[v2] x86/sgx: use vm_flags_t for vm_prot_bits

[PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

Posted by Wentong Tian 2 weeks, 1 day ago

The vm_flags_t type is the dedicated type for virtual memory flags.
Architecture and driver code should use this type instead of assuming
vm_flags is an unsigned long, as the underlying type may change in the
future.

This follows the cleanup in commit d75fa3c94750 ("mm: update
architecture and driver code to use vm_flags_t") by converting the
remaining vm_prot_bits usage in SGX code. Also, update the vm_max_prot_bits
type in struct sgx_encl_page to vm_flags_t for consistency.

No functional change intended.

Signed-off-by: Wentong Tian <tianwentong2000@gmail.com>
---
v2:
 - Also convert the type of vm_max_prot_bits in struct sgx_encl_page
   to vm_flags_t, as suggested.

 arch/x86/kernel/cpu/sgx/encl.c | 2 +-
 arch/x86/kernel/cpu/sgx/encl.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index cf149b9f4916..814edcde225d 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -281,7 +281,7 @@ static struct sgx_encl_page *sgx_encl_load_page_in_vma(struct sgx_encl *encl,
 						       unsigned long addr,
 						       vm_flags_t vm_flags)
 {
-	unsigned long vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
+	vm_flags_t vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
 	struct sgx_encl_page *entry;
 
 	entry = xa_load(&encl->page_array, PFN_DOWN(addr));
diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
index 8ff47f6652b9..0e0b97e91905 100644
--- a/arch/x86/kernel/cpu/sgx/encl.h
+++ b/arch/x86/kernel/cpu/sgx/encl.h
@@ -27,7 +27,7 @@
 
 struct sgx_encl_page {
 	unsigned long desc;
-	unsigned long vm_max_prot_bits:8;
+	vm_flags_t vm_max_prot_bits:8;
 	enum sgx_page_type type:16;
 	struct sgx_epc_page *epc_page;
 	struct sgx_encl *encl;
-- 
2.34.1

Re: [PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

Posted by Jarkko Sakkinen 1 week, 5 days ago

On Thu, Jan 22, 2026 at 09:36:33PM +0800, Wentong Tian wrote:
> The vm_flags_t type is the dedicated type for virtual memory flags.
> Architecture and driver code should use this type instead of assuming
> vm_flags is an unsigned long, as the underlying type may change in the
> future.
> 
> This follows the cleanup in commit d75fa3c94750 ("mm: update
> architecture and driver code to use vm_flags_t") by converting the
> remaining vm_prot_bits usage in SGX code. Also, update the vm_max_prot_bits
> type in struct sgx_encl_page to vm_flags_t for consistency.
> 
> No functional change intended.
> 
> Signed-off-by: Wentong Tian <tianwentong2000@gmail.com>
> ---
> v2:
>  - Also convert the type of vm_max_prot_bits in struct sgx_encl_page
>    to vm_flags_t, as suggested.
> 
>  arch/x86/kernel/cpu/sgx/encl.c | 2 +-
>  arch/x86/kernel/cpu/sgx/encl.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index cf149b9f4916..814edcde225d 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -281,7 +281,7 @@ static struct sgx_encl_page *sgx_encl_load_page_in_vma(struct sgx_encl *encl,
>  						       unsigned long addr,
>  						       vm_flags_t vm_flags)
>  {
> -	unsigned long vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
> +	vm_flags_t vm_prot_bits = vm_flags & VM_ACCESS_FLAGS;
>  	struct sgx_encl_page *entry;
>  
>  	entry = xa_load(&encl->page_array, PFN_DOWN(addr));
> diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
> index 8ff47f6652b9..0e0b97e91905 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.h
> +++ b/arch/x86/kernel/cpu/sgx/encl.h
> @@ -27,7 +27,7 @@
>  
>  struct sgx_encl_page {
>  	unsigned long desc;
> -	unsigned long vm_max_prot_bits:8;
> +	vm_flags_t vm_max_prot_bits:8;
>  	enum sgx_page_type type:16;
>  	struct sgx_epc_page *epc_page;
>  	struct sgx_encl *encl;

OK, I missed the remark from Kai, but it is acceptable.

> -- 
> 2.34.1
> 

So again:

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko

Re: [PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

Posted by Huang, Kai 2 weeks, 1 day ago

On Thu, 2026-01-22 at 21:36 +0800, Wentong Tian wrote:
> The vm_flags_t type is the dedicated type for virtual memory flags.
> Architecture and driver code should use this type instead of assuming
> vm_flags is an unsigned long, as the underlying type may change in the
> future.
> 
> This follows the cleanup in commit d75fa3c94750 ("mm: update
> architecture and driver code to use vm_flags_t") by converting the
> remaining vm_prot_bits usage in SGX code. Also, update the vm_max_prot_bits
> type in struct sgx_encl_page to vm_flags_t for consistency.
> 
> No functional change intended.
> 
> Signed-off-by: Wentong Tian <tianwentong2000@gmail.com>
> ---
> v2:
>  - Also convert the type of vm_max_prot_bits in struct sgx_encl_page
>    to vm_flags_t, as suggested.

Hmm I was actually just pointing out, but not suggesting, since I am not
sure (honestly).

Back to technical:

Gcc doc says:

  A structure field declaration with an integer type can specify the 
  number of bits the field should occupy. We call that a bit field.

With vm_flags_t I think "theoretically" it could stop being integer type
someday.  But I guess the advantage is when someone does that that can
trigger build error here (so that we can be aware) which perhaps isn't a
bad thing?

Re: [PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

Posted by TwT pupupu 2 weeks, 1 day ago

Sorry about that, I'll make sure to reply to the list.
On Thu, Jan 23, 2026 at 4:57 AM Huang, Kai <kai.huang@intel.com> wrote:
> Hmm I was actually just pointing out, but not suggesting, since I am not
> sure (honestly).
Sorry for the misunderstanding.
> With vm_flags_t I think "theoretically" it could stop being integer type
> someday. But I guess the advantage is when someone does that that can
> trigger build error here (so that we can be aware) which perhaps isn't a
> bad thing?
You're right, the build error would be a useful early warning if
vm_flags_t ever becomes incompatible. I'm fine either way, let me know
if you'd prefer keeping
unsigned long and I'll send a v3.

Re: [PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

Posted by Huang, Kai 2 weeks, 1 day ago

> > With vm_flags_t I think "theoretically" it could stop being integer type
> > someday. But I guess the advantage is when someone does that that can
> > trigger build error here (so that we can be aware) which perhaps isn't a
> > bad thing?
> You're right, the build error would be a useful early warning if
> vm_flags_t ever becomes incompatible. 
> 

Agreed.  It's what type safety means IMHO.


> I'm fine either way, let me know
> if you'd prefer keeping
> unsigned long and I'll send a v3.

It's up to maintainer(s), but v2 makes sense to me, so:

Acked-by: Kai Huang <kai.huang@intel.com>