KVM: ARM: Hypervisor initialization

Sets up KVM code to handle all exceptions taken to Hyp mode.

When the kernel is booted in Hyp mode, calling an hvc instruction with r0
pointing to the new vectors, the HVBAR is changed to the the vector pointers.
This allows subsystems (like KVM here) to execute code in Hyp-mode with the
MMU disabled.

We initialize other Hyp-mode registers and enables the MMU for Hyp-mode from
the id-mapped hyp initialization code. Afterwards, the HVBAR is changed to
point to KVM Hyp vectors used to catch guest faults and to switch to Hyp mode
to perform a world-switch into a KVM guest.

Also provides memory mapping code to map required code pages, data structures,
and I/O regions  accessed in Hyp mode at the same virtual address as the host
kernel virtual addresses, but which conforms to the architectural requirements
for translations in Hyp mode. This interface is added in arch/arm/kvm/arm_mmu.c
and comprises:
 - create_hyp_mappings(from, to);
 - create_hyp_io_mappings(from, to, phys_addr);
 - free_hyp_pmds();

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 172 insertions, 0 deletions

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d3506b4001aa..2c6b780e78a7 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -34,11 +34,21 @@
 #include <asm/ptrace.h>
 #include <asm/mman.h>
 #include <asm/cputype.h>
+#include <asm/tlbflush.h>
+#include <asm/virt.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_asm.h>
+#include <asm/kvm_mmu.h>
 
 #ifdef REQUIRES_VIRT
 __asm__(".arch_extension        virt");
 #endif
 
+static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
+static struct vfp_hard_struct __percpu *kvm_host_vfp_state;
+static unsigned long hyp_default_vectors;
+
+
 int kvm_arch_hardware_enable(void *garbage)
 {
         return 0;
@@ -331,9 +341,171 @@ long kvm_arch_vm_ioctl(struct file *filp,
         return -EINVAL;
 }
 
+static void cpu_init_hyp_mode(void *vector)
+{
+        unsigned long long pgd_ptr;
+        unsigned long pgd_low, pgd_high;
+        unsigned long hyp_stack_ptr;
+        unsigned long stack_page;
+        unsigned long vector_ptr;
+
+        /* Switch from the HYP stub to our own HYP init vector */
+        __hyp_set_vectors((unsigned long)vector);
+
+        pgd_ptr = (unsigned long long)kvm_mmu_get_httbr();
+        pgd_low = (pgd_ptr & ((1ULL << 32) - 1));
+        pgd_high = (pgd_ptr >> 32ULL);
+        stack_page = __get_cpu_var(kvm_arm_hyp_stack_page);
+        hyp_stack_ptr = stack_page + PAGE_SIZE;
+        vector_ptr = (unsigned long)__kvm_hyp_vector;
+
+        /*
+         * Call initialization code, and switch to the full blown
+         * HYP code. The init code doesn't need to preserve these registers as
+         * r1-r3 and r12 are already callee save according to the AAPCS.
+         * Note that we slightly misuse the prototype by casing the pgd_low to
+         * a void *.
+         */
+        kvm_call_hyp((void *)pgd_low, pgd_high, hyp_stack_ptr, vector_ptr);
+}
+
+/**
+ * Inits Hyp-mode on all online CPUs
+ */
+static int init_hyp_mode(void)
+{
+        phys_addr_t init_phys_addr;
+        int cpu;
+        int err = 0;
+
+        /*
+         * Allocate Hyp PGD and setup Hyp identity mapping
+         */
+        err = kvm_mmu_init();
+        if (err)
+                goto out_err;
+
+        /*
+         * It is probably enough to obtain the default on one
+         * CPU. It's unlikely to be different on the others.
+         */
+        hyp_default_vectors = __hyp_get_vectors();
+
+        /*
+         * Allocate stack pages for Hypervisor-mode
+         */
+        for_each_possible_cpu(cpu) {
+                unsigned long stack_page;
+
+                stack_page = __get_free_page(GFP_KERNEL);
+                if (!stack_page) {
+                        err = -ENOMEM;
+                        goto out_free_stack_pages;
+                }
+
+                per_cpu(kvm_arm_hyp_stack_page, cpu) = stack_page;
+        }
+
+        /*
+         * Execute the init code on each CPU.
+         *
+         * Note: The stack is not mapped yet, so don't do anything else than
+         * initializing the hypervisor mode on each CPU using a local stack
+         * space for temporary storage.
+         */
+        init_phys_addr = virt_to_phys(__kvm_hyp_init);
+        for_each_online_cpu(cpu) {
+                smp_call_function_single(cpu, cpu_init_hyp_mode,
+                                         (void *)(long)init_phys_addr, 1);
+        }
+
+        /*
+         * Unmap the identity mapping
+         */
+        kvm_clear_hyp_idmap();
+
+        /*
+         * Map the Hyp-code called directly from the host
+         */
+        err = create_hyp_mappings(__kvm_hyp_code_start, __kvm_hyp_code_end);
+        if (err) {
+                kvm_err("Cannot map world-switch code\n");
+                goto out_free_mappings;
+        }
+
+        /*
+         * Map the Hyp stack pages
+         */
+        for_each_possible_cpu(cpu) {
+                char *stack_page = (char *)per_cpu(kvm_arm_hyp_stack_page, cpu);
+                err = create_hyp_mappings(stack_page, stack_page + PAGE_SIZE);
+
+                if (err) {
+                        kvm_err("Cannot map hyp stack\n");
+                        goto out_free_mappings;
+                }
+        }
+
+        /*
+         * Map the host VFP structures
+         */
+        kvm_host_vfp_state = alloc_percpu(struct vfp_hard_struct);
+        if (!kvm_host_vfp_state) {
+                err = -ENOMEM;
+                kvm_err("Cannot allocate host VFP state\n");
+                goto out_free_mappings;
+        }
+
+        for_each_possible_cpu(cpu) {
+                struct vfp_hard_struct *vfp;
+
+                vfp = per_cpu_ptr(kvm_host_vfp_state, cpu);
+                err = create_hyp_mappings(vfp, vfp + 1);
+
+                if (err) {
+                        kvm_err("Cannot map host VFP state: %d\n", err);
+                        goto out_free_vfp;
+                }
+        }
+
+        kvm_info("Hyp mode initialized successfully\n");
+        return 0;
+out_free_vfp:
+        free_percpu(kvm_host_vfp_state);
+out_free_mappings:
+        free_hyp_pmds();
+out_free_stack_pages:
+        for_each_possible_cpu(cpu)
+                free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
+out_err:
+        kvm_err("error initializing Hyp mode: %d\n", err);
+        return err;
+}
+
+/**
+ * Initialize Hyp-mode and memory mappings on all CPUs.
+ */
 int kvm_arch_init(void *opaque)
 {
+        int err;
+
+        if (!is_hyp_mode_available()) {
+                kvm_err("HYP mode not available\n");
+                return -ENODEV;
+        }
+
+        if (kvm_target_cpu() < 0) {
+                kvm_err("Target CPU not supported!\n");
+                return -ENODEV;
+        }
+
+        err = init_hyp_mode();
+        if (err)
+                goto out_err;
+
         return 0;
+out_err:
+        return err;
 }
 
 /* NOP: Compiling as a module not supported */