linux-kernel - [PATCH] arm64/cpufeatures/kvm: Add ARMv8.9 FEAT_ECBHB bits in ID

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Date: Tue, 11 Jun 2024 12:20:49 +0000
From: Nianyao Tang <tangnianyao@...wei.com>
To: <maz@...nel.org>, <catalin.marinas@....com>, <will@...nel.org>,
	<mark.rutland@....com>, <oliver.upton@...ux.dev>, <broonie@...nel.org>,
	<ardb@...nel.org>, <joey.gouly@....com>, <ryan.roberts@....com>,
	<jeremy.linton@....com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
CC: <tangnianyao@...wei.com>, <guoyang2@...wei.com>
Subject: [PATCH] arm64/cpufeatures/kvm: Add ARMv8.9 FEAT_ECBHB bits in ID_AA64MMFR1 register

Enable ECBHB bits in ID_AA64MMFR1 register as per ARM DDI 0487K.a
specification.

When guest OS read ID_AA64MMFR1_EL1, kvm emulate this reg using
ftr_id_aa64mmfr1 and always return ID_AA64MMFR1_EL1.ECBHB=0 to guest.
It results in guest syscall jump to tramp ventry, which is not needed
in implementation with ID_AA64MMFR1_EL1.ECBHB=1.
Let's make the guest syscall process the same as the host.

Signed-off-by: Nianyao Tang <tangnianyao@...wei.com>
---
 arch/arm64/kernel/cpufeature.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 48e7029f1054..c3913c90797e 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -429,6 +429,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = {
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_ECBHB_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_TIDCP1_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_AFP_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_HCX_SHIFT, 4, 0),
-- 
2.30.0