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Subject[PATCH v6 2/6] arm64/kvm: preserve host MDCR_EL2 value
Date
Save host MDCR_EL2 value during kvm HYP initialisation and restore
after every switch from host to guest. There should not be any
change in functionality due to this.

The value of mdcr_el2 is now stored in struct kvm_cpu_context as
both host and guest can now use this field in a common way.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
arch/arm/include/asm/kvm_host.h | 1 -
arch/arm64/include/asm/kvm_host.h | 6 ++----
arch/arm64/kvm/debug.c | 28 ++++++----------------------
arch/arm64/kvm/hyp/switch.c | 17 ++++-------------
arch/arm64/kvm/hyp/sysreg-sr.c | 6 ++++++
virt/kvm/arm/arm.c | 1 -
6 files changed, 18 insertions(+), 41 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 05706b4..704667e 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -294,7 +294,6 @@ 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_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}

-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) {}
static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1b2e05b..2f1bb86 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -205,6 +205,8 @@ struct kvm_cpu_context {

/* HYP host/guest configuration */
u64 hcr_el2;
+ u32 mdcr_el2;
+
struct kvm_vcpu *__hyp_running_vcpu;
};

@@ -213,9 +215,6 @@ typedef struct kvm_cpu_context kvm_cpu_context_t;
struct kvm_vcpu_arch {
struct kvm_cpu_context ctxt;

- /* HYP configuration */
- u32 mdcr_el2;
-
/* Exception Information */
struct kvm_vcpu_fault_info fault;

@@ -446,7 +445,6 @@ 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_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}

-void kvm_arm_init_debug(void);
void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index f39801e..99dc0a4 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -32,8 +32,6 @@
DBG_MDSCR_KDE | \
DBG_MDSCR_MDE)

-static DEFINE_PER_CPU(u32, mdcr_el2);
-
/**
* save/restore_guest_debug_regs
*
@@ -65,21 +63,6 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
}

/**
- * 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_reset_debug_ptr - reset the debug ptr to point to the vcpu state
*/

@@ -111,6 +94,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)

void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
{
+ kvm_cpu_context_t *host_cxt = this_cpu_ptr(&kvm_host_cpu_state);
bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
unsigned long mdscr;

@@ -120,8 +104,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
* This also clears MDCR_EL2_E2PB_MASK to disable guest access
* to the profiling buffer.
*/
- vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
- vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
+ vcpu->arch.ctxt.mdcr_el2 = host_cxt->mdcr_el2 & MDCR_EL2_HPMN_MASK;
+ vcpu->arch.ctxt.mdcr_el2 |= (MDCR_EL2_TPM |
MDCR_EL2_TPMS |
MDCR_EL2_TPMCR |
MDCR_EL2_TDRA |
@@ -130,7 +114,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
/* Is Guest debugging in effect? */
if (vcpu->guest_debug) {
/* Route all software debug exceptions to EL2 */
- vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
+ vcpu->arch.ctxt.mdcr_el2 |= MDCR_EL2_TDE;

/* Save guest debug state */
save_guest_debug_regs(vcpu);
@@ -202,13 +186,13 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)

/* Trap debug register access */
if (trap_debug)
- vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
+ vcpu->arch.ctxt.mdcr_el2 |= MDCR_EL2_TDA;

/* If KDE or MDE are set, perform a full save/restore cycle. */
if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;

- trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
+ trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.ctxt.mdcr_el2);
trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
}

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 006bd33..03b36f1 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -82,7 +82,7 @@ static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
*/
write_sysreg(0, pmselr_el0);
write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
- write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
+ write_sysreg(vcpu->arch.ctxt.mdcr_el2, mdcr_el2);
}

static void __hyp_text __deactivate_traps_common(void)
@@ -157,14 +157,9 @@ static void deactivate_traps_vhe(struct kvm_cpu_context *host_ctxt)

static void __hyp_text __deactivate_traps_nvhe(struct kvm_cpu_context *host_ctxt)
{
- u64 mdcr_el2 = read_sysreg(mdcr_el2);
-
__deactivate_traps_common();

- mdcr_el2 &= MDCR_EL2_HPMN_MASK;
- mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
-
- write_sysreg(mdcr_el2, mdcr_el2);
+ write_sysreg(host_ctxt->mdcr_el2, mdcr_el2);
write_sysreg(host_ctxt->hcr_el2, hcr_el2);
write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
}
@@ -196,13 +191,9 @@ void activate_traps_vhe_load(struct kvm_vcpu *vcpu)

void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu)
{
- u64 mdcr_el2 = read_sysreg(mdcr_el2);
-
- mdcr_el2 &= MDCR_EL2_HPMN_MASK |
- MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT |
- MDCR_EL2_TPMS;
+ struct kvm_cpu_context *host_ctxt = vcpu->arch.host_cpu_context;

- write_sysreg(mdcr_el2, mdcr_el2);
+ write_sysreg(host_ctxt->mdcr_el2, mdcr_el2);

__deactivate_traps_common();
}
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 68ddc0f..42ec50f 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -334,4 +334,10 @@ void __hyp_text __kvm_populate_host_regs(void)
host_ctxt = __hyp_this_cpu_ptr(kvm_host_cpu_state);

host_ctxt->hcr_el2 = read_sysreg(hcr_el2);
+ /*
+ * Retrieve the initial value of mdcr_el2 so we can preserve
+ * MDCR_EL2.HPMN which has presumably been set-up by some
+ * knowledgeable bootcode.
+ */
+ host_ctxt->mdcr_el2 = read_sysreg(mdcr_el2);
}
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 8e18f7f..2032a66 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1327,7 +1327,6 @@ static void cpu_hyp_reinit(void)
else
cpu_init_hyp_mode(NULL);

- kvm_arm_init_debug();
__cpu_copy_hyp_conf();

if (vgic_present)
--
2.7.4
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