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Subject[PATCH 4.9 037/119] arm64: KVM: Preserve RES1 bits in SCTLR_EL2
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Marc Zyngier <marc.zyngier@arm.com>

commit d68c1f7fd1b7148dab5fe658321d511998969f2d upstream.

__do_hyp_init has the rather bad habit of ignoring RES1 bits and
writing them back as zero. On a v8.0-8.2 CPU, this doesn't do anything
bad, but may end-up being pretty nasty on future revisions of the
architecture.

Let's preserve those bits so that we don't have to fix this later on.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/sysreg.h | 4 ++++
arch/arm64/kvm/hyp-init.S | 10 ++++++----
2 files changed, 10 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -94,6 +94,10 @@
#define SCTLR_ELx_A (1 << 1)
#define SCTLR_ELx_M 1

+#define SCTLR_EL2_RES1 ((1 << 4) | (1 << 5) | (1 << 11) | (1 << 16) | \
+ (1 << 16) | (1 << 18) | (1 << 22) | (1 << 23) | \
+ (1 << 28) | (1 << 29))
+
#define SCTLR_ELx_FLAGS (SCTLR_ELx_M | SCTLR_ELx_A | SCTLR_ELx_C | \
SCTLR_ELx_SA | SCTLR_ELx_I)

--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -102,10 +102,12 @@ __do_hyp_init:
tlbi alle2
dsb sy

- mrs x4, sctlr_el2
- and x4, x4, #SCTLR_ELx_EE // preserve endianness of EL2
- ldr x5, =SCTLR_ELx_FLAGS
- orr x4, x4, x5
+ /*
+ * Preserve all the RES1 bits while setting the default flags,
+ * as well as the EE bit on BE.
+ */
+ ldr x4, =(SCTLR_EL2_RES1 | SCTLR_ELx_FLAGS)
+CPU_BE( orr x4, x4, #SCTLR_ELx_EE)
msr sctlr_el2, x4
isb


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