Re: [PATCH] iommu/intel: GAW only gets smaller by adding devices

Re: [PATCH] iommu/intel: GAW only gets smaller by adding devices

[Matthieu]

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Tested-by: mspeder-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org

Problem described in bug 76331 is fully solved by Alex's patch.
Could it be included in next 3.15 release ?

Thanks !

Matthieu



On Thu, May 29, 2014 at 10:23 PM, Alex Williamson <
alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:

> As analyzed in https://bugzilla.kernel.org/show_bug.cgi?id=76331
> we can have multiple DRHDs in a system and each may support different
> guest address widths.  We can add a device behind a less capable DRHD
> to a domain so long as the lesser DRHD can map the existing domain
> page table.  We should never increase the address width as a result
> of adding a device to the domain.  The current code simply updates
> the width to the last added device.  Change to keep it at the
> minumum DRHD width.
>
> Reported-by: mspeder-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Signed-off-by: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
> ---
>  drivers/iommu/intel-iommu.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index e68f44b..cd41d8d 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4276,7 +4276,7 @@ static int intel_iommu_attach_device(struct
> iommu_domain *domain,
>                        __func__, addr_width, dmar_domain->max_addr);
>                 return -EFAULT;
>         }
> -       dmar_domain->gaw = addr_width;
> +       dmar_domain->gaw = min(addr_width, dmar_domain->gaw);
>
>         /*
>          * Knock out extra levels of page tables if necessary
>
>

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[PATCH] iommu/intel: GAW only gets smaller by adding devices

[Alex Williamson]

As analyzed in https://bugzilla.kernel.org/show_bug.cgi?id=76331
we can have multiple DRHDs in a system and each may support different
guest address widths.  We can add a device behind a less capable DRHD
to a domain so long as the lesser DRHD can map the existing domain
page table.  We should never increase the address width as a result
of adding a device to the domain.  The current code simply updates
the width to the last added device.  Change to keep it at the
minumum DRHD width.

Reported-by: mspeder@users.sourceforge.net
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
---
 drivers/iommu/intel-iommu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index e68f44b..cd41d8d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4276,7 +4276,7 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 		       __func__, addr_width, dmar_domain->max_addr);
 		return -EFAULT;
 	}
-	dmar_domain->gaw = addr_width;
+	dmar_domain->gaw = min(addr_width, dmar_domain->gaw);
 
 	/*
 	 * Knock out extra levels of page tables if necessary

[PATCH] iommu/intel: GAW only gets smaller by adding devices

[Alex Williamson]

As analyzed in https://bugzilla.kernel.org/show_bug.cgi?id=76331
we can have multiple DRHDs in a system and each may support different
guest address widths.  We can add a device behind a less capable DRHD
to a domain so long as the lesser DRHD can map the existing domain
page table.  We should never increase the address width as a result
of adding a device to the domain.  The current code simply updates
the width to the last added device.  Change to keep it at the
minumum DRHD width.

Reported-by: mspeder-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Signed-off-by: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
---
 drivers/iommu/intel-iommu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index e68f44b..cd41d8d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4276,7 +4276,7 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 		       __func__, addr_width, dmar_domain->max_addr);
 		return -EFAULT;
 	}
-	dmar_domain->gaw = addr_width;
+	dmar_domain->gaw = min(addr_width, dmar_domain->gaw);
 
 	/*
 	 * Knock out extra levels of page tables if necessary