Re: [PATCH v36 09/24] x86/sgx: Add __sgx_alloc_epc_page() and sgx_free_epc_page()

Thu, 06 Aug 2020 09:57:21 -0700 

On Thursday, 2020-07-16 at 16:52:48 +03, Jarkko Sakkinen wrote:
> Add __sgx_alloc_epc_page(), which iterates through EPC sections and borrows
> a page structure that is not used by anyone else. When a page is no longer
> needed it must be released with sgx_free_epc_page(). This function
> implicitly calls ENCLS[EREMOVE], which will return the page to the
> uninitialized state (i.e. not required from caller part).
>
> Acked-by: Jethro Beekman <[email protected]>
> Co-developed-by: Sean Christopherson <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Jarkko Sakkinen <[email protected]>

Reviewed-by: Darren Kenny <[email protected]>

> ---
>  arch/x86/kernel/cpu/sgx/main.c | 62 ++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/cpu/sgx/sgx.h  |  3 ++
>  2 files changed, 65 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index c5831e3db14a..97c6895fb6c9 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -83,6 +83,68 @@ static bool __init sgx_page_reclaimer_init(void)
>       return true;
>  }
>  
> +static struct sgx_epc_page *__sgx_alloc_epc_page_from_section(struct 
> sgx_epc_section *section)
> +{
> +     struct sgx_epc_page *page;
> +
> +     if (list_empty(&section->page_list))
> +             return NULL;
> +
> +     page = list_first_entry(&section->page_list, struct sgx_epc_page, list);
> +     list_del_init(&page->list);
> +
> +     return page;
> +}
> +
> +/**
> + * __sgx_alloc_epc_page() - Allocate an EPC page
> + *
> + * Iterate through EPC sections and borrow a free EPC page to the caller. 
> When a
> + * page is no longer needed it must be released with sgx_free_epc_page().
> + *
> + * Return:
> + *   an EPC page,
> + *   -errno on error
> + */
> +struct sgx_epc_page *__sgx_alloc_epc_page(void)
> +{
> +     struct sgx_epc_section *section;
> +     struct sgx_epc_page *page;
> +     int i;
> +
> +     for (i = 0; i < sgx_nr_epc_sections; i++) {
> +             section = &sgx_epc_sections[i];
> +             spin_lock(&section->lock);
> +             page = __sgx_alloc_epc_page_from_section(section);
> +             spin_unlock(&section->lock);
> +
> +             if (page)
> +                     return page;
> +     }
> +
> +     return ERR_PTR(-ENOMEM);
> +}
> +
> +/**
> + * sgx_free_epc_page() - Free an EPC page
> + * @page:    an EPC page
> + *
> + * Call EREMOVE for an EPC page and insert it back to the list of free pages.
> + */
> +void sgx_free_epc_page(struct sgx_epc_page *page)
> +{
> +     struct sgx_epc_section *section = sgx_get_epc_section(page);
> +     int ret;
> +
> +     ret = __eremove(sgx_get_epc_addr(page));
> +     if (WARN_ONCE(ret, "EREMOVE returned %d (0x%x)", ret, ret))
> +             return;
> +
> +     spin_lock(&section->lock);
> +     list_add_tail(&page->list, &section->page_list);
> +     spin_unlock(&section->lock);
> +}
> +
>  static void __init sgx_free_epc_section(struct sgx_epc_section *section)
>  {
>       struct sgx_epc_page *page;
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index dff4f5f16d09..fce756c3434b 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -49,4 +49,7 @@ static inline void *sgx_get_epc_addr(struct sgx_epc_page 
> *page)
>       return section->va + (page->desc & PAGE_MASK) - section->pa;
>  }
>  
> +struct sgx_epc_page *__sgx_alloc_epc_page(void);
> +void sgx_free_epc_page(struct sgx_epc_page *page);
> +
>  #endif /* _X86_SGX_H */
> -- 
> 2.25.1

Reply via email to