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, 248 insertions, 0 deletions

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 10ed464..4decdb6 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -15,3 +15,251 @@
  * along with this program; if not, write to the Free Software
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
+
+#include <linux/mman.h>
+#include <linux/kvm_host.h>
+#include <linux/io.h>
+#include <asm/idmap.h>
+#include <asm/pgalloc.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_mmu.h>
+#include <asm/mach/map.h>
+
+extern char  __hyp_idmap_text_start[], __hyp_idmap_text_end[];
+
+static DEFINE_MUTEX(kvm_hyp_pgd_mutex);
+
+static void kvm_set_pte(pte_t *pte, pte_t new_pte)
+{
+	pte_val(*pte) = new_pte;
+	/*
+	 * flush_pmd_entry just takes a void pointer and cleans the necessary
+	 * cache entries, so we can reuse the function for ptes.
+	 */
+	flush_pmd_entry(pte);
+}
+
+static void free_ptes(pmd_t *pmd, unsigned long addr)
+{
+	pte_t *pte;
+	unsigned int i;
+
+	for (i = 0; i < PTRS_PER_PMD; i++, addr += PMD_SIZE) {
+		if (!pmd_none(*pmd) && pmd_table(*pmd)) {
+			pte = pte_offset_kernel(pmd, addr);
+			pte_free_kernel(NULL, pte);
+		}
+		pmd++;
+	}
+}
+
+/**
+ * free_hyp_pmds - free a Hyp-mode level-2 tables and child level-3 tables
+ *
+ * Assumes this is a page table used strictly in Hyp-mode and therefore contains
+ * only mappings in the kernel memory area, which is above PAGE_OFFSET.
+ */
+void free_hyp_pmds(void)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	unsigned long addr;
+
+	mutex_lock(&kvm_hyp_pgd_mutex);
+	for (addr = PAGE_OFFSET; addr != 0; addr += PGDIR_SIZE) {
+		pgd = hyp_pgd + pgd_index(addr);
+		pud = pud_offset(pgd, addr);
+
+		if (pud_none(*pud))
+			continue;
+		BUG_ON(pud_bad(*pud));
+
+		pmd = pmd_offset(pud, addr);
+		free_ptes(pmd, addr);
+		pmd_free(NULL, pmd);
+		pud_clear(pud);
+	}
+	mutex_unlock(&kvm_hyp_pgd_mutex);
+}
+
+static void create_hyp_pte_mappings(pmd_t *pmd, unsigned long start,
+				    unsigned long end)
+{
+	pte_t *pte;
+	unsigned long addr;
+	struct page *page;
+
+	for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
+		pte = pte_offset_kernel(pmd, addr);
+		BUG_ON(!virt_addr_valid(addr));
+		page = virt_to_page(addr);
+		kvm_set_pte(pte, mk_pte(page, PAGE_HYP));
+	}
+}
+
+static void create_hyp_io_pte_mappings(pmd_t *pmd, unsigned long start,
+				       unsigned long end,
+				       unsigned long *pfn_base)
+{
+	pte_t *pte;
+	unsigned long addr;
+
+	for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
+		pte = pte_offset_kernel(pmd, addr);
+		BUG_ON(pfn_valid(*pfn_base));
+		kvm_set_pte(pte, pfn_pte(*pfn_base, PAGE_HYP_DEVICE));
+		(*pfn_base)++;
+	}
+}
+
+static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
+				   unsigned long end, unsigned long *pfn_base)
+{
+	pmd_t *pmd;
+	pte_t *pte;
+	unsigned long addr, next;
+
+	for (addr = start; addr < end; addr = next) {
+		pmd = pmd_offset(pud, addr);
+
+		BUG_ON(pmd_sect(*pmd));
+
+		if (pmd_none(*pmd)) {
+			pte = pte_alloc_one_kernel(NULL, addr);
+			if (!pte) {
+				kvm_err("Cannot allocate Hyp pte\n");
+				return -ENOMEM;
+			}
+			pmd_populate_kernel(NULL, pmd, pte);
+		}
+
+		next = pmd_addr_end(addr, end);
+
+		/*
+		 * If pfn_base is NULL, we map kernel pages into HYP with the
+		 * virtual address. Otherwise, this is considered an I/O
+		 * mapping and we map the physical region starting at
+		 * *pfn_base to [start, end[.
+		 */
+		if (!pfn_base)
+			create_hyp_pte_mappings(pmd, addr, next);
+		else
+			create_hyp_io_pte_mappings(pmd, addr, next, pfn_base);
+	}
+
+	return 0;
+}
+
+static int __create_hyp_mappings(void *from, void *to, unsigned long *pfn_base)
+{
+	unsigned long start = (unsigned long)from;
+	unsigned long end = (unsigned long)to;
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	unsigned long addr, next;
+	int err = 0;
+
+	BUG_ON(start > end);
+	if (start < PAGE_OFFSET)
+		return -EINVAL;
+
+	mutex_lock(&kvm_hyp_pgd_mutex);
+	for (addr = start; addr < end; addr = next) {
+		pgd = hyp_pgd + pgd_index(addr);
+		pud = pud_offset(pgd, addr);
+
+		if (pud_none_or_clear_bad(pud)) {
+			pmd = pmd_alloc_one(NULL, addr);
+			if (!pmd) {
+				kvm_err("Cannot allocate Hyp pmd\n");
+				err = -ENOMEM;
+				goto out;
+			}
+			pud_populate(NULL, pud, pmd);
+		}
+
+		next = pgd_addr_end(addr, end);
+		err = create_hyp_pmd_mappings(pud, addr, next, pfn_base);
+		if (err)
+			goto out;
+	}
+out:
+	mutex_unlock(&kvm_hyp_pgd_mutex);
+	return err;
+}
+
+/**
+ * create_hyp_mappings - map a kernel virtual address range in Hyp mode
+ * @from:	The virtual kernel start address of the range
+ * @to:		The virtual kernel end address of the range (exclusive)
+ *
+ * The same virtual address as the kernel virtual address is also used in
+ * Hyp-mode mapping to the same underlying physical pages.
+ *
+ * Note: Wrapping around zero in the "to" address is not supported.
+ */
+int create_hyp_mappings(void *from, void *to)
+{
+	return __create_hyp_mappings(from, to, NULL);
+}
+
+/**
+ * create_hyp_io_mappings - map a physical IO range in Hyp mode
+ * @from:	The virtual HYP start address of the range
+ * @to:		The virtual HYP end address of the range (exclusive)
+ * @addr:	The physical start address which gets mapped
+ */
+int create_hyp_io_mappings(void *from, void *to, phys_addr_t addr)
+{
+	unsigned long pfn = __phys_to_pfn(addr);
+	return __create_hyp_mappings(from, to, &pfn);
+}
+
+int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	return -EINVAL;
+}
+
+phys_addr_t kvm_mmu_get_httbr(void)
+{
+	VM_BUG_ON(!virt_addr_valid(hyp_pgd));
+	return virt_to_phys(hyp_pgd);
+}
+
+int kvm_mmu_init(void)
+{
+	return hyp_pgd ? 0 : -ENOMEM;
+}
+
+/**
+ * kvm_clear_idmap - remove all idmaps from the hyp pgd
+ *
+ * Free the underlying pmds for all pgds in range and clear the pgds (but
+ * don't free them) afterwards.
+ */
+void kvm_clear_hyp_idmap(void)
+{
+	unsigned long addr, end;
+	unsigned long next;
+	pgd_t *pgd = hyp_pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+
+	addr = virt_to_phys(__hyp_idmap_text_start);
+	end = virt_to_phys(__hyp_idmap_text_end);
+
+	pgd += pgd_index(addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		pud = pud_offset(pgd, addr);
+		pmd = pmd_offset(pud, addr);
+
+		pud_clear(pud);
+		clean_pmd_entry(pmd);
+		pmd_free(NULL, (pmd_t *)((unsigned long)pmd & PAGE_MASK));
+	} while (pgd++, addr = next, addr < end);
+}