arm64: KVM: Enable access to TRBE support for host

For a nvhe host, the EL2 must allow the EL1&0 translation
regime for TraceBuffer (MDCR_EL2.E2TB == 0b11). This must
be saved/restored over a trip to the guest. Also, before
entering the guest, we must flush any trace data if the
TRBE was enabled. And we must prohibit the generation
of trace while we are in EL1 by clearing the TRFCR_EL1.

For vhe, the EL2 must prevent the EL1 access to the Trace
Buffer.

The MDCR_EL2 bit definitions for TRBE are available here :

  https://developer.arm.com/documentation/ddi0601/2020-12/AArch64-Registers/

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210405164307.1720226-8-suzuki.poulose@arm.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index e6ee9b7faec6..7d3f25868cae 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -52,11 +52,43 @@ static void __debug_restore_spe(u64 pmscr_el1)
 	write_sysreg_s(pmscr_el1, SYS_PMSCR_EL1);
 }
 
+static void __debug_save_trace(u64 *trfcr_el1)
+{
+	*trfcr_el1 = 0;
+
+	/* Check if the TRBE is enabled */
+	if (!(read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_ENABLE))
+		return;
+	/*
+	 * Prohibit trace generation while we are in guest.
+	 * Since access to TRFCR_EL1 is trapped, the guest can't
+	 * modify the filtering set by the host.
+	 */
+	*trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1);
+	write_sysreg_s(0, SYS_TRFCR_EL1);
+	isb();
+	/* Drain the trace buffer to memory */
+	tsb_csync();
+	dsb(nsh);
+}
+
+static void __debug_restore_trace(u64 trfcr_el1)
+{
+	if (!trfcr_el1)
+		return;
+
+	/* Restore trace filter controls */
+	write_sysreg_s(trfcr_el1, SYS_TRFCR_EL1);
+}
+
 void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 {
 	/* Disable and flush SPE data generation */
 	if (vcpu->arch.flags & KVM_ARM64_DEBUG_STATE_SAVE_SPE)
 		__debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1);
+	/* Disable and flush Self-Hosted Trace generation */
+	if (vcpu->arch.flags & KVM_ARM64_DEBUG_STATE_SAVE_TRBE)
+		__debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1);
 }
 
 void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
@@ -68,6 +100,8 @@ void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 {
 	if (vcpu->arch.flags & KVM_ARM64_DEBUG_STATE_SAVE_SPE)
 		__debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
+	if (vcpu->arch.flags & KVM_ARM64_DEBUG_STATE_SAVE_TRBE)
+		__debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1);
 }
 
 void __debug_switch_to_host(struct kvm_vcpu *vcpu)