KVM: arm64: Use LPA2 page-tables for stage2 and hyp stage1

Implement a simple policy whereby if the HW supports FEAT_LPA2 for the
page size we are using, always use LPA2-style page-tables for stage 2
and hyp stage 1 (assuming an nvhe hyp), regardless of the VMM-requested
IPA size or HW-implemented PA size. When in use we can now support up to
52-bit IPA and PA sizes.

We use the previously created cpu feature to track whether LPA2 is
supported for deciding whether to use the LPA2 or classic pte format.

Note that FEAT_LPA2 brings support for bigger block mappings (512GB with
4KB, 64GB with 16KB). We explicitly don't enable these in the library
because stage2_apply_range() works on batch sizes of the largest used
block mapping, and increasing the size of the batch would lead to soft
lockups. See commit 5994bc9e ("KVM: arm64: Limit
stage2_apply_range() batch size to largest block").

With the addition of LPA2 support in the hypervisor, the PA size
supported by the HW must be capped with a runtime decision, rather than
simply using a compile-time decision based on PA_BITS. For example, on a
system that advertises 52 bit PA but does not support FEAT_LPA2, A 4KB
or 16KB kernel compiled with LPA2 support must still limit the PA size
to 48 bits.

Therefore, move the insertion of the PS field into TCR_EL2 out of
__kvm_hyp_init assembly code and instead do it in cpu_prepare_hyp_mode()
where the rest of TCR_EL2 is prepared. This allows us to figure out PS
with kvm_get_parange(), which has the appropriate logic to ensure the
above requirement. (and the PS field of VTCR_EL2 is already populated
this way).
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231127111737.1897081-8-ryan.roberts@arm.com

arch/arm64/include/asm/kvm_pgtable.h

@@ -25,14 +25,24 @@
 #define KVM_PGTABLE_MIN_BLOCK_LEVEL	2U
 #endif
 
-#define kvm_lpa2_is_enabled()		false
+#define kvm_lpa2_is_enabled()		system_supports_lpa2()
+
+static inline u64 kvm_get_parange_max(void)
+{
+	if (kvm_lpa2_is_enabled() ||
+	   (IS_ENABLED(CONFIG_ARM64_PA_BITS_52) && PAGE_SHIFT == 16))
+		return ID_AA64MMFR0_EL1_PARANGE_52;
+	else
+		return ID_AA64MMFR0_EL1_PARANGE_48;
+}
 
 static inline u64 kvm_get_parange(u64 mmfr0)
 {
+	u64 parange_max = kvm_get_parange_max();
 	u64 parange = cpuid_feature_extract_unsigned_field(mmfr0,
 				ID_AA64MMFR0_EL1_PARANGE_SHIFT);
-	if (parange > ID_AA64MMFR0_EL1_PARANGE_MAX)
-		parange = ID_AA64MMFR0_EL1_PARANGE_MAX;
+	if (parange > parange_max)
+		parange = parange_max;
 
 	return parange;
 }
@@ -43,6 +53,8 @@ typedef u64 kvm_pte_t;
 
 #define KVM_PTE_ADDR_MASK		GENMASK(47, PAGE_SHIFT)
 #define KVM_PTE_ADDR_51_48		GENMASK(15, 12)
+#define KVM_PTE_ADDR_MASK_LPA2		GENMASK(49, PAGE_SHIFT)
+#define KVM_PTE_ADDR_51_50_LPA2		GENMASK(9, 8)
 
 #define KVM_PHYS_INVALID		(-1ULL)
 
@@ -53,21 +65,34 @@ static inline bool kvm_pte_valid(kvm_pte_t pte)
 
 static inline u64 kvm_pte_to_phys(kvm_pte_t pte)
 {
-	u64 pa = pte & KVM_PTE_ADDR_MASK;
-
-	if (PAGE_SHIFT == 16)
-		pa |= FIELD_GET(KVM_PTE_ADDR_51_48, pte) << 48;
+	u64 pa;
+
+	if (kvm_lpa2_is_enabled()) {
+		pa = pte & KVM_PTE_ADDR_MASK_LPA2;
+		pa |= FIELD_GET(KVM_PTE_ADDR_51_50_LPA2, pte) << 50;
+	} else {
+		pa = pte & KVM_PTE_ADDR_MASK;
+		if (PAGE_SHIFT == 16)
+			pa |= FIELD_GET(KVM_PTE_ADDR_51_48, pte) << 48;
+	}
 
 	return pa;
 }
 
 static inline kvm_pte_t kvm_phys_to_pte(u64 pa)
 {
-	kvm_pte_t pte = pa & KVM_PTE_ADDR_MASK;
-
-	if (PAGE_SHIFT == 16) {
-		pa &= GENMASK(51, 48);
-		pte |= FIELD_PREP(KVM_PTE_ADDR_51_48, pa >> 48);
+	kvm_pte_t pte;
+
+	if (kvm_lpa2_is_enabled()) {
+		pte = pa & KVM_PTE_ADDR_MASK_LPA2;
+		pa &= GENMASK(51, 50);
+		pte |= FIELD_PREP(KVM_PTE_ADDR_51_50_LPA2, pa >> 50);
+	} else {
+		pte = pa & KVM_PTE_ADDR_MASK;
+		if (PAGE_SHIFT == 16) {
+			pa &= GENMASK(51, 48);
+			pte |= FIELD_PREP(KVM_PTE_ADDR_51_48, pa >> 48);
+		}
 	}
 
 	return pte;

arch/arm64/kvm/arm.c

@@ -1837,6 +1837,7 @@ static int kvm_init_vector_slots(void)
 static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
 {
 	struct kvm_nvhe_init_params *params = per_cpu_ptr_nvhe_sym(kvm_init_params, cpu);
+	u64 mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
 	unsigned long tcr;
 
 	/*
@@ -1859,6 +1860,10 @@ static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
 	}
 	tcr &= ~TCR_T0SZ_MASK;
 	tcr |= TCR_T0SZ(hyp_va_bits);
+	tcr &= ~TCR_EL2_PS_MASK;
+	tcr |= FIELD_PREP(TCR_EL2_PS_MASK, kvm_get_parange(mmfr0));
+	if (kvm_lpa2_is_enabled())
+		tcr |= TCR_EL2_DS;
 	params->tcr_el2 = tcr;
 
 	params->pgd_pa = kvm_mmu_get_httbr();

arch/arm64/kvm/hyp/nvhe/hyp-init.S

@@ -122,11 +122,7 @@ alternative_if ARM64_HAS_CNP
 alternative_else_nop_endif
 	msr	ttbr0_el2, x2
 
-	/*
-	 * Set the PS bits in TCR_EL2.
-	 */
 	ldr	x0, [x0, #NVHE_INIT_TCR_EL2]
-	tcr_compute_pa_size x0, #TCR_EL2_PS_SHIFT, x1, x2
 	msr	tcr_el2, x0
 
 	isb

arch/arm64/kvm/hyp/pgtable.c

@@ -79,7 +79,10 @@ static bool kvm_pgtable_walk_skip_cmo(const struct kvm_pgtable_visit_ctx *ctx)
 
 static bool kvm_phys_is_valid(u64 phys)
 {
-	return phys < BIT(id_aa64mmfr0_parange_to_phys_shift(ID_AA64MMFR0_EL1_PARANGE_MAX));
+	u64 parange_max = kvm_get_parange_max();
+	u8 shift = id_aa64mmfr0_parange_to_phys_shift(parange_max);
+
+	return phys < BIT(shift);
 }
 
 static bool kvm_block_mapping_supported(const struct kvm_pgtable_visit_ctx *ctx, u64 phys)
@@ -408,7 +411,8 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
 	}
 
 	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_AP, ap);
-	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_SH, sh);
+	if (!kvm_lpa2_is_enabled())
+		attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_SH, sh);
 	attr |= KVM_PTE_LEAF_ATTR_LO_S1_AF;
 	attr |= prot & KVM_PTE_LEAF_ATTR_HI_SW;
 	*ptep = attr;
@@ -654,6 +658,9 @@ u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift)
 		vtcr |= VTCR_EL2_HA;
 #endif /* CONFIG_ARM64_HW_AFDBM */
 
+	if (kvm_lpa2_is_enabled())
+		vtcr |= VTCR_EL2_DS;
+
 	/* Set the vmid bits */
 	vtcr |= (get_vmid_bits(mmfr1) == 16) ?
 		VTCR_EL2_VS_16BIT :
@@ -711,7 +718,9 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
 	if (prot & KVM_PGTABLE_PROT_W)
 		attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
 
-	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);
+	if (!kvm_lpa2_is_enabled())
+		attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);
+
 	attr |= KVM_PTE_LEAF_ATTR_LO_S2_AF;
 	attr |= prot & KVM_PTE_LEAF_ATTR_HI_SW;
 	*ptep = attr;