linux-kernel - [PATCH 3/3] x86/paravirt: Use pte_val instead of pte_flags on CPA pageattr

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Date:	Tue,  8 Nov 2011 16:15:14 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org, len.brown@...el.com,
	tglx@...utronix.de, jeremy@...p.org, hpa@...or.com, bp@...en8.de,
	tj@...nel.org, trenn@...e.de
Cc:	mingo@...hat.com, xen-devel@...ts.xensource.com,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	stable@...nel.org
Subject: [PATCH 3/3] x86/paravirt: Use pte_val instead of pte_flags on CPA pageattr_test

For details refer to patch "x86/paravirt: Use pte_attrs instead of
pte_flags on CPA/set_p.._wb/wc operations." which explains that
some pages have the _PAGE_PWT bit set in the _PAGE_PSE field
when running under Xen.

When pageattr_test is running it uses pte_flags to check whether
it succedded in setting _PAGE_UNUSED1 bit, but also whether the
page had _PAGE_PSE. This can happen when one of the randomly selected
pages to be tested is a page that has been set to be _PAGE_WC
as under Xen, that field is under _PAGE_PSE. Since the 'pte_huge'
call is using the pte_flags(x) macro, which extracts the "raw" contents
of the PTE, the translation of _PAGE_PSE -> _PAGE_PWT does not happen
and we incorrectly identify the PTE as bad.

Using the 'pte_val' instead of 'pte_flags' fixes the problem and
this patch does that.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC: stable@...nel.org
---
 arch/x86/mm/pageattr-test.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/pageattr-test.c b/arch/x86/mm/pageattr-test.c
index b008656..da853e3 100644
--- a/arch/x86/mm/pageattr-test.c
+++ b/arch/x86/mm/pageattr-test.c
@@ -38,6 +38,10 @@ static int pte_testbit(pte_t pte)
 {
 	return pte_flags(pte) & _PAGE_UNUSED1;
 }
+static int pte_testhuge(pte_t pte)
+{
+	return pte_val(pte) & _PAGE_PSE;
+}

 struct split_state {
 	long lpg, gpg, spg, exec;
@@ -180,7 +184,7 @@ static int pageattr_test(void)
 		}

 		pte = lookup_address(addr[i], &level);
-		if (!pte || !pte_testbit(*pte) || pte_huge(*pte)) {
+		if (!pte || !pte_testbit(*pte) || pte_testhuge(*pte)) {
 			printk(KERN_ERR "CPA %lx: bad pte %Lx\n", addr[i],
 				pte ? (u64)pte_val(*pte) : 0ULL);
 			failed++;
-- 
1.7.7.1

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