linux-kernel - [PATCH 4.9 038/125] powerpc/pseries: Fix passing of pp0 in updatepp() and updateboltedpp()

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Message-Id: <20170725192016.445582189@linuxfoundation.org>
Date:   Tue, 25 Jul 2017 12:19:13 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Balbir Singh <bsingharora@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.9 038/125] powerpc/pseries: Fix passing of pp0 in updatepp() and updateboltedpp()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Balbir Singh <bsingharora@...il.com>

commit e71ff982ae4c17d176e9f0132157d54973788377 upstream.

Once upon a time there were only two PP (page protection) bits. In ISA
2.03 an additional PP bit was added, but because of the layout of the
HPTE it could not be made contiguous with the existing PP bits.

The result is that we now have three PP bits, named pp0, pp1, pp2,
where pp0 occupies bit 63 of dword 1 of the HPTE and pp1 and pp2
occupy bits 1 and 0 respectively. Until recently Linux hasn't used
pp0, however with the addition of _PAGE_KERNEL_RO we started using it.

The problem arises in the LPAR code, where we need to translate the PP
bits into the argument for the H_PROTECT hypercall. Currently the code
only passes bits 0-2 of newpp, which covers pp1, pp2 and N (no
execute), meaning pp0 is not passed to the hypervisor at all.

We can't simply pass it through in bit 63, as that would collide with a
different field in the flags argument, as defined in PAPR. Instead we
have to shift it down to bit 8 (IBM bit 55).

Fixes: e58e87adc8bf ("powerpc/mm: Update _PAGE_KERNEL_RO")
Signed-off-by: Balbir Singh <bsingharora@...il.com>
[mpe: Simplify the test, rework change log]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/platforms/pseries/lpar.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -279,7 +279,7 @@ static long pSeries_lpar_hpte_updatepp(u
 				       int ssize, unsigned long inv_flags)
 {
 	unsigned long lpar_rc;
-	unsigned long flags = (newpp & 7) | H_AVPN;
+	unsigned long flags;
 	unsigned long want_v;

 	want_v = hpte_encode_avpn(vpn, psize, ssize);
@@ -287,6 +287,11 @@ static long pSeries_lpar_hpte_updatepp(u
 	pr_devel("    update: avpnv=%016lx, hash=%016lx, f=%lx, psize: %d ...",
 		 want_v, slot, flags, psize);

+	flags = (newpp & 7) | H_AVPN;
+	if (mmu_has_feature(MMU_FTR_KERNEL_RO))
+		/* Move pp0 into bit 8 (IBM 55) */
+		flags |= (newpp & HPTE_R_PP0) >> 55;
+
 	lpar_rc = plpar_pte_protect(flags, slot, want_v);

 	if (lpar_rc == H_NOT_FOUND) {
@@ -358,6 +363,10 @@ static void pSeries_lpar_hpte_updatebolt
 	BUG_ON(slot == -1);

 	flags = newpp & 7;
+	if (mmu_has_feature(MMU_FTR_KERNEL_RO))
+		/* Move pp0 into bit 8 (IBM 55) */
+		flags |= (newpp & HPTE_R_PP0) >> 55;
+
 	lpar_rc = plpar_pte_protect(flags, slot, 0);

 	BUG_ON(lpar_rc != H_SUCCESS);