On Mon, Apr 04, 2022 at 09:49:16AM -0700, Reinette Chatre wrote: > The SGX reclaimer removes page table entries pointing to pages that are > moved to swap. > > SGX2 enables changes to pages belonging to an initialized enclave, thus > enclave pages may have their permission or type changed while the page > is being accessed by an enclave. Supporting SGX2 requires page table > entries to be removed so that any cached mappings to changed pages > are removed. For example, with the ability to change enclave page types > a regular enclave page may be changed to a Thread Control Structure > (TCS) page that may not be accessed by an enclave. > > Factor out the code removing page table entries to a separate function > sgx_zap_enclave_ptes(), fixing accuracy of comments in the process, > and make it available to the upcoming SGX2 code. > > Place sgx_zap_enclave_ptes() with the rest of the enclave code in > encl.c interacting with the page table since this code is no longer > unique to the reclaimer. > > Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> > --- > No changes since V2 > > Changes since V1: > - Elaborate why SGX2 needs this ability (Jarkko). > - More specific subject. > - Fix kernel-doc to have brackets in function name. > > arch/x86/kernel/cpu/sgx/encl.c | 45 +++++++++++++++++++++++++++++++++- > arch/x86/kernel/cpu/sgx/encl.h | 2 +- > arch/x86/kernel/cpu/sgx/main.c | 31 ++--------------------- > 3 files changed, 47 insertions(+), 31 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c > index 8de9bebc4d81..c77a62432862 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -605,7 +605,7 @@ int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm) > > spin_lock(&encl->mm_lock); > list_add_rcu(&encl_mm->list, &encl->mm_list); > - /* Pairs with smp_rmb() in sgx_reclaimer_block(). */ > + /* Pairs with smp_rmb() in sgx_zap_enclave_ptes(). */ > smp_wmb(); > encl->mm_list_version++; > spin_unlock(&encl->mm_lock); > @@ -792,6 +792,49 @@ int sgx_encl_test_and_clear_young(struct mm_struct *mm, > return ret; > } > > +/** > + * sgx_zap_enclave_ptes() - remove PTEs mapping the address from enclave > + * @encl: the enclave > + * @addr: page aligned pointer to single page for which PTEs will be removed > + * > + * Multiple VMAs may have an enclave page mapped. Remove the PTE mapping > + * @addr from each VMA. Ensure that page fault handler is ready to handle > + * new mappings of @addr before calling this function. > + */ > +void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr) > +{ > + unsigned long mm_list_version; > + struct sgx_encl_mm *encl_mm; > + struct vm_area_struct *vma; > + int idx, ret; > + > + do { > + mm_list_version = encl->mm_list_version; > + > + /* Pairs with smp_wmb() in sgx_encl_mm_add(). */ > + smp_rmb(); > + > + idx = srcu_read_lock(&encl->srcu); > + > + list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) { > + if (!mmget_not_zero(encl_mm->mm)) > + continue; > + > + mmap_read_lock(encl_mm->mm); > + > + ret = sgx_encl_find(encl_mm->mm, addr, &vma); > + if (!ret && encl == vma->vm_private_data) > + zap_vma_ptes(vma, addr, PAGE_SIZE); > + > + mmap_read_unlock(encl_mm->mm); > + > + mmput_async(encl_mm->mm); > + } > + > + srcu_read_unlock(&encl->srcu, idx); > + } while (unlikely(encl->mm_list_version != mm_list_version)); > +} > + > /** > * sgx_alloc_va_page() - Allocate a Version Array (VA) page > * > diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h > index e59c2cbf71e2..1b15d22f6757 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.h > +++ b/arch/x86/kernel/cpu/sgx/encl.h > @@ -111,7 +111,7 @@ int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, > void sgx_encl_put_backing(struct sgx_backing *backing, bool do_write); > int sgx_encl_test_and_clear_young(struct mm_struct *mm, > struct sgx_encl_page *page); > - > +void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr); > struct sgx_epc_page *sgx_alloc_va_page(void); > unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page); > void sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset); > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index fa33922879bf..ce9e87d5f8ec 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -137,36 +137,9 @@ static void sgx_reclaimer_block(struct sgx_epc_page *epc_page) > struct sgx_encl_page *page = epc_page->owner; > unsigned long addr = page->desc & PAGE_MASK; > struct sgx_encl *encl = page->encl; > - unsigned long mm_list_version; > - struct sgx_encl_mm *encl_mm; > - struct vm_area_struct *vma; > - int idx, ret; > - > - do { > - mm_list_version = encl->mm_list_version; > - > - /* Pairs with smp_rmb() in sgx_encl_mm_add(). */ > - smp_rmb(); > - > - idx = srcu_read_lock(&encl->srcu); > - > - list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) { > - if (!mmget_not_zero(encl_mm->mm)) > - continue; > - > - mmap_read_lock(encl_mm->mm); > - > - ret = sgx_encl_find(encl_mm->mm, addr, &vma); > - if (!ret && encl == vma->vm_private_data) > - zap_vma_ptes(vma, addr, PAGE_SIZE); > - > - mmap_read_unlock(encl_mm->mm); > - > - mmput_async(encl_mm->mm); > - } > + int ret; > > - srcu_read_unlock(&encl->srcu, idx); > - } while (unlikely(encl->mm_list_version != mm_list_version)); > + sgx_zap_enclave_ptes(encl, addr); > > mutex_lock(&encl->lock); > > -- > 2.25.1 > Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko