[PATCH v2 22/36] KVM: arm64: Prepare to handle traps on deferred VM sysregs

[Christoffer Dall]

When we defer the save/restore of system registers to vcpu_load and
vcpu_put, we need to take care of the emulation code that handles traps
to these registers, since simply reading the memory array will return
stale data.

Therefore, introduce two functions to directly read/write the registers
from the physical CPU when we're on a VHE system that has loaded the
system registers onto the physical CPU.

Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---

Notes:
    Changes since v1:
     - Removed spurious white space

 arch/arm64/include/asm/kvm_host.h |  4 +++
 arch/arm64/kvm/sys_regs.c         | 53 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index de0d55b30b61..f6afe685a280 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -279,6 +279,10 @@ struct kvm_vcpu_arch {
 
 	/* Detect first run of a vcpu */
 	bool has_run_once;
+
+	/* True when deferrable sysregs are loaded on the physical CPU,
+	 * see kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs. */
+	bool sysregs_loaded_on_cpu;
 };
 
 #define vcpu_gp_regs(v)		(&(v)->arch.ctxt.gp_regs)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 62c12ab9e6c4..80adbec933de 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -35,6 +35,7 @@
 #include <asm/kvm_coproc.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_host.h>
+#include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 #include <asm/perf_event.h>
 #include <asm/sysreg.h>
@@ -111,6 +112,54 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 	return true;
 }
 
+static u64 read_deferrable_vm_reg(struct kvm_vcpu *vcpu, int reg)
+{
+	if (vcpu->arch.sysregs_loaded_on_cpu) {
+		switch (reg) {
+		case SCTLR_EL1:		return read_sysreg_el1(sctlr);
+		case TTBR0_EL1:		return read_sysreg_el1(ttbr0);
+		case TTBR1_EL1:		return read_sysreg_el1(ttbr1);
+		case TCR_EL1:		return read_sysreg_el1(tcr);
+		case ESR_EL1:		return read_sysreg_el1(esr);
+		case FAR_EL1:		return read_sysreg_el1(far);
+		case AFSR0_EL1:		return read_sysreg_el1(afsr0);
+		case AFSR1_EL1:		return read_sysreg_el1(afsr1);
+		case MAIR_EL1:		return read_sysreg_el1(mair);
+		case AMAIR_EL1:		return read_sysreg_el1(amair);
+		case CONTEXTIDR_EL1:	return read_sysreg_el1(contextidr);
+		case DACR32_EL2:	return read_sysreg(dacr32_el2);
+		case IFSR32_EL2:	return read_sysreg(ifsr32_el2);
+		default:		BUG();
+		}
+	}
+
+	return vcpu_sys_reg(vcpu, reg);
+}
+
+static void write_deferrable_vm_reg(struct kvm_vcpu *vcpu, int reg, u64 val)
+{
+	if (vcpu->arch.sysregs_loaded_on_cpu) {
+		switch (reg) {
+		case SCTLR_EL1:		write_sysreg_el1(val, sctlr);	return;
+		case TTBR0_EL1:		write_sysreg_el1(val, ttbr0);	return;
+		case TTBR1_EL1:		write_sysreg_el1(val, ttbr1);	return;
+		case TCR_EL1:		write_sysreg_el1(val, tcr);	return;
+		case ESR_EL1:		write_sysreg_el1(val, esr);	return;
+		case FAR_EL1:		write_sysreg_el1(val, far);	return;
+		case AFSR0_EL1:		write_sysreg_el1(val, afsr0);	return;
+		case AFSR1_EL1:		write_sysreg_el1(val, afsr1);	return;
+		case MAIR_EL1:		write_sysreg_el1(val, mair);	return;
+		case AMAIR_EL1:		write_sysreg_el1(val, amair);	return;
+		case CONTEXTIDR_EL1:	write_sysreg_el1(val, contextidr); return;
+		case DACR32_EL2:	write_sysreg(val, dacr32_el2); return;
+		case IFSR32_EL2:	write_sysreg(val, ifsr32_el2); return;
+		default:		BUG();
+		}
+	}
+
+	vcpu_sys_reg(vcpu, reg) = val;
+}
+
 /*
  * Generic accessor for VM registers. Only called as long as HCR_TVM
  * is set. If the guest enables the MMU, we stop trapping the VM
@@ -133,14 +182,14 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
 	if (!p->is_aarch32 || !p->is_32bit) {
 		val = p->regval;
 	} else {
-		val = vcpu_sys_reg(vcpu, reg);
+		val = read_deferrable_vm_reg(vcpu, reg);
 		if (r->reg % 2)
 			val = (p->regval << 32) | (u64)lower_32_bits(val);
 		else
 			val = ((u64)upper_32_bits(val) << 32) |
 				(u64)lower_32_bits(p->regval);
 	}
-	vcpu_sys_reg(vcpu, reg) = val;
+	write_deferrable_vm_reg(vcpu, reg, val);
 
 	kvm_toggle_cache(vcpu, was_enabled);
 	return true;
-- 
2.14.2