On Sun, Nov 07, 2021 at 11:06:01AM -0800, Dave Hansen wrote:
On 11/7/21 10:06 AM, Jarkko Sakkinen wrote:
On Thu, Nov 04, 2021 at 03:38:55PM -0700, Dave Hansen wrote:
On 11/3/21 4:22 PM, Jarkko Sakkinen wrote:
--- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -22,6 +22,7 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, { unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK; struct sgx_encl *encl = encl_page->encl;
- struct inode *inode = file_inode(encl->backing); struct sgx_pageinfo pginfo; struct sgx_backing b; pgoff_t page_index;
@@ -60,6 +61,9 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, sgx_encl_put_backing(&b, false);
- /* Free the backing memory. */
- shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1);
- return ret;
}
This also misses tearing down the backing storage if it is in place at sgx_encl_release().
Hmm... sgx_encl_release() does fput(). Isn't that enough to tear it down, or does it require explicit truncate, i.e. something like
shmem_truncate_range(file_inode(encl->backing), encl->base, encl->size - 1);That's true, the page cache should all be torn down along with the fput(). *But*, it would be a very nice property if the backing storage was empty by this point. It essentially ensures that no enclave-runtime cases missed truncating the backing storage away.
What if an enclave is released a point when all of its pages are swapped out? Or even simpler case would an enclave that is larger than all of EPC.
What can be made sure is that for all pages, which are in EPC, the backing page is truncated.
Does a entry->epc_page==NULL page in there guarantee that it has backing storage?
Yes, it is an invariant. That what I was thinking to use for PCMD: iterate 32 pages and check if they have a faulted page.
I think the rule should be that entry->epc_page==NULL enclave pages have backing storage. All entry->epc_page!=NULL do *not* have backing storage.
Yes, that is the goal of this patch.
/Jarkko