Re: [PATCH 03/24] iommu/amd: Detect and initialize AMD vIOMMU feature

[Suthikulpanit, Suravee]

Hi

On 8/10/2026 3:13 PM, Vasant Hegde wrote:
> .../...
> >   }
> >   
> >   static int __init amd_iommu_init_pci(void)
> > diff --git a/drivers/iommu/amd/viommu.c b/drivers/iommu/amd/viommu.c
> > new file mode 100644
> > index 000000000000..f4b5f96d4785
> > --- /dev/null
> > +++ b/drivers/iommu/amd/viommu.c
> > @@ -0,0 +1,29 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2023 Advanced Micro Devices, Inc.
> > + */
> > +
> > +#define pr_fmt(fmt)     "AMD-Vi: " fmt
> > +#define dev_fmt(fmt)    pr_fmt(fmt)
> > +
> > +#include <linux/iommu.h>
> > +#include <linux/iommufd.h>
> > +#include <linux/amd-iommu.h>
> > +#include <uapi/linux/iommufd.h>
> > +
> > +#include <asm/iommu.h>
> > +#include <asm/set_memory.h>
> > +
> > +#include "iommufd.h"
> > +#include "amd_iommu.h"
> > +#include "amd_iommu_types.h"
> > +#include "amd_viommu.h"
> > +
> > +int __init amd_viommu_init(struct amd_iommu *iommu)
> > +{
> > +	if (!amd_iommu_viommu ||
> > +	    !check_feature(FEATURE_VIOMMU))
>
> If check_feature returns false, then return -ENOSUPPORT so that called sets
> amd_iommu_viommu to false.

Actually, that would print "Failed to initialize vIOMMU" in dmesg on 
older systems, which does not support the feature. We don't want that.

For v5, I will clean up this logic to make sure that the 
amd_iommu_viommu is false when the feature is not supporte.

> Also how about renaming it as "amd_iommu_viommu_present" ? Because following
> patches defines another structure with same name. It works, but add confusion.

I'll change this to amd_iommu_viommu_enabled in v5

Thanks,
Suravee

> -Vasant