[PATCH v2 2/6] arm64/mm: Override PARange for !LPA2 and use it consistently

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

When FEAT_LPA{,2} are not implemented, the ID_AA64MMFR0_EL1.PARange and
TCR.IPS values corresponding with 52-bit physical addressing are
reserved.

Setting the TCR.IPS field to 0b110 (52-bit physical addressing) has side
effects, such as how the TTBRn_ELx.BADDR fields are interpreted, and so
it is important that disabling FEAT_LPA2 (by overriding the
ID_AA64MMFR0.TGran fields) also presents a PARange field consistent with
that.

So limit the field to 48 bits unless LPA2 is enabled, and update
existing references to use the override consistently.

Fixes: 352b0395b505 ("arm64: Enable 52-bit virtual addressing for 4k and 16k granule configs")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 arch/arm64/include/asm/assembler.h    | 5 +++++
 arch/arm64/kernel/cpufeature.c        | 2 +-
 arch/arm64/kernel/pi/idreg-override.c | 9 +++++++++
 arch/arm64/kernel/pi/map_kernel.c     | 6 ++++++
 arch/arm64/mm/init.c                  | 7 ++++++-
 5 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 3d8d534a7a77..ad63457a05c5 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -343,6 +343,11 @@ alternative_cb_end
 	// Narrow PARange to fit the PS field in TCR_ELx
 	ubfx	\tmp0, \tmp0, #ID_AA64MMFR0_EL1_PARANGE_SHIFT, #3
 	mov	\tmp1, #ID_AA64MMFR0_EL1_PARANGE_MAX
+#ifdef CONFIG_ARM64_LPA2
+alternative_if_not ARM64_HAS_VA52
+	mov	\tmp1, #ID_AA64MMFR0_EL1_PARANGE_48
+alternative_else_nop_endif
+#endif
 	cmp	\tmp0, \tmp1
 	csel	\tmp0, \tmp1, \tmp0, hi
 	bfi	\tcr, \tmp0, \pos, #3
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6ce71f444ed8..f8cb8a6ab98a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -3478,7 +3478,7 @@ static void verify_hyp_capabilities(void)
 		return;
 
 	safe_mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
-	mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);
+	mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
 	mmfr1 = read_cpuid(ID_AA64MMFR1_EL1);
 
 	/* Verify VMID bits */
diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
index 22159251eb3a..c6b185b885f7 100644
--- a/arch/arm64/kernel/pi/idreg-override.c
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -83,6 +83,15 @@ static bool __init mmfr2_varange_filter(u64 val)
 		id_aa64mmfr0_override.val |=
 			(ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
 		id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
+
+		/*
+		 * Override PARange to 48 bits - the override will just be
+		 * ignored if the actual PARange is smaller, but this is
+		 * unlikely to be the case for LPA2 capable silicon.
+		 */
+		id_aa64mmfr0_override.val |=
+			ID_AA64MMFR0_EL1_PARANGE_48 << ID_AA64MMFR0_EL1_PARANGE_SHIFT;
+		id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_PARANGE_SHIFT;
 	}
 #endif
 	return true;
diff --git a/arch/arm64/kernel/pi/map_kernel.c b/arch/arm64/kernel/pi/map_kernel.c
index f374a3e5a5fe..e57b043f324b 100644
--- a/arch/arm64/kernel/pi/map_kernel.c
+++ b/arch/arm64/kernel/pi/map_kernel.c
@@ -136,6 +136,12 @@ static void noinline __section(".idmap.text") set_ttbr0_for_lpa2(u64 ttbr)
 {
 	u64 sctlr = read_sysreg(sctlr_el1);
 	u64 tcr = read_sysreg(tcr_el1) | TCR_DS;
+	u64 mmfr0 = read_sysreg(id_aa64mmfr0_el1);
+	u64 parange = cpuid_feature_extract_unsigned_field(mmfr0,
+							   ID_AA64MMFR0_EL1_PARANGE_SHIFT);
+
+	tcr &= ~TCR_IPS_MASK;
+	tcr |= parange << TCR_IPS_SHIFT;
 
 	asm("	msr	sctlr_el1, %0		;"
 	    "	isb				;"
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index d21f67d67cf5..2b2289d55eaa 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -280,7 +280,12 @@ void __init arm64_memblock_init(void)
 
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 		extern u16 memstart_offset_seed;
-		u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);
+
+		/*
+		 * Use the sanitised version of id_aa64mmfr0_el1 so that linear
+		 * map randomization can be enabled by shrinking the IPA space.
+		 */
+		u64 mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
 		int parange = cpuid_feature_extract_unsigned_field(
 					mmfr0, ID_AA64MMFR0_EL1_PARANGE_SHIFT);
 		s64 range = linear_region_size -
-- 
2.47.0.338.g60cca15819-goog