arm64: kvm: allows kvm cpu hotplug

The current kvm implementation on arm64 does cpu-specific initialization
at system boot, and has no way to gracefully shutdown a core in terms of
kvm. This prevents kexec from rebooting the system at EL2.

This patch adds a cpu tear-down function and also puts an existing cpu-init
code into a separate function, kvm_arch_hardware_disable() and
kvm_arch_hardware_enable() respectively.
We don't need the arm64 specific cpu hotplug hook any more.

Since this patch modifies common code between arm and arm64, one stub
definition, __cpu_reset_hyp_mode(), is added on arm side to avoid
compilation errors.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[Rebase, added separate VHE init/exit path, changed resets use of
 kvm_call_hyp() to the __version, en/disabled hardware in init_subsystems(),
 added icache maintenance to __kvm_hyp_reset() and removed lr restore, removed
 guest-enter after teardown handling]
Signed-off-by: James Morse <james.morse@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

2 files changed, 52 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 5ce1b47ef770..44ec4cb23ae7 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -139,6 +139,44 @@ merged:
         eret
 ENDPROC(__kvm_hyp_init)
 
+        /*
+         * x0: HYP boot pgd
+         * x1: HYP phys_idmap_start
+         */
+ENTRY(__kvm_hyp_reset)
+        /* We're in trampoline code in VA, switch back to boot page tables */
+        msr     ttbr0_el2, x0
+        isb
+
+        /* Ensure the PA branch doesn't find a stale tlb entry or stale code. */
+        ic      iallu
+        tlbi    alle2
+        dsb     sy
+        isb
+
+        /* Branch into PA space */
+        adr     x0, 1f
+        bfi     x1, x0, #0, #PAGE_SHIFT
+        br      x1
+
+        /* We're now in idmap, disable MMU */
+1:      mrs     x0, sctlr_el2
+        ldr     x1, =SCTLR_ELx_FLAGS
+        bic     x0, x0, x1              // Clear SCTL_M and etc
+        msr     sctlr_el2, x0
+        isb
+
+        /* Invalidate the old TLBs */
+        tlbi    alle2
+        dsb     sy
+
+        /* Install stub vectors */
+        adr_l   x0, __hyp_stub_vectors
+        msr     vbar_el2, x0
+
+        eret
+ENDPROC(__kvm_hyp_reset)
+
         .ltorg
 
         .popsection
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 9677bf069bcc..4062e6dd4cc1 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -29,7 +29,9 @@
 #include <asm/cputype.h>
 #include <asm/ptrace.h>
 #include <asm/kvm_arm.h>
+#include <asm/kvm_asm.h>
 #include <asm/kvm_coproc.h>
+#include <asm/kvm_mmu.h>
 
 /*
  * ARMv8 Reset Values
@@ -130,3 +132,15 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
         /* Reset timer */
         return kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
 }
+
+extern char __hyp_idmap_text_start[];
+
+phys_addr_t kvm_hyp_reset_entry(void)
+{
+        unsigned long offset;
+
+        offset = (unsigned long)__kvm_hyp_reset
+                 - ((unsigned long)__hyp_idmap_text_start & PAGE_MASK);
+
+        return TRAMPOLINE_VA + offset;
+}