2022-12-02 18:54:20

by Kristen Carlson Accardi

Subject: [PATCH v2 08/18] x86/sgx: Allow reclaiming up to 32 pages, but scan 16 by default

From: Sean Christopherson <[email protected]>

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 <[email protected]>
Signed-off-by: Kristen Carlson Accardi <[email protected]>
Cc: Sean Christopherson <[email protected]>
---
arch/x86/kernel/cpu/sgx/main.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 83aaf5cea7b9..f201ca85212f 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -18,6 +18,8 @@
#include "encl.h"
#include "encls.h"

+#define SGX_MAX_NR_TO_RECLAIM 32
+
struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
static int sgx_nr_epc_sections;
static struct task_struct *ksgxd_tsk;
@@ -273,7 +275,10 @@ 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
@@ -286,9 +291,9 @@ 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_MAX_NR_TO_RECLAIM];
struct sgx_epc_page *epc_page, *tmp;
struct sgx_encl_page *encl_page;
pgoff_t page_index;
@@ -297,7 +302,7 @@ static void __sgx_reclaim_pages(void)
int i;

spin_lock(&sgx_global_lru.lock);
- for (i = 0; i < SGX_NR_TO_SCAN; i++) {
+ for (i = 0; i < nr_to_scan; i++) {
epc_page = sgx_epc_peek_reclaimable(&sgx_global_lru);
if (!epc_page)
break;
@@ -327,7 +332,7 @@ static void __sgx_reclaim_pages(void)
list_for_each_entry_safe(epc_page, tmp, &iso, list) {
encl_page = epc_page->encl_owner;

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

page_index = PFN_DOWN(encl_page->desc - encl_page->encl->base);
@@ -371,9 +376,9 @@ static void __sgx_reclaim_pages(void)
}
}

-static void sgx_reclaim_pages(void)
+static void sgx_reclaim_pages(int nr_to_scan)
{
- __sgx_reclaim_pages();
+ __sgx_reclaim_pages(nr_to_scan);
cond_resched();
}

@@ -393,7 +398,7 @@ 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)
@@ -419,7 +424,7 @@ 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);
}

return 0;
@@ -598,7 +603,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
break;
}

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

if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
--
2.38.1

2022-12-08 10:09:42

by Jarkko Sakkinen

Subject: Re: [PATCH v2 08/18] x86/sgx: Allow reclaiming up to 32 pages, but scan 16 by default

On Thu, Dec 08, 2022 at 09:26:35AM +0000, Jarkko Sakkinen wrote:
> On Fri, Dec 02, 2022 at 10:36:44AM -0800, Kristen Carlson Accardi wrote:
> > From: Sean Christopherson <[email protected]>
> >
> > 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 <[email protected]>
> > Signed-off-by: Kristen Carlson Accardi <[email protected]>
> > Cc: Sean Christopherson <[email protected]>
> > ---
> > arch/x86/kernel/cpu/sgx/main.c | 25 +++++++++++++++----------
> > 1 file changed, 15 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> > index 83aaf5cea7b9..f201ca85212f 100644
> > --- a/arch/x86/kernel/cpu/sgx/main.c
> > +++ b/arch/x86/kernel/cpu/sgx/main.c
> > @@ -18,6 +18,8 @@
> > #include "encl.h"
> > #include "encls.h"
> >
> > +#define SGX_MAX_NR_TO_RECLAIM 32
>
> SGX_NR_TO_SCAN_MAX

Would also deserve a descriptive comment.

BR, Jarkko

2022-12-08 10:09:53

by Jarkko Sakkinen

Subject: Re: [PATCH v2 08/18] x86/sgx: Allow reclaiming up to 32 pages, but scan 16 by default

On Fri, Dec 02, 2022 at 10:36:44AM -0800, Kristen Carlson Accardi wrote:
> From: Sean Christopherson <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Kristen Carlson Accardi <[email protected]>
> Cc: Sean Christopherson <[email protected]>
> ---
> arch/x86/kernel/cpu/sgx/main.c | 25 +++++++++++++++----------
> 1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 83aaf5cea7b9..f201ca85212f 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -18,6 +18,8 @@
> #include "encl.h"
> #include "encls.h"
>
> +#define SGX_MAX_NR_TO_RECLAIM 32

SGX_NR_TO_SCAN_MAX

BR, Jarkko