[PATCH v2 4/9] arm64: KVM: Make unexpected reads from WO registers inject an undef

Marc Zyngier
2017-03-27T16:02:09Z

Reads from write-only system registers are generally confined to
EL1 and not propagated to EL2 (that's what the architecture
mantates). In order to be sure that we have a sane behaviour
even in the unlikely event that we have a broken system, we still
handle it in KVM.

In that case, let's inject an undef into the guest.

Let's also remove write_to_read_only which isn't used anywhere.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kvm/sys_regs.c | 9 +++++++++
arch/arm64/kvm/sys_regs.h | 18 ------------------
2 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 5e3ce7890b35..19a036b4f6ac 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -55,6 +55,15 @@
* 64bit interface.
*/

+static bool read_from_write_only(struct kvm_vcpu *vcpu,
+ const struct sys_reg_params *params)
+{
+ WARN_ONCE(1, "Unexpected sys_reg read to write-only register\n");
+ print_sys_reg_instr(params);
+ kvm_inject_undefined(vcpu);
+ return false;
+}
+
/* 3 bits per cache level, as per CLIDR, but non-existent caches always 0 */
static u32 cache_levels;

diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index 9c6ffd0f0196..638f724e45af 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -83,24 +83,6 @@ static inline bool read_zero(struct kvm_vcpu *vcpu,
return true;
}

-static inline bool write_to_read_only(struct kvm_vcpu *vcpu,
- const struct sys_reg_params *params)
-{
- kvm_debug("sys_reg write to read-only register at: %lx\n",
- *vcpu_pc(vcpu));
- print_sys_reg_instr(params);
- return false;
-}
-
-static inline bool read_from_write_only(struct kvm_vcpu *vcpu,
- const struct sys_reg_params *params)
-{
- kvm_debug("sys_reg read to write-only register at: %lx\n",
- *vcpu_pc(vcpu));
- print_sys_reg_instr(params);
- return false;
-}
-
/* Reset functions */
static inline void reset_unknown(struct kvm_vcpu *vcpu,
const struct sys_reg_desc *r)
--
2.11.0