:00.4: DMAR: 32bit DMA uses non-identity
mapping
[ 2.489359] ehci-pci 0000:01:00.4: can't setup: -12
[ 2.489531] ehci-pci 0000:01:00.4: USB bus 1 deregistered
[ 2.490023] ehci-pci 0000:01:00.4: init 0000:01:00.4 fail, -12
[ 2.490358] ehci-pci: probe of 0000:01:00.4 failed with error -12
This issue happens when the value of the sagaw corresponds to a
48-bit agaw. This fix updates the calculation of the agaw based on
the IOMMU's sagaw value.
Signed-off-by: Saeed Mirzamohammadi <[email protected]>
Tested-by: Camille Lu <[email protected]>
---
drivers/iommu/intel-iommu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 953d86ca6d2b..396e14fad54b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1867,8 +1867,8 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu,
domain_reserve_special_ranges(domain);
/* calculate AGAW */
- if (guest_width > cap_mgaw(iommu->cap))
- guest_width = cap_mgaw(iommu->cap);
+ if (guest_width > agaw_to_width(iommu->agaw))
+ guest_width = agaw_to_width(iommu->agaw);
domain->gaw = guest_width;
adjust_width = guestwidth_to_adjustwidth(guest_width);
agaw = width_to_agaw(adjust_width);
--
2.27.0
Hi Saeed,
On 4/7/21 12:35 AM, Saeed Mirzamohammadi wrote:
> The IOMMU driver calculates the guest addressability for a DMA request
> based on the value of the mgaw reported from the IOMMU. However, this
> is a fused value and as mentioned in the spec, the guest width
> should be calculated based on the supported adjusted guest address width
> (SAGAW).
>
> This is from specification:
> "Guest addressability for a given DMA request is limited to the
> minimum of the value reported through this field and the adjusted
> guest address width of the corresponding page-table structure.
> (Adjusted guest address widths supported by hardware are reported
> through the SAGAW field)."
>
> This causes domain initialization to fail and following
> errors appear for EHCI PCI driver:
>
> [ 2.486393] ehci-pci 0000:01:00.4: EHCI Host Controller
> [ 2.486624] ehci-pci 0000:01:00.4: new USB bus registered, assigned bus
> number 1
> [ 2.489127] ehci-pci 0000:01:00.4: DMAR: Allocating domain failed
> [ 2.489350] ehci-pci 0000:01:00.4: DMAR: 32bit DMA uses non-identity
> mapping
> [ 2.489359] ehci-pci 0000:01:00.4: can't setup: -12
> [ 2.489531] ehci-pci 0000:01:00.4: USB bus 1 deregistered
> [ 2.490023] ehci-pci 0000:01:00.4: init 0000:01:00.4 fail, -12
> [ 2.490358] ehci-pci: probe of 0000:01:00.4 failed with error -12
>
> This issue happens when the value of the sagaw corresponds to a
> 48-bit agaw. This fix updates the calculation of the agaw based on
> the IOMMU's sagaw value.
>
> Signed-off-by: Saeed Mirzamohammadi <[email protected]>
> Tested-by: Camille Lu <[email protected]>
> ---
> drivers/iommu/intel-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 953d86ca6d2b..396e14fad54b 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1867,8 +1867,8 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu,
> domain_reserve_special_ranges(domain);
>
> /* calculate AGAW */
> - if (guest_width > cap_mgaw(iommu->cap))
> - guest_width = cap_mgaw(iommu->cap);
> + if (guest_width > agaw_to_width(iommu->agaw))
> + guest_width = agaw_to_width(iommu->agaw);
The spec requires to use a minimum of MGAW and AGAW, so why not,
cap_width = min_t(int, cap_mgaw(iommu->cap), agaw_to_width(iommu->agaw));
if (guest_width > cap_width)
guest_width = cap_width;
Best regards,
baolu
> domain->gaw = guest_width;
> adjust_width = guestwidth_to_adjustwidth(guest_width);
> agaw = width_to_agaw(adjust_width);
>