KVM: arm: introduce kvm_arm_init/setup/clear_debug

This is a precursor for later patches which will need to do more to
setup debug state before entering the hyp.S switch code. The existing
functionality for setting mdcr_el2 has been moved out of hyp.S and now
uses the value kept in vcpu->arch.mdcr_el2.

As the assembler used to previously mask and preserve MDCR_EL2.HPMN I've
had to add a mechanism to save the value of mdcr_el2 as a per-cpu
variable during the initialisation code. The kernel never sets this
number so we are assuming the bootcode has set up the correct value
here.

This also moves the conditional setting of the TDA bit from the hyp code
into the C code which is currently used for the lazy debug register
context switch code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index e896d2c196e63b79365e6f637c7b697c56c48f71..2b0bc8c5755288eae965cbad806f2b740c9526e2 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -231,4 +231,8 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 
+static inline void kvm_arm_init_debug(void) {}
+static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
+static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
+
 #endif /* __ARM_KVM_HOST_H__ */

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 1b693cb2d5b277452e36344fc23af5a07a85a7ca..77151b111d32d3f6c00b6d7fd2e4516a0fb59211 100644 (file)
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -543,6 +543,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
                        continue;
                }
 
+               kvm_arm_setup_debug(vcpu);
+
                /**************************************************************
                 * Enter the guest
                 */
@@ -557,6 +559,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
                 * Back from guest
                 *************************************************************/
 
+               kvm_arm_clear_debug(vcpu);
+
                /*
                 * We may have taken a host interrupt in HYP mode (ie
                 * while executing the guest). This interrupt is still
@@ -914,6 +918,8 @@ static void cpu_init_hyp_mode(void *dummy)
        vector_ptr = (unsigned long)__kvm_hyp_vector;
 
        __cpu_init_hyp_mode(boot_pgd_ptr, pgd_ptr, hyp_stack_ptr, vector_ptr);
+
+       kvm_arm_init_debug();
 }
 
 static int hyp_init_cpu_notify(struct notifier_block *self,

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 3c5fe685a2d69a55daf68fe40fa782a0843bb2f5..f5e40dae291ab2c20a6af7a98b154bc74af627f5 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -132,6 +132,8 @@ extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern u64 __vgic_v3_get_ich_vtr_el2(void);
 
+extern u32 __kvm_get_mdcr_el2(void);
+
 #endif
 
 #endif /* __ARM_KVM_ASM_H__ */

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2709db2a7eac78a49fc75c072810b9ac41cc9e0a..c90c6a41c448c0410b1f5e0d4efff32dfdb1e103 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -103,6 +103,7 @@ struct kvm_vcpu_arch {
 
        /* HYP configuration */
        u64 hcr_el2;
+       u32 mdcr_el2;
 
        /* Exception Information */
        struct kvm_vcpu_fault_info fault;
@@ -227,4 +228,8 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 
+void kvm_arm_init_debug(void);
+void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
+void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
+
 #endif /* __ARM64_KVM_HOST_H__ */

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index c99701a34d7b3c9238c80e1e4ebbaeba6e3488c3..5c900d49b90683ebd6f684a6663761d543c2842c 100644 (file)
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -117,6 +117,7 @@ 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/Makefile b/arch/arm64/kvm/Makefile
index f90f4aa7f88d9d60ba4e8b53645c7d81d15f3e07..1949fe5f54246a3f14983753570f4e4d0f978e76 100644 (file)
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -17,7 +17,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(ARM)/psci.o $(ARM)/perf.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += emulate.o inject_fault.o regmap.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
-kvm-$(CONFIG_KVM_ARM_HOST) += guest.o reset.o sys_regs.o sys_regs_generic_v8.o
+kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic-v2.o

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
new file mode 100644 (file)
index 0000000..faf0e1f
--- /dev/null
+++ b/arch/arm64/kvm/debug.c
@@ -0,0 +1,81 @@
+/*
+ * Debug and Guest Debug support
+ *
+ * Copyright (C) 2015 - Linaro Ltd
+ * Author: Alex Bennée <alex.bennee@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_arm.h>
+
+static DEFINE_PER_CPU(u32, mdcr_el2);
+
+/**
+ * kvm_arm_init_debug - grab what we need for debug
+ *
+ * Currently the sole task of this function is to retrieve the initial
+ * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
+ * presumably been set-up by some knowledgeable bootcode.
+ *
+ * It is called once per-cpu during CPU hyp initialisation.
+ */
+
+void kvm_arm_init_debug(void)
+{
+       __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
+}
+
+
+/**
+ * kvm_arm_setup_debug - set up debug related stuff
+ *
+ * @vcpu:      the vcpu pointer
+ *
+ * This is called before each entry into the hypervisor to setup any
+ * debug related registers. Currently this just ensures we will trap
+ * access to:
+ *  - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
+ *  - Debug ROM Address (MDCR_EL2_TDRA)
+ *  - OS related registers (MDCR_EL2_TDOSA)
+ *
+ * Additionally, KVM only traps guest accesses to the debug registers if
+ * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
+ * flag on vcpu->arch.debug_flags).  Since the guest must not interfere
+ * with the hardware state when debugging the guest, we must ensure that
+ * trapping is enabled whenever we are debugging the guest using the
+ * debug registers.
+ */
+
+void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
+{
+       bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
+
+       vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
+       vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
+                               MDCR_EL2_TPMCR |
+                               MDCR_EL2_TDRA |
+                               MDCR_EL2_TDOSA);
+
+       /* Trap on access to debug registers? */
+       if (trap_debug)
+               vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
+
+}
+
+void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
+{
+       /* Nothing to do yet */
+}

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 17a8fb14f428d47226edbeeb661e840ff53b8988..b3176e6e51d15fb66169ac640fdd4b3dfeeb17b8 100644 (file)
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -770,17 +770,8 @@
        mov     x2, #(1 << 15)  // Trap CP15 Cr=15
        msr     hstr_el2, x2
 
-       mrs     x2, mdcr_el2
-       and     x2, x2, #MDCR_EL2_HPMN_MASK
-       orr     x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
-       orr     x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
-
-       // Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
-       // if not dirty.
-       ldr     x3, [x0, #VCPU_DEBUG_FLAGS]
-       tbnz    x3, #KVM_ARM64_DEBUG_DIRTY_SHIFT, 1f
-       orr     x2, x2,  #MDCR_EL2_TDA
-1:
+       // Monitor Debug Config - see kvm_arm_setup_debug()
+       ldr     x2, [x0, #VCPU_MDCR_EL2]
        msr     mdcr_el2, x2
 .endm
 
@@ -1285,4 +1276,10 @@ ENTRY(__kvm_hyp_vector)
        ventry  el1_error_invalid               // Error 32-bit EL1
 ENDPROC(__kvm_hyp_vector)
 
+
+ENTRY(__kvm_get_mdcr_el2)
+       mrs     x0, mdcr_el2
+       ret
+ENDPROC(__kvm_get_mdcr_el2)
+
        .popsection