[PATCH v3 02/16] KVM: arm64: nv: Implement nested Stage-2 page table walk logic

Marc Zyngier
2024-06-14T14:46:16Z

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

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

Co-developed-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/esr.h | 1 +
arch/arm64/include/asm/kvm_nested.h | 13 ++
arch/arm64/kvm/nested.c | 264 ++++++++++++++++++++++++++++
3 files changed, 278 insertions(+)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 7abf09df7033..15a4be765cad 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -152,6 +152,7 @@
#define ESR_ELx_Xs_MASK (GENMASK_ULL(4, 0))

/* ISS field definitions for exceptions taken in to Hyp */
+#define ESR_ELx_FSC_ADDRSZ (0x00)
#define ESR_ELx_CV (UL(1) << 24)
#define ESR_ELx_COND_SHIFT (20)
#define ESR_ELx_COND_MASK (UL(0xF) << ESR_ELx_COND_SHIFT)
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index a69faee31342..5404b7b843cf 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -68,6 +68,19 @@ extern struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu);
extern void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu);
extern void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu);

+struct kvm_s2_trans {
+ phys_addr_t output;
+ unsigned long block_size;
+ bool writable;
+ bool readable;
+ int level;
+ u32 esr;
+ u64 upper_attr;
+};
+
+extern int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result);
+
int kvm_init_nv_sysregs(struct kvm *kvm);

#ifdef CONFIG_ARM64_PTR_AUTH
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 0a6b894b6390..2fcfaeaeef98 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -91,6 +91,270 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
return 0;
}

+struct s2_walk_info {
+ int (*read_desc)(phys_addr_t pa, u64 *desc, void *data);
+ void *data;
+ u64 baddr;
+ unsigned int max_oa_bits;
+ unsigned int pgshift;
+ unsigned int sl;
+ unsigned int t0sz;
+ bool be;
+};
+
+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 u32 compute_fsc(int level, u32 fsc)
+{
+ return fsc | (level & 0x3);
+}
+
+static int get_ia_size(struct s2_walk_info *wi)
+{
+ return 64 - wi->t0sz;
+}
+
+static int check_base_s2_limits(struct s2_walk_info *wi,
+ int level, int input_size, int stride)
+{
+ int start_size, ia_size;
+
+ ia_size = get_ia_size(wi);
+
+ /* Check translation limits */
+ switch (BIT(wi->pgshift)) {
+ case SZ_64K:
+ if (level == 0 || (level == 1 && ia_size <= 42))
+ return -EFAULT;
+ break;
+ case SZ_16K:
+ if (level == 0 || (level == 1 && ia_size <= 40))
+ return -EFAULT;
+ break;
+ case SZ_4K:
+ if (level < 0 || (level == 0 && ia_size <= 42))
+ return -EFAULT;
+ break;
+ }
+
+ /* Check input size limits */
+ if (input_size > ia_size)
+ 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 s2_walk_info *wi, phys_addr_t output)
+{
+ unsigned int output_size = wi->max_oa_bits;
+
+ 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->srcu read lock held
+ */
+static int walk_nested_s2_pgd(phys_addr_t ipa,
+ struct s2_walk_info *wi, struct kvm_s2_trans *out)
+{
+ 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 (BIT(wi->pgshift)) {
+ default:
+ 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;
+ }
+
+ stride = wi->pgshift - 3;
+ input_size = get_ia_size(wi);
+ if (input_size > 48 || input_size < 25)
+ return -EFAULT;
+
+ ret = check_base_s2_limits(wi, level, input_size, stride);
+ if (WARN_ON(ret))
+ return ret;
+
+ base_lower_bound = 3 + input_size - ((3 - level) * stride +
+ wi->pgshift);
+ base_addr = wi->baddr & GENMASK_ULL(47, base_lower_bound);
+
+ if (check_output_size(wi, base_addr)) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_ADDRSZ);
+ return 1;
+ }
+
+ 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 = wi->read_desc(paddr, &desc, wi->data);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * Handle reversedescriptors if endianness differs between the
+ * host and the guest hypervisor.
+ */
+ if (wi->be)
+ desc = be64_to_cpu((__force __be64)desc);
+ else
+ desc = le64_to_cpu((__force __le64)desc);
+
+ /* Check for valid descriptor at this point */
+ if (!(desc & 1) || ((desc & 3) == 1 && level == 3)) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_FAULT);
+ out->upper_attr = desc;
+ return 1;
+ }
+
+ /* We're at the final level or block translation level */
+ if ((desc & 3) == 1 || level == 3)
+ break;
+
+ if (check_output_size(wi, desc)) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_ADDRSZ);
+ out->upper_attr = desc;
+ return 1;
+ }
+
+ base_addr = desc & GENMASK_ULL(47, wi->pgshift);
+
+ level += 1;
+ addr_top = addr_bottom - 1;
+ }
+
+ if (level < first_block_level) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_FAULT);
+ out->upper_attr = desc;
+ return 1;
+ }
+
+ /*
+ * We don't use the contiguous bit in the stage-2 ptes, so skip check
+ * for misprogramming of the contiguous bit.
+ */
+
+ if (check_output_size(wi, desc)) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_ADDRSZ);
+ out->upper_attr = desc;
+ return 1;
+ }
+
+ if (!(desc & BIT(10))) {
+ out->esr = compute_fsc(level, ESR_ELx_FSC_ACCESS);
+ out->upper_attr = desc;
+ return 1;
+ }
+
+ /* 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);
+ out->readable = desc & (0b01 << 6);
+ out->writable = desc & (0b10 << 6);
+ out->level = level;
+ out->upper_attr = desc & GENMASK_ULL(63, 52);
+ return 0;
+}
+
+static int read_guest_s2_desc(phys_addr_t pa, u64 *desc, void *data)
+{
+ struct kvm_vcpu *vcpu = data;
+
+ return kvm_read_guest(vcpu->kvm, pa, desc, sizeof(*desc));
+}
+
+static void vtcr_to_walk_info(u64 vtcr, 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: /* IMPDEF: treat any other value as 64k */
+ wi->pgshift = 16; break;
+ }
+
+ wi->sl = FIELD_GET(VTCR_EL2_SL0_MASK, vtcr);
+ /* Global limit for now, should eventually be per-VM */
+ wi->max_oa_bits = min(get_kvm_ipa_limit(),
+ ps_to_output_size(FIELD_GET(VTCR_EL2_PS_MASK, vtcr)));
+}
+
+int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
+ struct kvm_s2_trans *result)
+{
+ u64 vtcr = vcpu_read_sys_reg(vcpu, VTCR_EL2);
+ struct s2_walk_info wi;
+ int ret;
+
+ result->esr = 0;
+
+ if (!vcpu_has_nv(vcpu))
+ return 0;
+
+ wi.read_desc = read_guest_s2_desc;
+ wi.data = vcpu;
+ wi.baddr = vcpu_read_sys_reg(vcpu, VTTBR_EL2);
+
+ vtcr_to_walk_info(vtcr, &wi);
+
+ wi.be = vcpu_read_sys_reg(vcpu, SCTLR_EL2) & SCTLR_ELx_EE;
+
+ ret = walk_nested_s2_pgd(gipa, &wi, result);
+ if (ret)
+ result->esr |= (kvm_vcpu_get_esr(vcpu) & ~ESR_ELx_FSC);
+
+ return ret;
+}
+
struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
--
2.39.2