blob: 41acaa1bc4da57647d41418e53b5cd19898950a7 [file] [log] [blame]
From 1d9b5f78665f25b6cd5188d958418914006c38ba Mon Sep 17 00:00:00 2001
From: Andrew Murray <>
Date: Fri, 17 Jan 2020 13:43:24 +0000
Subject: [PATCH] KVM: arm64: Write arch.mdcr_el2 changes since last vcpu_load
on VHE
commit 4942dc6638b07b5326b6d2faa142635c559e7cd5 upstream.
On VHE systems arch.mdcr_el2 is written to mdcr_el2 at vcpu_load time to
set options for self-hosted debug and the performance monitors
Unfortunately the value of arch.mdcr_el2 is not calculated until
kvm_arm_setup_debug() in the run loop after the vcpu has been loaded.
This means that the initial brief iterations of the run loop use a zero
value of mdcr_el2 - until the vcpu is preempted. This also results in a
delay between changes to vcpu->guest_debug taking effect.
Fix this by writing to mdcr_el2 in kvm_arm_setup_debug() on VHE systems
when a change to arch.mdcr_el2 has been detected.
Fixes: d5a21bcc2995 ("KVM: arm64: Move common VHE/non-VHE trap config in separate functions")
Cc: <> # 4.17.x-
Suggested-by: James Morse <>
Acked-by: Will Deacon <>
Reviewed-by: Marc Zyngier <>
Signed-off-by: Andrew Murray <>
Signed-off-by: Catalin Marinas <>
Signed-off-by: Paul Gortmaker <>
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 43487f035385..7a7e425616b5 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -101,7 +101,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
- unsigned long mdscr;
+ unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2;
trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
@@ -197,6 +197,10 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
+ /* Write mdcr_el2 changes since vcpu_load on VHE systems */
+ if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2)
+ write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));