On Tue, May 22, 2018 at 04:06:47PM +0100, Marc Zyngier wrote: > In order to forward the guest's ARCH_WORKAROUND_2 calls to EL3, > add a small(-ish) sequence to handle it at EL2. Special care must > be taken to track the state of the guest itself by updating the > workaround flags. We also rely on patching to enable calls into > the firmware. > > Note that since we need to execute branches, this always executes > after the Spectre-v2 mitigation has been applied. > > Signed-off-by: Marc Zyngier <[email protected]> > --- > arch/arm64/kernel/asm-offsets.c | 1 + > arch/arm64/kvm/hyp/hyp-entry.S | 38 +++++++++++++++++++++++++++++++++++++- > 2 files changed, 38 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 5bdda651bd05..323aeb5f2fe6 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -136,6 +136,7 @@ int main(void) > #ifdef CONFIG_KVM_ARM_HOST > DEFINE(VCPU_CONTEXT, offsetof(struct kvm_vcpu, arch.ctxt)); > DEFINE(VCPU_FAULT_DISR, offsetof(struct kvm_vcpu, arch.fault.disr_el1)); > + DEFINE(VCPU_WORKAROUND_FLAGS, offsetof(struct kvm_vcpu, > arch.workaround_flags)); > DEFINE(CPU_GP_REGS, offsetof(struct kvm_cpu_context, > gp_regs)); > DEFINE(CPU_USER_PT_REGS, offsetof(struct kvm_regs, regs)); > DEFINE(CPU_FP_REGS, offsetof(struct kvm_regs, fp_regs)); > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > index bffece27b5c1..5b1fa37ca1f4 100644 > --- a/arch/arm64/kvm/hyp/hyp-entry.S > +++ b/arch/arm64/kvm/hyp/hyp-entry.S > @@ -106,8 +106,44 @@ el1_hvc_guest: > */ > ldr x1, [sp] // Guest's x0 > eor w1, w1, #ARM_SMCCC_ARCH_WORKAROUND_1 > + cbz w1, wa_epilogue > + > + /* ARM_SMCCC_ARCH_WORKAROUND_2 handling */ > + eor w1, w1, #(ARM_SMCCC_ARCH_WORKAROUND_1 ^ \ > + ARM_SMCCC_ARCH_WORKAROUND_2)
... that took me a second. Lovely. :) > cbnz w1, el1_trap > - mov x0, x1 > + > +#ifdef CONFIG_ARM64_SSBD > +alternative_cb arm64_enable_wa2_handling > + b wa2_end > +alternative_cb_end > + get_vcpu_ptr x2, x0 > + ldr x0, [x2, #VCPU_WORKAROUND_FLAGS] > + > + /* Sanitize the argument and update the guest flags*/ Nit: space before the trailing '*/'. Either that or use a '//' comment. Otherwise, this looks fine, so with that fixed: Reviewed-by: Mark Rutland <[email protected]> Mark. > + ldr x1, [sp, #8] // Guest's x1 > + clz w1, w1 // Murphy's device: > + lsr w1, w1, #5 // w1 = !!w1 without using > + eor w1, w1, #1 // the flags... > + bfi x0, x1, #VCPU_WORKAROUND_2_FLAG_SHIFT, #1 > + str x0, [x2, #VCPU_WORKAROUND_FLAGS] > + > + /* Check that we actually need to perform the call */ > + hyp_ldr_this_cpu x0, arm64_ssbd_callback_required, x2 > + cbz x0, wa2_end > + > + mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2 > + smc #0 > + > + /* Don't leak data from the SMC call */ > + mov x3, xzr > +wa2_end: > + mov x2, xzr > + mov x1, xzr > +#endif > + > +wa_epilogue: > + mov x0, xzr > add sp, sp, #16 > eret > > -- > 2.14.2 >
