linux-kernel - [RFC PATCH v2 11/38] KVM: arm64: Set vcpu context depending on the guest exception level

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Date:   Tue, 18 Jul 2017 11:58:37 -0500
From:   Jintack Lim <jintack.lim@...aro.org>
To:     kvmarm@...ts.cs.columbia.edu, christoffer.dall@...aro.org,
        marc.zyngier@....com
Cc:     corbet@....net, pbonzini@...hat.com, rkrcmar@...hat.com,
        linux@...linux.org.uk, catalin.marinas@....com,
        will.deacon@....com, akpm@...ux-foundation.org, mchehab@...nel.org,
        cov@...eaurora.org, daniel.lezcano@...aro.org,
        david.daney@...ium.com, mark.rutland@....com,
        suzuki.poulose@....com, stefan@...lo-penguin.com,
        andy.gross@...aro.org, wcohen@...hat.com,
        ard.biesheuvel@...aro.org, shankerd@...eaurora.org,
        vladimir.murzin@....com, james.morse@....com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Jintack Lim <jintack.lim@...aro.org>
Subject: [RFC PATCH v2 11/38] KVM: arm64: Set vcpu context depending on the guest exception level

If the guest exception level is EL2, then set up the shadow context of
the virtual EL2 to hardware. Otherwise, set the regular EL0/EL1 context.

Note that the shadow context content will be prepared in subsequent
patches.

Signed-off-by: Jintack Lim <jintack.lim@...aro.org>
---
 arch/arm64/kvm/context.c | 74 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/context.c b/arch/arm64/kvm/context.c
index bc43e66..2645787 100644
--- a/arch/arm64/kvm/context.c
+++ b/arch/arm64/kvm/context.c
@@ -18,11 +18,29 @@
 #include <linux/kvm_host.h>
 #include <asm/kvm_emulate.h>
 
-/**
- * kvm_arm_setup_shadow_state -- prepare shadow state based on emulated mode
- * @vcpu: The VCPU pointer
- */
-void kvm_arm_setup_shadow_state(struct kvm_vcpu *vcpu)
+static void flush_shadow_special_regs(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
+
+	ctxt->hw_pstate = *vcpu_cpsr(vcpu) & ~PSR_MODE_MASK;
+	/*
+	 * We can emulate the guest's configuration of which
+	 * stack pointer to use when executing in virtual EL2 by
+	 * using the equivalent feature in EL1 to point to
+	 * either the EL1 or EL0 stack pointer.
+	 */
+	if ((*vcpu_cpsr(vcpu) & PSR_MODE_MASK) == PSR_MODE_EL2h)
+		ctxt->hw_pstate |= PSR_MODE_EL1h;
+	else
+		ctxt->hw_pstate |= PSR_MODE_EL1t;
+
+	ctxt->hw_sys_regs = ctxt->shadow_sys_regs;
+	ctxt->hw_sp_el1 = vcpu_el2_sreg(vcpu, SP_EL2);
+	ctxt->hw_elr_el1 = vcpu_el2_sreg(vcpu, ELR_EL2);
+	ctxt->hw_spsr_el1 = vcpu_el2_sreg(vcpu, SPSR_EL2);
+}
+
+static void flush_special_regs(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
 
@@ -33,11 +51,18 @@ void kvm_arm_setup_shadow_state(struct kvm_vcpu *vcpu)
 	ctxt->hw_spsr_el1 = ctxt->gp_regs.spsr[KVM_SPSR_EL1];
 }
 
-/**
- * kvm_arm_restore_shadow_state -- write back shadow state from guest
- * @vcpu: The VCPU pointer
- */
-void kvm_arm_restore_shadow_state(struct kvm_vcpu *vcpu)
+static void sync_shadow_special_regs(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
+
+	*vcpu_cpsr(vcpu) &= PSR_MODE_MASK;
+	*vcpu_cpsr(vcpu) |= ctxt->hw_pstate & ~PSR_MODE_MASK;
+	vcpu_el2_sreg(vcpu, SP_EL2) = ctxt->hw_sp_el1;
+	vcpu_el2_sreg(vcpu, ELR_EL2) = ctxt->hw_elr_el1;
+	vcpu_el2_sreg(vcpu, SPSR_EL2) = ctxt->hw_spsr_el1;
+}
+
+static void sync_special_regs(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
 
@@ -47,6 +72,35 @@ void kvm_arm_restore_shadow_state(struct kvm_vcpu *vcpu)
 	ctxt->gp_regs.spsr[KVM_SPSR_EL1] = ctxt->hw_spsr_el1;
 }
 
+/**
+ * kvm_arm_setup_shadow_state -- prepare shadow state based on emulated mode
+ * @vcpu: The VCPU pointer
+ */
+void kvm_arm_setup_shadow_state(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
+
+	if (unlikely(vcpu_mode_el2(vcpu))) {
+		flush_shadow_special_regs(vcpu);
+		ctxt->hw_sys_regs = ctxt->shadow_sys_regs;
+	} else {
+		flush_special_regs(vcpu);
+		ctxt->hw_sys_regs = ctxt->sys_regs;
+	}
+}
+
+/**
+ * kvm_arm_restore_shadow_state -- write back shadow state from guest
+ * @vcpu: The VCPU pointer
+ */
+void kvm_arm_restore_shadow_state(struct kvm_vcpu *vcpu)
+{
+	if (unlikely(vcpu_mode_el2(vcpu)))
+		sync_shadow_special_regs(vcpu);
+	else
+		sync_special_regs(vcpu);
+}
+
 void kvm_arm_init_cpu_context(kvm_cpu_context_t *cpu_ctxt)
 {
 	/* This is to set hw_sys_regs of host_cpu_context */
-- 
1.9.1