Add a file only compiled for KVM mode.

At the moment it registers the driver with KVM, and add the hook
needed for memory allocation.

Next, it will create the array with available SMMUs and their
description.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 arch/arm64/include/asm/kvm_host.h             |  4 +++
 arch/arm64/kvm/iommu.c                        | 10 ++++--
 drivers/iommu/arm/arm-smmu-v3/Makefile        |  1 +
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 36 +++++++++++++++++++
 4 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index fcb4b26072f7..52212c0f2e9c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1678,4 +1678,8 @@ struct kvm_iommu_ops;
 int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops);
 size_t kvm_iommu_pages(void);
 
+#ifdef CONFIG_ARM_SMMU_V3_PKVM
+size_t smmu_hyp_pgt_pages(void);
+#endif
+
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/iommu.c b/arch/arm64/kvm/iommu.c
index 5460b1bd44a6..0475f7c95c6c 100644
--- a/arch/arm64/kvm/iommu.c
+++ b/arch/arm64/kvm/iommu.c
@@ -17,10 +17,16 @@ int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops)
 
 size_t kvm_iommu_pages(void)
 {
+	size_t nr_pages = 0;
+
 	/*
 	 * This is called very early during setup_arch() where no initcalls,
 	 * so this has to call specific functions per each KVM driver.
 	 */
-	kvm_nvhe_sym(hyp_kvm_iommu_pages) = 0;
-	return 0;
+#ifdef CONFIG_ARM_SMMU_V3_PKVM
+	nr_pages = smmu_hyp_pgt_pages();
+#endif
+
+	kvm_nvhe_sym(hyp_kvm_iommu_pages) = nr_pages;
+	return nr_pages;
 }
diff --git a/drivers/iommu/arm/arm-smmu-v3/Makefile b/drivers/iommu/arm/arm-smmu-v3/Makefile
index 1918b4a64cb0..284ad71c5282 100644
--- a/drivers/iommu/arm/arm-smmu-v3/Makefile
+++ b/drivers/iommu/arm/arm-smmu-v3/Makefile
@@ -4,5 +4,6 @@ arm_smmu_v3-y := arm-smmu-v3.o arm-smmu-v3-common-hyp.o
 arm_smmu_v3-$(CONFIG_ARM_SMMU_V3_IOMMUFD) += arm-smmu-v3-iommufd.o
 arm_smmu_v3-$(CONFIG_ARM_SMMU_V3_SVA) += arm-smmu-v3-sva.o
 arm_smmu_v3-$(CONFIG_TEGRA241_CMDQV) += tegra241-cmdqv.o
+arm_smmu_v3-$(CONFIG_ARM_SMMU_V3_PKVM) += arm-smmu-v3-kvm.o
 
 obj-$(CONFIG_ARM_SMMU_V3_KUNIT_TEST) += arm-smmu-v3-test.o
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
new file mode 100644
index 000000000000..ac4eac6d567f
--- /dev/null
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * pKVM host driver for the Arm SMMUv3
+ *
+ * Copyright (C) 2022 Linaro Ltd.
+ */
+#include <asm/kvm_mmu.h>
+#include <asm/kvm_pkvm.h>
+
+#include <linux/of_platform.h>
+
+#include "arm-smmu-v3.h"
+#include "pkvm/arm_smmu_v3.h"
+
+extern struct kvm_iommu_ops kvm_nvhe_sym(smmu_ops);
+
+size_t smmu_hyp_pgt_pages(void)
+{
+	/*
+	 * SMMUv3 uses the same format as stage-2 and hence have the same memory
+	 * requirements, we add extra 500 pages for L2 ste.
+	 */
+	if (of_find_compatible_node(NULL, NULL, "arm,smmu-v3"))
+		return host_s2_pgtable_pages() + 500;
+	return 0;
+}
+
+static int kvm_arm_smmu_v3_register(void)
+{
+	if (!is_protected_kvm_enabled())
+		return 0;
+
+	return kvm_iommu_register_driver(kern_hyp_va(lm_alias(&kvm_nvhe_sym(smmu_ops))));
+};
+
+core_initcall(kvm_arm_smmu_v3_register);
-- 
2.51.0.rc1.167.g924127e9c0-goog

On Tue, Aug 19, 2025 at 09:51:42PM +0000, Mostafa Saleh wrote:
> Add a file only compiled for KVM mode.
> 
> At the moment it registers the driver with KVM, and add the hook
> needed for memory allocation.
> 
> Next, it will create the array with available SMMUs and their
> description.
> 
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> ---
>  arch/arm64/include/asm/kvm_host.h             |  4 +++
>  arch/arm64/kvm/iommu.c                        | 10 ++++--
>  drivers/iommu/arm/arm-smmu-v3/Makefile        |  1 +
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 36 +++++++++++++++++++
>  4 files changed, 49 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index fcb4b26072f7..52212c0f2e9c 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -1678,4 +1678,8 @@ struct kvm_iommu_ops;
>  int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops);
>  size_t kvm_iommu_pages(void);
>  
> +#ifdef CONFIG_ARM_SMMU_V3_PKVM
> +size_t smmu_hyp_pgt_pages(void);
> +#endif
> +
>  #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/kvm/iommu.c b/arch/arm64/kvm/iommu.c
> index 5460b1bd44a6..0475f7c95c6c 100644
> --- a/arch/arm64/kvm/iommu.c
> +++ b/arch/arm64/kvm/iommu.c
> @@ -17,10 +17,16 @@ int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops)
>  
>  size_t kvm_iommu_pages(void)
>  {
> +	size_t nr_pages = 0;
> +
>  	/*
>  	 * This is called very early during setup_arch() where no initcalls,
>  	 * so this has to call specific functions per each KVM driver.
>  	 */
> -	kvm_nvhe_sym(hyp_kvm_iommu_pages) = 0;
> -	return 0;
> +#ifdef CONFIG_ARM_SMMU_V3_PKVM
> +	nr_pages = smmu_hyp_pgt_pages();
> +#endif

Rather than hard-code this here, I wonder whether it would be better to
have a default size for the IOMMU carveout and have the driver tells us
how much it needs later on when it probes. Then we could either free
any unused portion back to the host or return an error to the driver if
it wants more than we have.

Will

On Fri, Sep 12, 2025 at 02:52:27PM +0100, Will Deacon wrote:
> On Tue, Aug 19, 2025 at 09:51:42PM +0000, Mostafa Saleh wrote:
> > Add a file only compiled for KVM mode.
> > 
> > At the moment it registers the driver with KVM, and add the hook
> > needed for memory allocation.
> > 
> > Next, it will create the array with available SMMUs and their
> > description.
> > 
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  arch/arm64/include/asm/kvm_host.h             |  4 +++
> >  arch/arm64/kvm/iommu.c                        | 10 ++++--
> >  drivers/iommu/arm/arm-smmu-v3/Makefile        |  1 +
> >  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 36 +++++++++++++++++++
> >  4 files changed, 49 insertions(+), 2 deletions(-)
> >  create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
> > 
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index fcb4b26072f7..52212c0f2e9c 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -1678,4 +1678,8 @@ struct kvm_iommu_ops;
> >  int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops);
> >  size_t kvm_iommu_pages(void);
> >  
> > +#ifdef CONFIG_ARM_SMMU_V3_PKVM
> > +size_t smmu_hyp_pgt_pages(void);
> > +#endif
> > +
> >  #endif /* __ARM64_KVM_HOST_H__ */
> > diff --git a/arch/arm64/kvm/iommu.c b/arch/arm64/kvm/iommu.c
> > index 5460b1bd44a6..0475f7c95c6c 100644
> > --- a/arch/arm64/kvm/iommu.c
> > +++ b/arch/arm64/kvm/iommu.c
> > @@ -17,10 +17,16 @@ int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops)
> >  
> >  size_t kvm_iommu_pages(void)
> >  {
> > +	size_t nr_pages = 0;
> > +
> >  	/*
> >  	 * This is called very early during setup_arch() where no initcalls,
> >  	 * so this has to call specific functions per each KVM driver.
> >  	 */
> > -	kvm_nvhe_sym(hyp_kvm_iommu_pages) = 0;
> > -	return 0;
> > +#ifdef CONFIG_ARM_SMMU_V3_PKVM
> > +	nr_pages = smmu_hyp_pgt_pages();
> > +#endif
> 
> Rather than hard-code this here, I wonder whether it would be better to
> have a default size for the IOMMU carveout and have the driver tells us
> how much it needs later on when it probes. Then we could either free
> any unused portion back to the host or return an error to the driver if
> it wants more than we have.

I can do that, we can set the default from a config or cmdline (or
both).

Thanks,
Mostafa

> 
> Will
>