Re: [PATCH v8 5/9] KVM: arm/arm64: preserve host MDCR_EL2 value

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Hi,

On 4/5/19 4:32 PM, Dave Martin wrote:
On Tue, Apr 02, 2019 at 07:57:13AM +0530, Amit Daniel Kachhap wrote:
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@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
---

Changes since v7:
* Removed unused function __kvm_get_mdcr_el2 [Kristina].

  arch/arm/include/asm/kvm_host.h   |  1 -
  arch/arm64/include/asm/kvm_asm.h  |  2 --
  arch/arm64/include/asm/kvm_host.h |  6 ++----
  arch/arm64/include/asm/kvm_hyp.h  |  2 +-
  arch/arm64/kvm/debug.c            | 28 ++++++----------------------
  arch/arm64/kvm/hyp/debug-sr.c     |  5 -----
  arch/arm64/kvm/hyp/switch.c       | 18 +++++-------------
  arch/arm64/kvm/hyp/sysreg-sr.c    |  8 +++++++-
  virt/kvm/arm/arm.c                |  1 -
  9 files changed, 21 insertions(+), 50 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 6d0aac4..a928565 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -343,7 +343,6 @@ 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_asm.h b/arch/arm64/include/asm/kvm_asm.h
index a68205c..a15ba55 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -78,8 +78,6 @@ extern u64 __vgic_v3_read_vmcr(void);
  extern void __vgic_v3_write_vmcr(u32 vmcr);
  extern void __vgic_v3_init_lrs(void);
-extern u32 __kvm_get_mdcr_el2(void);
-
  extern void __kvm_populate_host_regs(void);
/*
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3b09fd0..e3ccd7b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -211,6 +211,8 @@ struct kvm_cpu_context {
/* HYP host/guest configuration */
  	u64 hcr_el2;
+	u32 mdcr_el2;
+
  	struct kvm_vcpu *__hyp_running_vcpu;
  };
@@ -226,9 +228,6 @@ struct vcpu_reset_state {
  struct kvm_vcpu_arch {
  	struct kvm_cpu_context ctxt;
- /* HYP configuration */
-	u32 mdcr_el2;
-
  	/* Exception Information */
  	struct kvm_vcpu_fault_info fault;
@@ -498,7 +497,6 @@ 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/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 4da765f..7fcde8a 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -152,7 +152,7 @@ void __fpsimd_restore_state(struct user_fpsimd_state *fp_regs);
  bool __fpsimd_enabled(void);
void activate_traps_vhe_load(struct kvm_vcpu *vcpu);
-void deactivate_traps_vhe_put(void);
+void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu);
u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
  void __noreturn __hyp_do_panic(unsigned long, ...);
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index fd917d6..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_ret(__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/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
index 5000976..f49a3f7 100644
--- a/arch/arm64/kvm/hyp/debug-sr.c
+++ b/arch/arm64/kvm/hyp/debug-sr.c
@@ -198,8 +198,3 @@ void __hyp_text __debug_switch_to_host(struct kvm_vcpu *vcpu)
vcpu->arch.flags &= ~KVM_ARM64_DEBUG_DIRTY;
  }
-
-u32 __hyp_text __kvm_get_mdcr_el2(void)
-{
-	return read_sysreg(mdcr_el2);
-}
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index f5cefa1..fe76e24 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -84,7 +84,7 @@ 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)
@@ -161,15 +161,11 @@ NOKPROBE_SYMBOL(deactivate_traps_vhe);
static void __hyp_text __deactivate_traps_nvhe(struct kvm_cpu_context *host_ctxt)
  {
-	u64 mdcr_el2 = read_sysreg(mdcr_el2);
  	struct kvm_cpu_context *hyp_host_ctxt = kern_hyp_va(host_ctxt);
__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(hyp_host_ctxt->mdcr_el2, mdcr_el2);
  	write_sysreg(hyp_host_ctxt->hcr_el2, hcr_el2);
  	write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
  }
@@ -199,15 +195,11 @@ void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
  	__activate_traps_common(vcpu);
  }
-void deactivate_traps_vhe_put(void)
+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 277f82b..6afd309 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -298,7 +298,7 @@ void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu)
  	if (!has_vhe())
  		return;
- deactivate_traps_vhe_put();
+	deactivate_traps_vhe_put(vcpu);
__sysreg_save_el1_state(guest_ctxt);
  	__sysreg_save_user_state(guest_ctxt);
@@ -333,4 +333,10 @@ 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 e8c2ee6..58de0ca 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1322,7 +1322,6 @@ static void cpu_hyp_reinit(void)
  	else
  		cpu_init_hyp_mode(NULL);
- kvm_arm_init_debug();
  	cpu_init_host_ctxt();
if (vgic_present)

Looks reasonable overall.

I was wondering whether it would make sense to move some masking into
__kvm_populate_host_regs(), but probably not.

Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>
Thanks for the review.

Thanks,
Amit D.

Cheers
---Dave


--
2.7.4

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