linux-kernel - [PATCH 1/1] KVM: arm64: Fix hyp VA size between layout and MMU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251223193440.1441657-2-pekangas@google.com>
Date: Tue, 23 Dec 2025 19:34:40 +0000
From: Petteri Kangaslampi <pekangas@...gle.com>
To: kvmarm@...ts.linux.dev
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Vincent Donnefort <vdonnefort@...gle.com>, Joey Gouly <joey.gouly@....com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu <yuzenghui@...wei.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Petteri Kangaslampi <pekangas@...gle.com>
Subject: [PATCH 1/1] KVM: arm64: Fix hyp VA size between layout and MMU

Use a consistent hypervisor VA size between memory layout and MMU
initialization logic when the kernel is configured for less than
IDMAP_VA_BITS of VA space.

Signed-off-by: Petteri Kangaslampi <pekangas@...gle.com>
---
 arch/arm64/kvm/va_layout.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index f6ca0193a96f..76cdd62550e1 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -49,7 +49,7 @@ static void init_hyp_physvirt_offset(void)
 
 /*
  * We want to generate a hyp VA with the following format (with V ==
- * vabits_actual):
+ * hypervisor VA bits):
  *
  *  63 ... V |     V-1    | V-2 .. tag_lsb | tag_lsb - 1 .. 0
  *  ---------------------------------------------------------
@@ -62,10 +62,17 @@ __init void kvm_compute_layout(void)
 {
 	phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
 	u64 hyp_va_msb;
+	u32 hyp_va_bits;
+
+	/*
+	 * We use the bigger of IDMAP_VA_BITS and kernel VA size as the
+	 * hypervisor VA address space size. See mmu.c.
+	 */
+	hyp_va_bits = max(IDMAP_VA_BITS, vabits_actual);
 
 	/* 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(hyp_va_bits - 1);
+	hyp_va_msb ^= BIT(hyp_va_bits - 1);
 
 	tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
 			(u64)(high_memory - 1));
@@ -73,9 +80,9 @@ __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 != (hyp_va_bits - 1)) {
 		/* 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(hyp_va_bits - 2, tag_lsb);
 	}
 	tag_val >>= tag_lsb;
 
-- 
2.52.0.351.gbe84eed79e-goog