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Date: Tue, 25 Nov 2014 16:10:02 +0000
From: Alex Bennée <alex.bennee@...aro.org>
To: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.cs.columbia.edu, christoffer.dall@...aro.org,
marc.zyngier@....com, peter.maydell@...aro.org, agraf@...e.de
Cc: jan.kiszka@...mens.com, dahi@...ux.vnet.ibm.com,
r65777@...escale.com, bp@...e.de, pbonzini@...hat.com,
Alex Bennée <alex.bennee@...aro.org>,
Gleb Natapov <gleb@...nel.org>,
Jonathan Corbet <corbet@....net>,
Russell King <linux@....linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
linux-doc@...r.kernel.org (open list:DOCUMENTATION),
linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 4/7] KVM: arm64: guest debug, add SW break point support
This adds support for SW breakpoints inserted by userspace.
First we need to trap all BKPT exceptions in the hypervisor (ELS). This
in controlled through the MDCR_EL2 register. I've added a new field to
the vcpu structure to hold this value. There should be scope to
rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
manipulation in later patches.
Once the exception arrives we triggers an exit from the main hypervisor
loop to the hypervisor controller. The kvm_debug_exit_arch carries the
address of the exception. If the controller doesn't know of breakpoint
then we have a guest inserted breakpoint and the hypervisor needs to
start again and deliver the exception to guest.
Signed-off-by: Alex Bennée <alex.bennee@...aro.org>
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 2c6386e..9383359 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2592,7 +2592,7 @@ when running. Common control bits are:
The top 16 bits of the control field are architecture specific control
flags which can include the following:
- - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86]
+ - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index a0ff410..48d26bb 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
struct kvm_guest_debug *dbg)
{
+ /* Route debug traps to el2? */
+ bool route_el2 = false;
+
/* If it's not enabled clear all flags */
if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
vcpu->guest_debug = 0;
@@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
/* Software Break Points */
if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
- kvm_info("SW BP support requested, not yet implemented\n");
- return -EINVAL;
+ kvm_info("SW BP support requested\n");
+ route_el2 = true;
}
/* Hardware assisted Break and Watch points */
@@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
return -EINVAL;
}
+ /* If we are going to handle any debug exceptions we need to
+ * set MDCE_EL2.TDE to ensure they are routed to the
+ * hypervisor. If userspace determines the exception was
+ * actually internal to the guest it needs to handle
+ * re-injecting the exception.
+ */
+ if (route_el2) {
+ kvm_info("routing debug exceptions");
+ vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
+ } else {
+ kvm_info("not routing debug exceptions");
+ vcpu->arch.mdcr_el2 = 0;
+ }
+
return 0;
}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2012c4b..38b0f07 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -98,6 +98,7 @@ struct kvm_vcpu_arch {
/* HYP configuration */
u64 hcr_el2;
+ u32 mdcr_el2;
/* Exception Information */
struct kvm_vcpu_fault_info fault;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 9a9fce0..8da1043 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -122,6 +122,7 @@ int main(void)
DEFINE(VCPU_HPFAR_EL2, offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
DEFINE(VCPU_DEBUG_FLAGS, offsetof(struct kvm_vcpu, arch.debug_flags));
DEFINE(VCPU_HCR_EL2, offsetof(struct kvm_vcpu, arch.hcr_el2));
+ DEFINE(VCPU_MDCR_EL2, offsetof(struct kvm_vcpu, arch.mdcr_el2));
DEFINE(VCPU_IRQ_LINES, offsetof(struct kvm_vcpu, arch.irq_lines));
DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
DEFINE(VCPU_TIMER_CNTV_CTL, offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 34b8bd0..28dc92b 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
return 1;
}
+/**
+ * kvm_handle_bkpt - handle a break-point instruction
+ *
+ * @vcpu: the vcpu pointer
+ *
+ * By definition if we arrive here it's because we are routing
+ * all SW breakpoints to the hyper-visor as some may be a result of
+ * guest debugging. If user-space decides this particular break-point
+ * isn't for the host to handle it can re-feed the exception to the
+ * guest.
+ */
+static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ run->exit_reason = KVM_EXIT_DEBUG;
+ run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
+ run->debug.arch.address = *vcpu_pc(vcpu);
+ kvm_info("exiting from %llx\n", run->debug.arch.address);
+ return 0;
+}
+
static exit_handle_fn arm_exit_handlers[] = {
[ESR_EL2_EC_WFI] = kvm_handle_wfx,
[ESR_EL2_EC_CP15_32] = kvm_handle_cp15_32,
@@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = {
[ESR_EL2_EC_SYS64] = kvm_handle_sys_reg,
[ESR_EL2_EC_IABT] = kvm_handle_guest_abort,
[ESR_EL2_EC_DABT] = kvm_handle_guest_abort,
+ [ESR_EL2_EC_BKPT32] = kvm_handle_bkpt,
+ [ESR_EL2_EC_BRK64] = kvm_handle_bkpt,
};
static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index b72aa9f..3c733ea 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -772,6 +772,10 @@
orr x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
orr x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
+ // Any other bits (currently TDE)
+ ldr x3, [x0, #VCPU_MDCR_EL2]
+ orr x2, x2, x3
+
// Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
// if not dirty.
ldr x3, [x0, #VCPU_DEBUG_FLAGS]
--
2.1.3
--
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