[RFC 42/55] KVM: arm64: Implement nested Stage-2 page table walk logic

Jintack Lim
2017-01-09T06:24:38Z

From: Christoffer Dall <christoffer.dall@linaro.org>

Based on the pseudo-code in the ARM ARM, implement a stage 2 software
page table walker.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
---
arch/arm/include/asm/kvm_mmu.h | 11 ++
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/include/asm/kvm_mmu.h | 13 +++
arch/arm64/kvm/mmu-nested.c | 223 +++++++++++++++++++++++++++++++++++++++
4 files changed, 248 insertions(+)

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index ae3aa39..ab41a10 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -230,6 +230,17 @@ static inline unsigned int kvm_get_vmid_bits(void)
return 8;
}

+struct kvm_s2_trans {
+ phys_addr_t output;
+ phys_addr_t block_size;
+};
+
+static inline int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result)
+{
+ return 0;
+}
+
static inline void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu) { }
static inline int kvm_nested_s2_init(struct kvm_vcpu *vcpu) { return 0; }
static inline void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu) { }
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index feded61..f9addf3 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -103,6 +103,7 @@
#define VTCR_EL2_RES1 (1 << 31)
#define VTCR_EL2_HD (1 << 22)
#define VTCR_EL2_HA (1 << 21)
+#define VTCR_EL2_PS_SHIFT TCR_EL2_PS_SHIFT
#define VTCR_EL2_PS_MASK TCR_EL2_PS_MASK
#define VTCR_EL2_TG0_MASK TCR_TG0_MASK
#define VTCR_EL2_TG0_4K TCR_TG0_4K
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index e4d5d54..bf94f0c 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -324,10 +324,17 @@ static inline unsigned int kvm_get_vmid_bits(void)
return (cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR1_VMIDBITS_SHIFT) == 2) ? 16 : 8;
}

+struct kvm_s2_trans {
+ phys_addr_t output;
+ phys_addr_t block_size;
+};
+
#ifdef CONFIG_KVM_ARM_NESTED_HYP
struct kvm_nested_s2_mmu *get_nested_mmu(struct kvm_vcpu *vcpu, u64 vttbr);
struct kvm_s2_mmu *vcpu_get_active_s2_mmu(struct kvm_vcpu *vcpu);
bool handle_vttbr_update(struct kvm_vcpu *vcpu, u64 vttbr);
+int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result);
void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu);
int kvm_nested_s2_init(struct kvm_vcpu *vcpu);
void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu);
@@ -350,6 +357,12 @@ static inline bool handle_vttbr_update(struct kvm_vcpu *vcpu, u64 vttbr)
return false;
}

+static inline int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result)
+{
+ return 0;
+}
+
static inline void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu) { }
static inline int kvm_nested_s2_init(struct kvm_vcpu *vcpu) { return 0; }
static inline void kvm_nested_s2_teardown(struct kvm_vcpu *vcpu) { }
diff --git a/arch/arm64/kvm/mmu-nested.c b/arch/arm64/kvm/mmu-nested.c
index b22b78c..a2fab41 100644
--- a/arch/arm64/kvm/mmu-nested.c
+++ b/arch/arm64/kvm/mmu-nested.c
@@ -23,6 +23,229 @@
#include <asm/kvm_mmu.h>
#include <asm/kvm_nested.h>

+struct s2_walk_info {
+ unsigned int pgshift;
+ unsigned int pgsize;
+ unsigned int ps;
+ unsigned int sl;
+ unsigned int t0sz;
+};
+
+static unsigned int ps_to_output_size(unsigned int ps)
+{
+ switch (ps) {
+ case 0: return 32;
+ case 1: return 36;
+ case 2: return 40;
+ case 3: return 42;
+ case 4: return 44;
+ case 5:
+ default:
+ return 48;
+ }
+}
+
+static unsigned int pa_max(void)
+{
+ u64 parange = read_sysreg(id_aa64mmfr0_el1) & 7;
+
+ return ps_to_output_size(parange);
+}
+
+static int vcpu_inject_s2_trans_fault(struct kvm_vcpu *vcpu, gpa_t ipa,
+ int level)
+{
+ /* TODO: Implement */
+ return -EFAULT;
+}
+
+static int vcpu_inject_s2_addr_sz_fault(struct kvm_vcpu *vcpu, gpa_t ipa,
+ int level)
+{
+ /* TODO: Implement */
+ return -EFAULT;
+}
+
+static int vcpu_inject_s2_access_flag_fault(struct kvm_vcpu *vcpu, gpa_t ipa,
+ int level)
+{
+ /* TODO: Implement */
+ return -EFAULT;
+}
+
+static int check_base_s2_limits(struct kvm_vcpu *vcpu, struct s2_walk_info *wi,
+ int level, int input_size, int stride)
+{
+ int start_size;
+
+ /* Check translation limits */
+ switch (wi->pgsize) {
+ case SZ_64K:
+ if (level == 0 || (level == 1 && pa_max() <= 42))
+ return -EFAULT;
+ break;
+ case SZ_16K:
+ if (level == 0 || (level == 1 && pa_max() <= 40))
+ return -EFAULT;
+ break;
+ case SZ_4K:
+ if (level < 0 || (level == 0 && pa_max() <= 42))
+ return -EFAULT;
+ break;
+ }
+
+ /* Check input size limits */
+ if (input_size > pa_max() &&
+ (!vcpu_mode_is_32bit(vcpu) || input_size > 40))
+ return -EFAULT;
+
+ /* Check number of entries in starting level table */
+ start_size = input_size - ((3 - level) * stride + wi->pgshift);
+ if (start_size < 1 || start_size > stride + 4)
+ return -EFAULT;
+
+ return 0;
+}
+
+/* Check if output is within boundaries */
+static int check_output_size(struct kvm_vcpu *vcpu, struct s2_walk_info *wi,
+ phys_addr_t output)
+{
+ unsigned int output_size = ps_to_output_size(wi->ps);
+
+ if (output_size > pa_max())
+ output_size = pa_max();
+
+ if (output_size != 48 && (output & GENMASK_ULL(47, output_size)))
+ return -1;
+
+ return 0;
+}
+
+/*
+ * This is essentially a C-version of the pseudo code from the ARM ARM
+ * AArch64.TranslationTableWalk function. I strongly recommend looking at
+ * that pseudocode in trying to understand this.
+ *
+ * Must be called with the kvm->srcy read lock held
+ */
+static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, phys_addr_t ipa,
+ struct s2_walk_info *wi, struct kvm_s2_trans *out)
+{
+ u64 vttbr = vcpu->arch.ctxt.el2_regs[VTTBR_EL2];
+ int first_block_level, level, stride, input_size, base_lower_bound;
+ phys_addr_t base_addr;
+ unsigned int addr_top, addr_bottom;
+ u64 desc; /* page table entry */
+ int ret;
+ phys_addr_t paddr;
+
+ switch (wi->pgsize) {
+ case SZ_64K:
+ case SZ_16K:
+ level = 3 - wi->sl;
+ first_block_level = 2;
+ break;
+ case SZ_4K:
+ level = 2 - wi->sl;
+ first_block_level = 1;
+ break;
+ default:
+ /* GCC is braindead */
+ WARN(1, "Page size is none of 4K, 16K or 64K");
+ }
+
+ stride = wi->pgshift - 3;
+ input_size = 64 - wi->t0sz;
+ if (input_size > 48 || input_size < 25)
+ return -EFAULT;
+
+ ret = check_base_s2_limits(vcpu, wi, level, input_size, stride);
+ if (WARN_ON(ret))
+ return ret;
+
+ if (check_output_size(vcpu, wi, vttbr))
+ return vcpu_inject_s2_addr_sz_fault(vcpu, ipa, level);
+
+ base_lower_bound = 3 + input_size - ((3 - level) * stride +
+ wi->pgshift);
+ base_addr = vttbr & GENMASK_ULL(47, base_lower_bound);
+
+ addr_top = input_size - 1;
+
+ while (1) {
+ phys_addr_t index;
+
+ addr_bottom = (3 - level) * stride + wi->pgshift;
+ index = (ipa & GENMASK_ULL(addr_top, addr_bottom))
+ >> (addr_bottom - 3);
+
+ paddr = base_addr | index;
+ ret = kvm_read_guest(vcpu->kvm, paddr, &desc, sizeof(desc));
+ if (ret < 0)
+ return ret;
+
+ /* Check for valid descriptor at this point */
+ if (!(desc & 1) || ((desc & 3) == 1 && level == 3))
+ return vcpu_inject_s2_trans_fault(vcpu, ipa, level);
+
+ /* We're@the final level or block translation level */
+ if ((desc & 3) == 1 || level == 3)
+ break;
+
+ if (check_output_size(vcpu, wi, desc))
+ return vcpu_inject_s2_addr_sz_fault(vcpu, ipa, level);
+
+ base_addr = desc & GENMASK_ULL(47, wi->pgshift);
+
+ level += 1;
+ addr_top = addr_bottom - 1;
+ }
+
+ if (level < first_block_level)
+ return vcpu_inject_s2_trans_fault(vcpu, ipa, level);
+
+ /* TODO: Consider checking contiguous bit setting */
+
+ if (check_output_size(vcpu, wi, desc))
+ return vcpu_inject_s2_addr_sz_fault(vcpu, ipa, level);
+
+ if (!(desc & BIT(10)))
+ return vcpu_inject_s2_access_flag_fault(vcpu, ipa, level);
+
+ /* Calculate and return the result */
+ paddr = (desc & GENMASK_ULL(47, addr_bottom)) |
+ (ipa & GENMASK_ULL(addr_bottom - 1, 0));
+ out->output = paddr;
+ out->block_size = 1UL << ((3 - level) * stride + wi->pgshift);
+ return 0;
+}
+
+int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result)
+{
+ u64 vtcr = vcpu->arch.ctxt.el2_regs[VTCR_EL2];
+ struct s2_walk_info wi;
+
+ wi.t0sz = vtcr & TCR_EL2_T0SZ_MASK;
+
+ switch (vtcr & VTCR_EL2_TG0_MASK) {
+ case VTCR_EL2_TG0_4K:
+ wi.pgshift = 12; break;
+ case VTCR_EL2_TG0_16K:
+ wi.pgshift = 14; break;
+ case VTCR_EL2_TG0_64K:
+ default:
+ wi.pgshift = 16; break;
+ }
+ wi.pgsize = 1UL << wi.pgshift;
+ wi.ps = (vtcr & VTCR_EL2_PS_MASK) >> VTCR_EL2_PS_SHIFT;
+ wi.sl = (vtcr & VTCR_EL2_SL0_MASK) >> VTCR_EL2_SL0_SHIFT;
+
+ /* TODO: Reversedescriptor if SCTLR_EL2.EE == 1 */
+
+ return walk_nested_s2_pgd(vcpu, gipa, &wi, result);
+}

/* expects kvm->mmu_lock to be held */
void kvm_nested_s2_all_vcpus_wp(struct kvm *kvm)
--
1.9.1