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KVM: arm: introduce kvm_arm_init/setup/clear_debug

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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>
This commit is contained in:
Alex Bennée 2015-07-07 17:29:56 +01:00 committed by Marc Zyngier
parent 0e6f07f29c
commit 56c7f5e77f
8 changed files with 108 additions and 12 deletions
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4
arch/arm/include/asm/kvm_host.h
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@ -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__ */

6
arch/arm/kvm/arm.c
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@ -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,

2
arch/arm64/include/asm/kvm_asm.h
View File

@ -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__ */

5
arch/arm64/include/asm/kvm_host.h
View File

@ -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__ */

1
arch/arm64/kernel/asm-offsets.c
View File

@ -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));

2
arch/arm64/kvm/Makefile
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@ -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

81
arch/arm64/kvm/debug.c Normal file
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@ -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 */
}

19
arch/arm64/kvm/hyp.S
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@ -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