[PATCH v3 10/12] KVM: arm64: trap nested debug register access
From: Christoffer Dall <hidden>
Date: 2015-05-08 16:46:50
Also in:
kvm, kvmarm, lkml
On Thu, May 07, 2015 at 10:07:13AM +0100, Alex Benn?e wrote:
quoted hunk ↗ jump to hunk
When we are using the hardware registers for guest debug we need to deal with the guests access to them. There is already a mechanism for dealing with these accesses so we build on top of that. - any access to mdscr_el1 is now stored in the mirror location - access to DBG[WB][CV]R continues to go to guest's context There is one register (MDCCINT_EL1) which guest debug doesn't care about so this behaves as before. Signed-off-by: Alex Benn?e <redacted> --- v3 - re-factor for better flow and fall through. - much simpler with debug_ptr (use the guest area as before) - tweak shadow fn to avoid multi-line ifdiff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a44fb32..7aa3b3a 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h@@ -132,7 +132,13 @@ struct kvm_vcpu_arch { * here. */ - /* Guest registers we preserve during guest debugging */ + /* + * Guest registers we preserve during guest debugging. + * + * These shadow registers are updated by the kvm_handle_sys_reg + * trap handler if the guest accesses or updates them while we + * are using guest debug. + */ struct { u32 pstate; u32 mdscr_el1;diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index 1ab63dd..dc8bca8 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c@@ -50,8 +50,7 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu) { *vcpu_cpsr(vcpu) |= (vcpu->arch.guest_debug_state.pstate & SPSR_DEBUG_MASK); - vcpu_sys_reg(vcpu, MDSCR_EL1) |= - (vcpu->arch.guest_debug_state.mdscr_el1 & MDSCR_EL1_DEBUG_MASK); + vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_state.mdscr_el1; } /**diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index c370b40..95f422f 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c@@ -196,11 +196,40 @@ static bool trap_dbgauthstatus_el1(struct kvm_vcpu *vcpu, * - If the dirty bit is set, save guest registers, restore host * registers and clear the dirty bit. This ensure that the host can * now use the debug registers. + * + * We also use this mechanism to set-up the debug registers for guest
s/set-up/set up/
+ * debugging. If this is the case we want to ensure the guest sees
If this is the case, (comma)
+ * the right versions of the registers - even if they are not going to
+ * be effective while guest debug is using HW debug.
+ *
*/
+
+static bool shadow_debug_reg(struct kvm_vcpu *vcpu,
+ const struct sys_reg_params *p,
+ const struct sys_reg_desc *r)
+{
+ /* MDSCR_EL1 */
+ if (r->reg == MDSCR_EL1) {
+ u32 *shadow_mdscr_el1 = &vcpu->arch.guest_debug_state.mdscr_el1;
+
+ if (p->is_write)
+ *shadow_mdscr_el1 = *vcpu_reg(vcpu, p->Rt);
+ else
+ *vcpu_reg(vcpu, p->Rt) = *shadow_mdscr_el1;
+
+ return true;
+ }
+
+ return false;
+}
+
static bool trap_debug_regs(struct kvm_vcpu *vcpu,
const struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
+ if (vcpu->guest_debug && shadow_debug_reg(vcpu, p, r))
+ return true;
+so do we also have a MDSCR_EL1 in sys_regs and one in guest_debug_state now? If yes, what are the differences between the two?
if (p->is_write) {
vcpu_sys_reg(vcpu, r->reg) = *vcpu_reg(vcpu, p->Rt);
vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
--
2.3.5Thanks, -Christoffer