[PATCH v4 0/2] mm: add vmalloc_no_huge and use it

[PATCH v4 0/2] mm: add vmalloc_no_huge and use it

[Claudio Imbrenda]

Add vmalloc_no_huge and export it, so modules can allocate memory with
small pages.

Use the newly added vmalloc_no_huge in KVM on s390 to get around a
hardware limitation.

v3->v4:
* reword commit messages to be more clear
* add comment in the second patch

v2->v3:
* do not export __vmalloc_node_range
* add vmalloc_no_huge as a wrapper around __vmalloc_node_range
* use vmalloc_no_huge instead of __vmalloc_node_range in kvm on s390x

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Hellwig <hch@infradead.org>

Claudio Imbrenda (2):
  mm/vmalloc: add vmalloc_no_huge
  KVM: s390: prepare for hugepage vmalloc

 arch/s390/kvm/pv.c      |  7 ++++++-
 include/linux/vmalloc.h |  1 +
 mm/vmalloc.c            | 16 ++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

-- 
2.31.1

[PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge

[Claudio Imbrenda]

Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
support for hugepage vmalloc mappings, it also added the flag
VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to
be performed with 0-order non-huge pages.  This flag is not accessible
when calling vmalloc, the only option is to call directly
__vmalloc_node_range, which is not exported.

This means that a module can't vmalloc memory with small pages.

Case in point: KVM on s390x needs to vmalloc a large area, and it needs
to be mapped with non-huge pages, because of a hardware limitation.

This patch adds the function vmalloc_no_huge, which works like vmalloc,
but it is guaranteed to always back the mapping using small pages. This
new function is exported, therefore it is usable by modules.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
---
 include/linux/vmalloc.h |  1 +
 mm/vmalloc.c            | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 4d668abb6391..bfaaf0b6fa76 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
 			const void *caller);
 void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
 		int node, const void *caller);
+void *vmalloc_no_huge(unsigned long size);
 
 extern void vfree(const void *addr);
 extern void vfree_atomic(const void *addr);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a13ac524f6ff..296a2fcc3fbe 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size)
 }
 EXPORT_SYMBOL(vmalloc);
 
+/**
+ * vmalloc_no_huge - allocate virtually contiguous memory using small pages
+ * @size:    allocation size
+ *
+ * Allocate enough non-huge pages to cover @size from the page level
+ * allocator and map them into contiguous kernel virtual space.
+ *
+ * Return: pointer to the allocated memory or %NULL on error
+ */
+void *vmalloc_no_huge(unsigned long size)
+{
+	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
+				    VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));
+}
+EXPORT_SYMBOL(vmalloc_no_huge);
+
 /**
  * vzalloc - allocate virtually contiguous memory with zero fill
  * @size:    allocation size
-- 
2.31.1

Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge

[David Hildenbrand]

On 14.06.21 15:23, Claudio Imbrenda wrote:
> Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
> support for hugepage vmalloc mappings, it also added the flag
> VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to
> be performed with 0-order non-huge pages.  This flag is not accessible
> when calling vmalloc, the only option is to call directly
> __vmalloc_node_range, which is not exported.
> 
> This means that a module can't vmalloc memory with small pages.
> 
> Case in point: KVM on s390x needs to vmalloc a large area, and it needs
> to be mapped with non-huge pages, because of a hardware limitation.
> 
> This patch adds the function vmalloc_no_huge, which works like vmalloc,
> but it is guaranteed to always back the mapping using small pages. This
> new function is exported, therefore it is usable by modules.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Acked-by: Nicholas Piggin <npiggin@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> ---
>   include/linux/vmalloc.h |  1 +
>   mm/vmalloc.c            | 16 ++++++++++++++++
>   2 files changed, 17 insertions(+)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 4d668abb6391..bfaaf0b6fa76 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
>   			const void *caller);
>   void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
>   		int node, const void *caller);
> +void *vmalloc_no_huge(unsigned long size);
>   
>   extern void vfree(const void *addr);
>   extern void vfree_atomic(const void *addr);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a13ac524f6ff..296a2fcc3fbe 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size)
>   }
>   EXPORT_SYMBOL(vmalloc);
>   
> +/**
> + * vmalloc_no_huge - allocate virtually contiguous memory using small pages
> + * @size:    allocation size
> + *
> + * Allocate enough non-huge pages to cover @size from the page level
> + * allocator and map them into contiguous kernel virtual space.
> + *
> + * Return: pointer to the allocated memory or %NULL on error
> + */
> +void *vmalloc_no_huge(unsigned long size)
> +{
> +	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
> +				    VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));
> +}
> +EXPORT_SYMBOL(vmalloc_no_huge);
> +
>   /**
>    * vzalloc - allocate virtually contiguous memory with zero fill
>    * @size:    allocation size
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb

Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge

[Uladzislau Rezki]

> On 14.06.21 15:23, Claudio Imbrenda wrote:
> > Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
> > support for hugepage vmalloc mappings, it also added the flag
> > VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to
> > be performed with 0-order non-huge pages.  This flag is not accessible
> > when calling vmalloc, the only option is to call directly
> > __vmalloc_node_range, which is not exported.
> > 
> > This means that a module can't vmalloc memory with small pages.
> > 
> > Case in point: KVM on s390x needs to vmalloc a large area, and it needs
> > to be mapped with non-huge pages, because of a hardware limitation.
> > 
> > This patch adds the function vmalloc_no_huge, which works like vmalloc,
> > but it is guaranteed to always back the mapping using small pages. This
> > new function is exported, therefore it is usable by modules.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > Acked-by: Nicholas Piggin <npiggin@gmail.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Nicholas Piggin <npiggin@gmail.com>
> > Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Christoph Hellwig <hch@infradead.org>
> > ---
> >   include/linux/vmalloc.h |  1 +
> >   mm/vmalloc.c            | 16 ++++++++++++++++
> >   2 files changed, 17 insertions(+)
> > 
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 4d668abb6391..bfaaf0b6fa76 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
> >   			const void *caller);
> >   void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
> >   		int node, const void *caller);
> > +void *vmalloc_no_huge(unsigned long size);
> >   extern void vfree(const void *addr);
> >   extern void vfree_atomic(const void *addr);
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index a13ac524f6ff..296a2fcc3fbe 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size)
> >   }
> >   EXPORT_SYMBOL(vmalloc);
> > +/**
> > + * vmalloc_no_huge - allocate virtually contiguous memory using small pages
> > + * @size:    allocation size
> > + *
> > + * Allocate enough non-huge pages to cover @size from the page level
> > + * allocator and map them into contiguous kernel virtual space.
> > + *
> > + * Return: pointer to the allocated memory or %NULL on error
> > + */
> > +void *vmalloc_no_huge(unsigned long size)
> > +{
> > +	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
> > +				    VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));
> > +}
> > +EXPORT_SYMBOL(vmalloc_no_huge);
> > +
> >   /**
> >    * vzalloc - allocate virtually contiguous memory with zero fill
> >    * @size:    allocation size
> > 
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
> 
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki

Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge

[Christoph Hellwig]

On Mon, Jun 14, 2021 at 03:23:56PM +0200, Claudio Imbrenda wrote:
> +void *vmalloc_no_huge(unsigned long size)
> +{
> +	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
> +				    VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));

Please avoid the overly long lines in favor of something actually
human-readable like:

	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
			GFP_KERNEL, PAGE_KERNEL, VM_NO_HUGE_VMAP,
			NUMA_NO_NODE, __builtin_return_address(0));

Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge

[David Rientjes]

On Mon, 14 Jun 2021, Claudio Imbrenda wrote:

> Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
> support for hugepage vmalloc mappings, it also added the flag
> VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to
> be performed with 0-order non-huge pages.  This flag is not accessible
> when calling vmalloc, the only option is to call directly
> __vmalloc_node_range, which is not exported.
> 
> This means that a module can't vmalloc memory with small pages.
> 
> Case in point: KVM on s390x needs to vmalloc a large area, and it needs
> to be mapped with non-huge pages, because of a hardware limitation.
> 
> This patch adds the function vmalloc_no_huge, which works like vmalloc,
> but it is guaranteed to always back the mapping using small pages. This
> new function is exported, therefore it is usable by modules.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Acked-by: Nicholas Piggin <npiggin@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Christoph Hellwig <hch@infradead.org>

Acked-by: David Rientjes <rientjes@google.com>

[PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

[Claudio Imbrenda]

The Create Secure Configuration Ultravisor Call does not support using
large pages for the virtual memory area. This is a hardware limitation.

This patch replaces the vzalloc call with an almost equivalent call to
the newly introduced vmalloc_no_huge function, which guarantees that
only small pages will be used for the backing.

The new call will not clear the allocated memory, but that has never
been an actual requirement.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
---
 arch/s390/kvm/pv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 813b6e93dc83..c8841f476e91 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -140,7 +140,12 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
 	/* Allocate variable storage */
 	vlen = ALIGN(virt * ((npages * PAGE_SIZE) / HPAGE_SIZE), PAGE_SIZE);
 	vlen += uv_info.guest_virt_base_stor_len;
-	kvm->arch.pv.stor_var = vzalloc(vlen);
+	/*
+	 * The Create Secure Configuration Ultravisor Call does not support
+	 * using large pages for the virtual memory area.
+	 * This is a hardware limitation.
+	 */
+	kvm->arch.pv.stor_var = vmalloc_no_huge(vlen);
 	if (!kvm->arch.pv.stor_var)
 		goto out_err;
 	return 0;
-- 
2.31.1

Re: [PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

[David Hildenbrand]

On 14.06.21 15:23, Claudio Imbrenda wrote:
> The Create Secure Configuration Ultravisor Call does not support using
> large pages for the virtual memory area. This is a hardware limitation.
> 
> This patch replaces the vzalloc call with an almost equivalent call to
> the newly introduced vmalloc_no_huge function, which guarantees that
> only small pages will be used for the backing.
> 
> The new call will not clear the allocated memory, but that has never
> been an actual requirement.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Acked-by: Nicholas Piggin <npiggin@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> ---
>   arch/s390/kvm/pv.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 813b6e93dc83..c8841f476e91 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -140,7 +140,12 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
>   	/* Allocate variable storage */
>   	vlen = ALIGN(virt * ((npages * PAGE_SIZE) / HPAGE_SIZE), PAGE_SIZE);
>   	vlen += uv_info.guest_virt_base_stor_len;
> -	kvm->arch.pv.stor_var = vzalloc(vlen);
> +	/*
> +	 * The Create Secure Configuration Ultravisor Call does not support
> +	 * using large pages for the virtual memory area.
> +	 * This is a hardware limitation.
> +	 */
> +	kvm->arch.pv.stor_var = vmalloc_no_huge(vlen);
>   	if (!kvm->arch.pv.stor_var)
>   		goto out_err;
>   	return 0;
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb

Re: [PATCH v4 0/2] mm: add vmalloc_no_huge and use it

[Andrew Morton]

On Mon, 14 Jun 2021 15:23:55 +0200 Claudio Imbrenda <imbrenda@linux.ibm.com> wrote:

> Add vmalloc_no_huge and export it, so modules can allocate memory with
> small pages.
> 
> Use the newly added vmalloc_no_huge in KVM on s390 to get around a
> hardware limitation.

Thanks.  I added

Fixes: 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") 

and also addressed the whitespace thing which Christoph noted.

No cc:stable since 121e6f3258fe3 wasn't in 5.12.