Soon, IOMMU drivers running in the hypervisor might interact with
non-coherent devices, so it needs a mechanism to map memory as
non cacheable.
Add ___pkvm_host_donate_hyp() which accepts a new argument for prot,
so the driver can add KVM_PGTABLE_PROT_NORMAL_NC.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index 5f9d56754e39..52d7ee91e18c 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -36,6 +36,7 @@ int __pkvm_prot_finalize(void);
 int __pkvm_host_share_hyp(u64 pfn);
 int __pkvm_host_unshare_hyp(u64 pfn);
 int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
+int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot);
 int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
 int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
 int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 8957734d6183..861e448183fd 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -769,13 +769,15 @@ int __pkvm_host_unshare_hyp(u64 pfn)
 	return ret;
 }
 
-int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
+int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot)
 {
 	u64 phys = hyp_pfn_to_phys(pfn);
 	u64 size = PAGE_SIZE * nr_pages;
 	void *virt = __hyp_va(phys);
 	int ret;
 
+	WARN_ON(prot & KVM_PGTABLE_PROT_X);
+
 	host_lock_component();
 	hyp_lock_component();
 
@@ -787,7 +789,7 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
 		goto unlock;
 
 	__hyp_set_page_state_range(phys, size, PKVM_PAGE_OWNED);
-	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, PAGE_HYP));
+	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, prot));
 	WARN_ON(host_stage2_set_owner_locked(phys, size, PKVM_ID_HYP));
 
 unlock:
@@ -797,6 +799,11 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
 	return ret;
 }
 
+int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
+{
+	return ___pkvm_host_donate_hyp(pfn, nr_pages, PAGE_HYP);
+}
+
 int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages)
 {
 	u64 phys = hyp_pfn_to_phys(pfn);
-- 
2.51.0.rc1.167.g924127e9c0-goog

On Tue, Aug 19, 2025 at 09:51:29PM +0000, Mostafa Saleh wrote:
> Soon, IOMMU drivers running in the hypervisor might interact with
> non-coherent devices, so it needs a mechanism to map memory as
> non cacheable.
> Add ___pkvm_host_donate_hyp() which accepts a new argument for prot,
> so the driver can add KVM_PGTABLE_PROT_NORMAL_NC.
> 
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> ---
>  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++++++++--
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> index 5f9d56754e39..52d7ee91e18c 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> @@ -36,6 +36,7 @@ int __pkvm_prot_finalize(void);
>  int __pkvm_host_share_hyp(u64 pfn);
>  int __pkvm_host_unshare_hyp(u64 pfn);
>  int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
> +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot);
>  int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
>  int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
>  int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 8957734d6183..861e448183fd 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -769,13 +769,15 @@ int __pkvm_host_unshare_hyp(u64 pfn)
>  	return ret;
>  }
>  
> -int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
> +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot)
>  {
>  	u64 phys = hyp_pfn_to_phys(pfn);
>  	u64 size = PAGE_SIZE * nr_pages;
>  	void *virt = __hyp_va(phys);
>  	int ret;
>  
> +	WARN_ON(prot & KVM_PGTABLE_PROT_X);

Should this actually just enforce that the permissions are
KVM_PGTABLE_PROT_RW:

	WARN_ON((prot & KVM_PGTABLE_PROT_RWX) != KVM_PGTABLE_PROT_RW);

?

Since the motivation is about the memory type rather than the
permissions, it would be best to preserve the current behaviour.

Will

On Tue, Sep 09, 2025 at 02:46:42PM +0100, Will Deacon wrote:
> On Tue, Aug 19, 2025 at 09:51:29PM +0000, Mostafa Saleh wrote:
> > Soon, IOMMU drivers running in the hypervisor might interact with
> > non-coherent devices, so it needs a mechanism to map memory as
> > non cacheable.
> > Add ___pkvm_host_donate_hyp() which accepts a new argument for prot,
> > so the driver can add KVM_PGTABLE_PROT_NORMAL_NC.
> > 
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
> >  arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++++++++--
> >  2 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > index 5f9d56754e39..52d7ee91e18c 100644
> > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > @@ -36,6 +36,7 @@ int __pkvm_prot_finalize(void);
> >  int __pkvm_host_share_hyp(u64 pfn);
> >  int __pkvm_host_unshare_hyp(u64 pfn);
> >  int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
> > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot);
> >  int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
> >  int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
> >  int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > index 8957734d6183..861e448183fd 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > @@ -769,13 +769,15 @@ int __pkvm_host_unshare_hyp(u64 pfn)
> >  	return ret;
> >  }
> >  
> > -int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
> > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot)
> >  {
> >  	u64 phys = hyp_pfn_to_phys(pfn);
> >  	u64 size = PAGE_SIZE * nr_pages;
> >  	void *virt = __hyp_va(phys);
> >  	int ret;
> >  
> > +	WARN_ON(prot & KVM_PGTABLE_PROT_X);
> 
> Should this actually just enforce that the permissions are
> KVM_PGTABLE_PROT_RW:
> 
> 	WARN_ON((prot & KVM_PGTABLE_PROT_RWX) != KVM_PGTABLE_PROT_RW);
> 
> ?
> 
> Since the motivation is about the memory type rather than the
> permissions, it would be best to preserve the current behaviour.

Yes, this series doesn't do any permisson changes, I was not sure if
that would be needed in the future or not (some RO mappings), but I will
update the check as suggested to be more strict.

Thanks,
Mostafa

> 
> Will

On Tue, Sep 09, 2025 at 02:46:42PM +0100, Will Deacon wrote:
> On Tue, Aug 19, 2025 at 09:51:29PM +0000, Mostafa Saleh wrote:
> > Soon, IOMMU drivers running in the hypervisor might interact with
> > non-coherent devices, so it needs a mechanism to map memory as
> > non cacheable.
> > Add ___pkvm_host_donate_hyp() which accepts a new argument for prot,
> > so the driver can add KVM_PGTABLE_PROT_NORMAL_NC.
> > 
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
> >  arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++++++++--
> >  2 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > index 5f9d56754e39..52d7ee91e18c 100644
> > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > @@ -36,6 +36,7 @@ int __pkvm_prot_finalize(void);
> >  int __pkvm_host_share_hyp(u64 pfn);
> >  int __pkvm_host_unshare_hyp(u64 pfn);
> >  int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
> > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot);
> >  int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
> >  int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
> >  int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > index 8957734d6183..861e448183fd 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > @@ -769,13 +769,15 @@ int __pkvm_host_unshare_hyp(u64 pfn)
> >  	return ret;
> >  }
> >  
> > -int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
> > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot)
> >  {
> >  	u64 phys = hyp_pfn_to_phys(pfn);
> >  	u64 size = PAGE_SIZE * nr_pages;
> >  	void *virt = __hyp_va(phys);
> >  	int ret;
> >  
> > +	WARN_ON(prot & KVM_PGTABLE_PROT_X);
> 
> Should this actually just enforce that the permissions are
> KVM_PGTABLE_PROT_RW:
> 
> 	WARN_ON((prot & KVM_PGTABLE_PROT_RWX) != KVM_PGTABLE_PROT_RW);
> 
> ?
> 
> Since the motivation is about the memory type rather than the
> permissions, it would be best to preserve the current behaviour.

+1. I believe the current `WARN_ON(prot & KVM_PGTABLE_PROT_X);` check
would potentially allow "Read-only" or "Write-only" donations to slide
through silently.

> 
> Will

Thanks,
Praan

On Sun, Sep 14, 2025 at 07:23:12PM +0000, Pranjal Shrivastava wrote:
> On Tue, Sep 09, 2025 at 02:46:42PM +0100, Will Deacon wrote:
> > On Tue, Aug 19, 2025 at 09:51:29PM +0000, Mostafa Saleh wrote:
> > > Soon, IOMMU drivers running in the hypervisor might interact with
> > > non-coherent devices, so it needs a mechanism to map memory as
> > > non cacheable.
> > > Add ___pkvm_host_donate_hyp() which accepts a new argument for prot,
> > > so the driver can add KVM_PGTABLE_PROT_NORMAL_NC.
> > > 
> > > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > > ---
> > >  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
> > >  arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++++++++--
> > >  2 files changed, 10 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > > index 5f9d56754e39..52d7ee91e18c 100644
> > > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> > > @@ -36,6 +36,7 @@ int __pkvm_prot_finalize(void);
> > >  int __pkvm_host_share_hyp(u64 pfn);
> > >  int __pkvm_host_unshare_hyp(u64 pfn);
> > >  int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
> > > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot);
> > >  int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
> > >  int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
> > >  int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
> > > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > > index 8957734d6183..861e448183fd 100644
> > > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > > @@ -769,13 +769,15 @@ int __pkvm_host_unshare_hyp(u64 pfn)
> > >  	return ret;
> > >  }
> > >  
> > > -int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
> > > +int ___pkvm_host_donate_hyp(u64 pfn, u64 nr_pages, enum kvm_pgtable_prot prot)
> > >  {
> > >  	u64 phys = hyp_pfn_to_phys(pfn);
> > >  	u64 size = PAGE_SIZE * nr_pages;
> > >  	void *virt = __hyp_va(phys);
> > >  	int ret;
> > >  
> > > +	WARN_ON(prot & KVM_PGTABLE_PROT_X);
> > 
> > Should this actually just enforce that the permissions are
> > KVM_PGTABLE_PROT_RW:
> > 
> > 	WARN_ON((prot & KVM_PGTABLE_PROT_RWX) != KVM_PGTABLE_PROT_RW);
> > 
> > ?
> > 
> > Since the motivation is about the memory type rather than the
> > permissions, it would be best to preserve the current behaviour.
> 
> +1. I believe the current `WARN_ON(prot & KVM_PGTABLE_PROT_X);` check
> would potentially allow "Read-only" or "Write-only" donations to slide
> through silently.

True, this can only be done from the hypervisor code though, I will
make the check stricter as Will suggested, and if needed we can relax
that later.

Thanks,
Mostafa

> 
> > 
> > Will
> 
> Thanks,
> Praan