iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

x86/sgx: Free up EPC pages directly to support large page ranges

Browse Source 
The page reclaimer ensures availability of EPC pages across all
enclaves. In support of this it runs independently from the
individual enclaves in order to take locks from the different
enclaves as it writes pages to swap.

When needing to load a page from swap an EPC page needs to be
available for its contents to be loaded into. Loading an existing
enclave page from swap does not reclaim EPC pages directly if
none are available, instead the reclaimer is woken when the
available EPC pages are found to be below a watermark.

When iterating over a large number of pages in an oversubscribed
environment there is a race between the reclaimer woken up and
EPC pages reclaimed fast enough for the page operations to proceed.

Ensure there are EPC pages available before attempting to load
a page that may potentially be pulled from swap into an available
EPC page.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/a0d8f037c4a075d56bf79f432438412985f7ff7a.1652137848.git.reinette.chatre@intel.com
This commit is contained in:
Reinette Chatre 2022-05-10 11:08:56 -07:00 committed by Dave Hansen
parent 9849bb2715
commit a0506b3b06
3 changed files with 18 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/kernel/cpu/sgx/ioctl.c
View File

@ -745,6 +745,8 @@ sgx_enclave_restrict_permissions(struct sgx_encl *encl,
for (c = 0 ; c < modp->length; c += PAGE_SIZE) {
addr = encl->base + modp->offset + c;
sgx_reclaim_direct();
mutex_lock(&encl->lock);
entry = sgx_encl_load_page(encl, addr);
@ -910,6 +912,8 @@ static long sgx_enclave_modify_types(struct sgx_encl *encl,
for (c = 0 ; c < modt->length; c += PAGE_SIZE) {
addr = encl->base + modt->offset + c;
sgx_reclaim_direct();
mutex_lock(&encl->lock);
entry = sgx_encl_load_page(encl, addr);
@ -1096,6 +1100,8 @@ static long sgx_encl_remove_pages(struct sgx_encl *encl,
for (c = 0 ; c < params->length; c += PAGE_SIZE) {
addr = encl->base + params->offset + c;
sgx_reclaim_direct();
mutex_lock(&encl->lock);
entry = sgx_encl_load_page(encl, addr);

11
arch/x86/kernel/cpu/sgx/main.c
View File

@ -375,6 +375,17 @@ static bool sgx_should_reclaim(unsigned long watermark)
!list_empty(&sgx_active_page_list);
}
/*
* sgx_reclaim_direct() should be called (without enclave's mutex held)
* in locations where SGX memory resources might be low and might be
* needed in order to make forward progress.
*/
void sgx_reclaim_direct(void)
{
if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
sgx_reclaim_pages();
}
static int ksgxd(void *p)
{
set_freezable();

1
arch/x86/kernel/cpu/sgx/sgx.h
View File

@ -86,6 +86,7 @@ static inline void *sgx_get_epc_virt_addr(struct sgx_epc_page *page)
struct sgx_epc_page *__sgx_alloc_epc_page(void);
void sgx_free_epc_page(struct sgx_epc_page *page);
void sgx_reclaim_direct(void);
void sgx_mark_page_reclaimable(struct sgx_epc_page *page);
int sgx_unmark_page_reclaimable(struct sgx_epc_page *page);
struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim);