linux-kernel - Re: [PATCH v5 02/10] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)

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Message-ID: <20170815035138.qylh4mhpqom5g6qx@smitten>
Date:   Mon, 14 Aug 2017 21:51:38 -0600
From:   Tycho Andersen <tycho@...ker.com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com,
        Marco Benatto <marco.antonio.780@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Juerg Haefliger <juerg.haefliger@....com>
Subject: Re: [PATCH v5 02/10] mm, x86: Add support for eXclusive Page Frame
 Ownership (XPFO)

On Mon, Aug 14, 2017 at 09:47:18PM -0600, Tycho Andersen wrote:
> I'll do that for the next version

Actually looking closer, I think we just need to mirror the
debug_pagealloc_enabled() checks in set_kpte() from
split_large_page(),

diff --git a/arch/x86/mm/xpfo.c b/arch/x86/mm/xpfo.c
index a1344f27406c..c962bd7f34cc 100644
--- a/arch/x86/mm/xpfo.c
+++ b/arch/x86/mm/xpfo.c
@@ -54,9 +54,11 @@ inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot)
 
 		do_split = try_preserve_large_page(pte, (unsigned long)kaddr, &cpa);
 		if (do_split) {
-			spin_lock(&cpa_lock);
+			if (!debug_pagealloc_enabled())
+				spin_lock(&cpa_lock);
 			BUG_ON(split_large_page(&cpa, pte, (unsigned long)kaddr));
-			spin_unlock(&cpa_lock);
+			if (!debug_pagealloc_enabled())
+				spin_unlock(&cpa_lock);
 		}
 
 		break;


Tycho