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

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Message-ID: <bfaa49c58626932e65096b433c7f37a2c35ca382.camel@intel.com>
Date: Thu, 22 Jan 2026 11:42:39 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "tianwentong2000@...il.com" <tianwentong2000@...il.com>,
	"jarkko@...nel.org" <jarkko@...nel.org>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>
CC: "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 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;
		...
	};

?