arm64: KVM: use ID map with increased VA range if required

This patch modifies the HYP init code so it can deal with system
RAM residing at an offset which exceeds the reach of VA_BITS.

Like for EL1, this involves configuring an additional level of
translation for the ID map. However, in case of EL2, this implies
that all translations use the extra level, as we cannot seamlessly
switch between translation tables with different numbers of
translation levels.

So add an extra translation table at the root level. Since the
ID map and the runtime HYP map are guaranteed not to overlap, they
can share this root level, and we can essentially merge these two
tables into one.

Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 25 insertions, 2 deletions

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 42a24d6..69c2b4c 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -35,6 +35,7 @@ extern char  __hyp_idmap_text_start[], __hyp_idmap_text_end[];
 
 static pgd_t *boot_hyp_pgd;
 static pgd_t *hyp_pgd;
+static pgd_t *merged_hyp_pgd;
 static DEFINE_MUTEX(kvm_hyp_pgd_mutex);
 
 static unsigned long hyp_idmap_start;
@@ -434,6 +435,11 @@ void free_hyp_pgds(void)
 		free_pages((unsigned long)hyp_pgd, hyp_pgd_order);
 		hyp_pgd = NULL;
 	}
+	if (merged_hyp_pgd) {
+		clear_page(merged_hyp_pgd);
+		free_page((unsigned long)merged_hyp_pgd);
+		merged_hyp_pgd = NULL;
+	}
 
 	mutex_unlock(&kvm_hyp_pgd_mutex);
 }
@@ -1473,12 +1479,18 @@ void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
 
 phys_addr_t kvm_mmu_get_httbr(void)
 {
-	return virt_to_phys(hyp_pgd);
+	if (__kvm_cpu_uses_extended_idmap())
+		return virt_to_phys(merged_hyp_pgd);
+	else
+		return virt_to_phys(hyp_pgd);
 }
 
 phys_addr_t kvm_mmu_get_boot_httbr(void)
 {
-	return virt_to_phys(boot_hyp_pgd);
+	if (__kvm_cpu_uses_extended_idmap())
+		return virt_to_phys(merged_hyp_pgd);
+	else
+		return virt_to_phys(boot_hyp_pgd);
 }
 
 phys_addr_t kvm_get_idmap_vector(void)
@@ -1521,6 +1533,17 @@ int kvm_mmu_init(void)
 		goto out;
 	}
 
+	if (__kvm_cpu_uses_extended_idmap()) {
+		merged_hyp_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+		if (!merged_hyp_pgd) {
+			kvm_err("Failed to allocate extra HYP pgd\n");
+			goto out;
+		}
+		__kvm_extend_hypmap(boot_hyp_pgd, hyp_pgd, merged_hyp_pgd,
+				    hyp_idmap_start);
+		return 0;
+	}
+
 	/* Map the very same page at the trampoline VA */
 	err = 	__create_hyp_mappings(boot_hyp_pgd,
 				      TRAMPOLINE_VA, TRAMPOLINE_VA + PAGE_SIZE,