[PATCH v3 10/28] x86/sgx: Allow reclaiming up to 32 pages, but scan 16 by default

Haitao Huang
2023-07-12T23:02:47Z

From: Sean Christopherson <sean.j.christopherson@intel.com>

Modify sgx_reclaim_pages() to take a parameter that specifies the
number of pages to scan for reclaiming. Specify a max value of
32, but scan 16 in the usual case. This allows the number of pages
sgx_reclaim_pages() scans to be specified by the caller, and adjusted
in future patches.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>
---
arch/x86/kernel/cpu/sgx/main.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index f3a3ed894616..cd5e5517866a 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -17,6 +17,10 @@
#include "driver.h"
#include "encl.h"
#include "encls.h"
+/**
+ * Maximum number of pages to scan for reclaiming.
+ */
+#define SGX_NR_TO_SCAN_MAX 32

struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
static int sgx_nr_epc_sections;
@@ -279,7 +283,10 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
mutex_unlock(&encl->lock);
}

-/*
+/**
+ * sgx_reclaim_pages() - Reclaim EPC pages from the consumers
+ * @nr_to_scan: Number of EPC pages to scan for reclaim
+ *
* Take a fixed number of pages from the head of the active page pool and
* reclaim them to the enclave's private shmem files. Skip the pages, which have
* been accessed since the last scan. Move those pages to the tail of active
@@ -292,9 +299,9 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
* problematic as it would increase the lock contention too much, which would
* halt forward progress.
*/
-static void sgx_reclaim_pages(void)
+static void sgx_reclaim_pages(int nr_to_scan)
{
- struct sgx_backing backing[SGX_NR_TO_SCAN];
+ struct sgx_backing backing[SGX_NR_TO_SCAN_MAX];
struct sgx_epc_page *epc_page, *tmp;
struct sgx_encl_page *encl_page;
pgoff_t page_index;
@@ -332,7 +339,7 @@ static void sgx_reclaim_pages(void)
list_for_each_entry_safe(epc_page, tmp, &iso, list) {
encl_page = epc_page->encl_page;

- if (!sgx_reclaimer_age(epc_page))
+ if (i == SGX_NR_TO_SCAN_MAX || !sgx_reclaimer_age(epc_page))
goto skip;

page_index = PFN_DOWN(encl_page->desc - encl_page->encl->base);
@@ -387,7 +394,7 @@ static bool sgx_should_reclaim(unsigned long watermark)
void sgx_reclaim_direct(void)
{
if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
- sgx_reclaim_pages();
+ sgx_reclaim_pages(SGX_NR_TO_SCAN);
}

static int ksgxd(void *p)
@@ -410,7 +417,7 @@ static int ksgxd(void *p)
sgx_should_reclaim(SGX_NR_HIGH_PAGES));

if (sgx_should_reclaim(SGX_NR_HIGH_PAGES))
- sgx_reclaim_pages();
+ sgx_reclaim_pages(SGX_NR_TO_SCAN);

cond_resched();
}
@@ -582,7 +589,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
break;
}

- sgx_reclaim_pages();
+ sgx_reclaim_pages(SGX_NR_TO_SCAN);
cond_resched();
}

--
2.25.1