linux-kernel - [PATCH 10/11] Handle async PF in non preemptable context.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun,  1 Nov 2009 13:56:29 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 10/11] Handle async PF in non preemptable context.

If async page fault is received by idle task or when preemp_count is
not zero guest cannot reschedule, so make "wait for page" hypercall
and comtinue only after a page is ready.

Signed-off-by: Gleb Natapov <gleb@...hat.com>
---
 arch/x86/kernel/kvm.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 79d291f..1bd8b8d 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -162,10 +162,24 @@ int kvm_handle_pf(struct pt_regs *regs, unsigned long error_code)
 	switch (reason) {
 	default:
 		return 0;
-	case KVM_PV_REASON_PAGE_NP:
+	case KVM_PV_REASON_PAGE_NP: {
+		int cpu, idle;
+		cpu = get_cpu();
+		idle = idle_cpu(cpu);
+		put_cpu();
+
+		/*
+		 * We cannot reschedule. Wait for page to be ready.
+		 */
+		if (idle || preempt_count()) {
+			kvm_hypercall0(KVM_HC_WAIT_FOR_ASYNC_PF);
+			break;
+		}
+
 		/* real page is missing. */
 		apf_task_wait(current, token);
 		break;
+	}
 	case KVM_PV_REASON_PAGE_READY:
 		apf_task_wake(token);
 		break;
-- 
1.6.3.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/