arm64: Add workaround for Arm Cortex-A77 erratum 1508412

On Cortex-A77 r0p0 and r1p0, a sequence of a non-cacheable or device load
and a store exclusive or PAR_EL1 read can cause a deadlock.

The workaround requires a DMB SY before and after a PAR_EL1 register
read. In addition, it's possible an interrupt (doing a device read) or
KVM guest exit could be taken between the DMB and PAR read, so we
also need a DMB before returning from interrupt and before returning to
a guest.

A deadlock is still possible with the workaround as KVM guests must also
have the workaround. IOW, a malicious guest can deadlock an affected
systems.

This workaround also depends on a firmware counterpart to enable the h/w
to insert DMB SY after load and store exclusive instructions. See the
errata document SDEN-1152370 v10 [1] for more information.

[1] https://static.docs.arm.com/101992/0010/Arm_Cortex_A77_MP074_Software_Developer_Errata_Notice_v10.pdf

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: kvmarm@lists.cs.columbia.edu
Link: https://lore.kernel.org/r/20201028182839.166037-2-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

2 files changed, 14 insertions, 9 deletions

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 313a8fa3c721..1f875a8f20c4 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -140,9 +140,9 @@ static inline bool __translate_far_to_hpfar(u64 far, u64 *hpfar)
 	 * We do need to save/restore PAR_EL1 though, as we haven't
 	 * saved the guest context yet, and we may return early...
 	 */
-	par = read_sysreg(par_el1);
+	par = read_sysreg_par();
 	if (!__kvm_at("s1e1r", far))
-		tmp = read_sysreg(par_el1);
+		tmp = read_sysreg_par();
 	else
 		tmp = SYS_PAR_EL1_F; /* back to the guest */
 	write_sysreg(par, par_el1);
@@ -421,7 +421,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) &&
 	    kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 &&
 	    handle_tx2_tvm(vcpu))
-		return true;
+		goto guest;
 
 	/*
 	 * We trap the first access to the FP/SIMD to save the host context
@@ -431,13 +431,13 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 	 * Similarly for trapped SVE accesses.
 	 */
 	if (__hyp_handle_fpsimd(vcpu))
-		return true;
+		goto guest;
 
 	if (__hyp_handle_ptrauth(vcpu))
-		return true;
+		goto guest;
 
 	if (!__populate_fault_info(vcpu))
-		return true;
+		goto guest;
 
 	if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
 		bool valid;
@@ -452,7 +452,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 			int ret = __vgic_v2_perform_cpuif_access(vcpu);
 
 			if (ret == 1)
-				return true;
+				goto guest;
 
 			/* Promote an illegal access to an SError.*/
 			if (ret == -1)
@@ -468,12 +468,17 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 		int ret = __vgic_v3_perform_cpuif_access(vcpu);
 
 		if (ret == 1)
-			return true;
+			goto guest;
 	}
 
 exit:
 	/* Return to the host kernel and handle the exit */
 	return false;
+
+guest:
+	/* Re-enter the guest */
+	asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));
+	return true;
 }
 
 static inline void __kvm_unexpected_el2_exception(void)
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index 7a986030145f..cce43bfe158f 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -43,7 +43,7 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, CONTEXTIDR_EL1) = read_sysreg_el1(SYS_CONTEXTIDR);
 	ctxt_sys_reg(ctxt, AMAIR_EL1)	= read_sysreg_el1(SYS_AMAIR);
 	ctxt_sys_reg(ctxt, CNTKCTL_EL1)	= read_sysreg_el1(SYS_CNTKCTL);
-	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg(par_el1);
+	ctxt_sys_reg(ctxt, PAR_EL1)	= read_sysreg_par();
 	ctxt_sys_reg(ctxt, TPIDR_EL1)	= read_sysreg(tpidr_el1);
 
 	ctxt_sys_reg(ctxt, SP_EL1)	= read_sysreg(sp_el1);