ARM: KVM: perform save/restore of PAR
commit 6a077e4ab9cbfbf279fb955bae05b03781c97013 upstream.
Not saving PAR is an unfortunate oversight. If the guest performs
an AT* operation and gets scheduled out before reading the result
of the translation from PAR, it could become corrupted by another
guest or the host.
Saving this register is made slightly more complicated as KVM also
uses it on the permission fault handling path, leading to an ugly
"stash and restore" sequence. Fortunately, this is already a slow
path so we don't really care. Also, Linux doesn't do any AT*
operation, so Linux guests are not impacted by this bug.
[ Slightly tweaked to use an even register as first operand to ldrd
and strd operations in interrupts_head.S - Christoffer ]
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Jonghwan Choi <jhbird.choi@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index f7793df..d0a8fa3 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -414,6 +414,10 @@
mrcne p15, 4, r2, c6, c0, 4 @ HPFAR
bne 3f
+ /* Preserve PAR */
+ mrrc p15, 0, r0, r1, c7 @ PAR
+ push {r0, r1}
+
/* Resolve IPA using the xFAR */
mcr p15, 0, r2, c7, c8, 0 @ ATS1CPR
isb
@@ -424,13 +428,19 @@
lsl r2, r2, #4
orr r2, r2, r1, lsl #24
+ /* Restore PAR */
+ pop {r0, r1}
+ mcrr p15, 0, r0, r1, c7 @ PAR
+
3: load_vcpu @ Load VCPU pointer to r0
str r2, [r0, #VCPU_HPFAR]
1: mov r1, #ARM_EXCEPTION_HVC
b __kvm_vcpu_return
-4: pop {r0, r1, r2} @ Failed translation, return to guest
+4: pop {r0, r1} @ Failed translation, return to guest
+ mcrr p15, 0, r0, r1, c7 @ PAR
+ pop {r0, r1, r2}
eret
/*