linux-kernel - [PATCH v3 56/60] arm64: kvm: Limit HYP VA and host S2 range to 48 bits when LPA2 is in effect

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Message-Id: <20230307140522.2311461-57-ardb@kernel.org>
Date:   Tue,  7 Mar 2023 15:05:18 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ryan Roberts <ryan.roberts@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH v3 56/60] arm64: kvm: Limit HYP VA and host S2 range to 48 bits when LPA2 is in effect

The KVM code needs more work to support 5 level paging with LPA2, so for
the time being, limit KVM to 48 bit addressing on 4k and 16k pagesize
configurations. This can be reverted once the LPA2 support for KVM is
merged.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 2 ++
 arch/arm64/kvm/mmu.c                  | 5 ++++-
 arch/arm64/kvm/va_layout.c            | 9 +++++----
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 552653fa18be34b2..e00b87ed4a8400f6 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -128,6 +128,8 @@ static void prepare_host_vtcr(void)
 	/* The host stage 2 is id-mapped, so use parange for T0SZ */
 	parange = kvm_get_parange(id_aa64mmfr0_el1_sys_val);
 	phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
+	if (IS_ENABLED(CONFIG_ARM64_LPA2) && phys_shift > 48)
+		phys_shift = 48; // not implemented yet
 
 	host_mmu.arch.vtcr = kvm_get_vtcr(id_aa64mmfr0_el1_sys_val,
 					  id_aa64mmfr1_el1_sys_val, phys_shift);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 4e7c0f9a9c286c09..2ad9e6f1e101e52d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -661,7 +661,8 @@ static int get_user_mapping_size(struct kvm *kvm, u64 addr)
 {
 	struct kvm_pgtable pgt = {
 		.pgd		= (kvm_pteref_t)kvm->mm->pgd,
-		.ia_bits	= vabits_actual,
+		.ia_bits	= IS_ENABLED(CONFIG_ARM64_LPA2) ? 48
+								: vabits_actual,
 		.start_level	= (KVM_PGTABLE_MAX_LEVELS -
 				   ARM64_HW_PGTABLE_LEVELS(pgt.ia_bits)),
 		.mm_ops		= &kvm_user_mm_ops,
@@ -1703,6 +1704,8 @@ int __init kvm_mmu_init(u32 *hyp_va_bits)
 	idmap_bits = 48;
 	kernel_bits = vabits_actual;
 	*hyp_va_bits = max(idmap_bits, kernel_bits);
+	if (IS_ENABLED(CONFIG_ARM64_LPA2))
+		*hyp_va_bits = 48; // LPA2 is not yet supported in KVM
 
 	kvm_debug("Using %u-bit virtual addresses at EL2\n", *hyp_va_bits);
 	kvm_debug("IDMAP page: %lx\n", hyp_idmap_start);
diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index 341b67e2f2514e55..ac87d0c39c38f7d9 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -59,12 +59,13 @@ static void init_hyp_physvirt_offset(void)
  */
 __init void kvm_compute_layout(void)
 {
+	u64 vabits = IS_ENABLED(CONFIG_ARM64_LPA2) ? 48 : vabits_actual; // not yet
 	phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
 	u64 hyp_va_msb;
 
 	/* Where is my RAM region? */
-	hyp_va_msb  = idmap_addr & BIT(vabits_actual - 1);
-	hyp_va_msb ^= BIT(vabits_actual - 1);
+	hyp_va_msb  = idmap_addr & BIT(vabits - 1);
+	hyp_va_msb ^= BIT(vabits - 1);
 
 	tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
 			(u64)(high_memory - 1));
@@ -72,10 +73,10 @@ __init void kvm_compute_layout(void)
 	va_mask = GENMASK_ULL(tag_lsb - 1, 0);
 	tag_val = hyp_va_msb;
 
-	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && tag_lsb != (vabits_actual - 1) &&
+	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && tag_lsb != (vabits - 1) &&
 	    !kaslr_disabled_cmdline()) {
 		/* We have some free bits to insert a random tag. */
-		tag_val |= get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);
+		tag_val |= get_random_long() & GENMASK_ULL(vabits - 2, tag_lsb);
 	}
 	tag_val >>= tag_lsb;
 
-- 
2.39.2