From bb5e4e0c9c25872e22aeaf2f3c4cada511317c59 Mon Sep 17 00:00:00 2001 From: James Morse Date: Mon, 15 Jan 2018 19:39:00 +0000 Subject: [PATCH] KVM: arm/arm64: mask/unmask daif around VHE guests BugLink: http://bugs.launchpad.net/bugs/1756096 Non-VHE systems take an exception to EL2 in order to world-switch into the guest. When returning from the guest KVM implicitly restores the DAIF flags when it returns to the kernel at EL1. With VHE none of this exception-level jumping happens, so KVMs world-switch code is exposed to the host kernel's DAIF values, and KVM spills the guest-exit DAIF values back into the host kernel. On entry to a guest we have Debug and SError exceptions unmasked, KVM has switched VBAR but isn't prepared to handle these. On guest exit Debug exceptions are left disabled once we return to the host and will stay this way until we enter user space. Add a helper to mask/unmask DAIF around VHE guests. The unmask can only happen after the hosts VBAR value has been synchronised by the isb in __vhe_hyp_call (via kvm_call_hyp()). Masking could be as late as setting KVMs VBAR value, but is kept here for symmetry. Acked-by: Marc Zyngier Signed-off-by: James Morse Reviewed-by: Christoffer Dall Signed-off-by: Catalin Marinas (backported from commit 4f5abad9e826bd579b0661efa32682d9c9bc3fa8) Signed-off-by: Manoj Iyer Signed-off-by: Seth Forshee --- arch/arm/include/asm/kvm_host.h | 3 +++ arch/arm64/include/asm/kvm_host.h | 11 +++++++++++ virt/kvm/arm/arm.c | 4 ++++ 3 files changed, 18 insertions(+) diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h index fdd9da1555be..9d43d9d27884 100644 --- a/arch/arm/include/asm/kvm_host.h +++ b/arch/arm/include/asm/kvm_host.h @@ -301,6 +301,9 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu, /* All host FP/SIMD state is restored on guest exit, so nothing to save: */ static inline void kvm_fpsimd_flush_cpu_state(void) {} +static inline void kvm_arm_vhe_guest_enter(void) {} +static inline void kvm_arm_vhe_guest_exit(void) {} + static inline bool kvm_arm_harden_branch_predictor(void) { /* No way to detect it yet, pretend it is not there. */ diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 5466710a3780..f1882bd70e32 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -398,6 +399,16 @@ static inline void kvm_fpsimd_flush_cpu_state(void) sve_flush_cpu_state(); } +static inline void kvm_arm_vhe_guest_enter(void) +{ + local_daif_mask(); +} + +static inline void kvm_arm_vhe_guest_exit(void) +{ + local_daif_restore(DAIF_PROCCTX_NOIRQ); +} + static inline bool kvm_arm_harden_branch_predictor(void) { return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR); diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index c2e055eb5e18..f065cfe1c1db 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -704,9 +704,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) */ trace_kvm_entry(*vcpu_pc(vcpu)); guest_enter_irqoff(); + if (has_vhe()) + kvm_arm_vhe_guest_enter(); ret = kvm_call_hyp(__kvm_vcpu_run, vcpu); + if (has_vhe()) + kvm_arm_vhe_guest_exit(); vcpu->mode = OUTSIDE_GUEST_MODE; vcpu->stat.exits++; /* -- 2.39.5