linux-kernel - Re: [PATCH] x86/sgx: use vm_flags_t for vm_prot

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Message-ID: <CAGPELS5G42Esir0LHz6gAHKsO5gas48XiMtfOeQ+Kn62rDuicg@mail.gmail.com>
Date: Fri, 23 Jan 2026 14:15:49 +0800
From: TwT pupupu <tianwentong2000@...il.com>
To: "Huang, Kai" <kai.huang@...el.com>
Cc: "jarkko@...nel.org" <jarkko@...nel.org>, 
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, 
	"linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	"mingo@...hat.com" <mingo@...hat.com>, "tglx@...nel.org" <tglx@...nel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "bp@...en8.de" <bp@...en8.de>, 
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH] x86/sgx: use vm_flags_t for vm_prot_bits

On Wed, Jan 22, 2026 at 7:42 PM Huang, Kai <kai.huang@...el.com> wrote:
> Not sure we should change that too:
>
> struct sgx_encl_page {
> unsigned long desc;
> vm_flags_t vm_max_prot_bits:8;
> ...
> };
>
> ?
Hi, I'll include this in v2 for consistency. The :8
width is unchanged, so no functional or storage difference.

Huang, Kai <kai.huang@...el.com> 於 2026年1月22日週四 下午7:42寫道：
>
> On Thu, 2026-01-22 at 13:54 +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.
> >
> > No functional change intended.
> >
> > Signed-off-by: Wentong Tian <tianwentong2000@...il.com>
> > ---
> >  arch/x86/kernel/cpu/sgx/encl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > 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));
>
> Since commit d75fa3c94750 ("mm: update
> architecture and driver code to use vm_flags_t") already converted one
> 'vm_prot_bits' to vm_flags_t in sgx_encl_may_map(), this looks good to me
> too.
>
> One thing though:
>
> 'vm_prot_bits' is later bit-ANDed with entry->vm_max_prot_bits:
>
>         if ((entry->vm_max_prot_bits & vm_prot_bits) != vm_prot_bits)
>                 return ERR_PTR(-EFAULT);
>
> But 'vm_max_prot_bits' a 8-bit field of 'unsigned long' in 'struct
> sgx_encl_page':
>
>         struct sgx_encl_page {
>                 unsigned long desc;
>                 unsigned long vm_max_prot_bits:8;
>                 ...
>         };
>
> Not sure we should change that too:
>
>         struct sgx_encl_page {
>                 unsigned long desc;
>                 vm_flags_t vm_max_prot_bits:8;
>                 ...
>         };
>
> ?