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Message-ID: <YuJBjq/4dALm//rf@kernel.org>
Date: Thu, 28 Jul 2022 10:58:06 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Kristen Carlson Accardi <kristen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org,
Dave Hansen <dave.hansen@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
linux-sgx@...r.kernel.org
Subject: Re: [PATCH] x86/sgx: Improve comments for
sgx_encl_lookup/alloc_backing()
On Wed, Jul 20, 2022 at 11:21:19AM -0700, Kristen Carlson Accardi wrote:
> Modify the comments for sgx_encl_lookup_backing() and for
> sgx_encl_alloc_backing() to indicate that they take a reference
> which must be dropped with a call to sgx_encl_put_backing().
> Make sgx_encl_lookup_backing() static for now, and change the
> name of sgx_encl_get_backing() to __sgx_encl_get_backing() to
> make it more clear that sgx_encl_get_backing() is an internal
> function.
>
> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
The rename is unnecessary.
> ---
> arch/x86/kernel/cpu/sgx/encl.c | 21 ++++++++++++++-------
> arch/x86/kernel/cpu/sgx/encl.h | 2 --
> 2 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index 19876ebfb504..325c2d59e6b4 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -12,6 +12,9 @@
> #include "encls.h"
> #include "sgx.h"
>
> +static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
> + struct sgx_backing *backing);
> +
> #define PCMDS_PER_PAGE (PAGE_SIZE / sizeof(struct sgx_pcmd))
> /*
> * 32 PCMD entries share a PCMD page. PCMD_FIRST_MASK is used to
> @@ -706,7 +709,7 @@ static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
> }
>
> /**
> - * sgx_encl_get_backing() - Pin the backing storage
> + * __sgx_encl_get_backing() - Pin the backing storage
> * @encl: an enclave pointer
> * @page_index: enclave page index
> * @backing: data for accessing backing storage for the page
> @@ -718,7 +721,7 @@ static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
> * 0 on success,
> * -errno otherwise.
> */
> -static int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
> +static int __sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
> struct sgx_backing *backing)
> {
> pgoff_t page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);
> @@ -794,7 +797,7 @@ static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
> }
>
> /**
> - * sgx_encl_alloc_backing() - allocate a new backing storage page
> + * sgx_encl_alloc_backing() - create a new backing storage page
> * @encl: an enclave pointer
> * @page_index: enclave page index
> * @backing: data for accessing backing storage for the page
> @@ -802,7 +805,9 @@ static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
> * When called from ksgxd, sets the active memcg from one of the
> * mms in the enclave's mm_list prior to any backing page allocation,
> * in order to ensure that shmem page allocations are charged to the
> - * enclave.
> + * enclave. Create a backing page for loading data back into an EPC page with
> + * ELDU. This function takes a reference on a new backing page which
> + * must be dropped with a corresponding call to sgx_encl_put_backing().
> *
> * Return:
> * 0 on success,
> @@ -815,7 +820,7 @@ int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
> struct mem_cgroup *memcg = set_active_memcg(encl_memcg);
> int ret;
>
> - ret = sgx_encl_get_backing(encl, page_index, backing);
> + ret = __sgx_encl_get_backing(encl, page_index, backing);
>
> set_active_memcg(memcg);
> mem_cgroup_put(encl_memcg);
> @@ -833,15 +838,17 @@ int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
> * It is the caller's responsibility to ensure that it is appropriate to use
> * sgx_encl_lookup_backing() rather than sgx_encl_alloc_backing(). If lookup is
> * not used correctly, this will cause an allocation which is not accounted for.
> + * This function takes a reference on an existing backing page which must be
> + * dropped with a corresponding call to sgx_encl_put_backing().
> *
> * Return:
> * 0 on success,
> * -errno otherwise.
> */
> -int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
> +static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
> struct sgx_backing *backing)
> {
> - return sgx_encl_get_backing(encl, page_index, backing);
> + return __sgx_encl_get_backing(encl, page_index, backing);
> }
>
> /**
> diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
> index 332ef3568267..d731ef53f815 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.h
> +++ b/arch/x86/kernel/cpu/sgx/encl.h
> @@ -106,8 +106,6 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
> bool current_is_ksgxd(void);
> void sgx_encl_release(struct kref *ref);
> int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm);
> -int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index,
> - struct sgx_backing *backing);
> int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index,
> struct sgx_backing *backing);
> void sgx_encl_put_backing(struct sgx_backing *backing);
> --
> 2.36.1
>
BR, JArkko
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