[PATCH v4 17/26] KVM: arm64: Add Fine-Grained UNDEF tracking information

From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org
Cc: James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
	Mark Brown <broonie@kernel.org>
Subject: [PATCH v4 17/26] KVM: arm64: Add Fine-Grained UNDEF tracking information
Date: Wed, 14 Feb 2024 13:18:18 +0000	[thread overview]
Message-ID: <20240214131827.2856277-18-maz@kernel.org> (raw)
In-Reply-To: <20240214131827.2856277-1-maz@kernel.org>

In order to efficiently handle system register access being disabled,
and this resulting in an UNDEF exception being injected, we introduce
the (slightly dubious) concept of Fine-Grained UNDEF, modeled after
the architectural Fine-Grained Traps.

For each FGT group, we keep a 64 bit word that has the exact same
bit assignment as the corresponding FGT register, where a 1 indicates
that trapping this register should result in an UNDEF exception being
reinjected.

So far, nothing populates this information, nor sets the corresponding
trap bits.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h | 21 +++++++++++++++++++++
 arch/arm64/kvm/emulate-nested.c   | 12 ------------
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 914fd54179bb..c69b258fc989 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -240,9 +240,30 @@ static inline u16 kvm_mpidr_index(struct kvm_mpidr_data *data, u64 mpidr)
 
 struct kvm_sysreg_masks;
 
+enum fgt_group_id {
+	__NO_FGT_GROUP__,
+	HFGxTR_GROUP,
+	HDFGRTR_GROUP,
+	HDFGWTR_GROUP = HDFGRTR_GROUP,
+	HFGITR_GROUP,
+	HAFGRTR_GROUP,
+
+	/* Must be last */
+	__NR_FGT_GROUP_IDS__
+};
+
 struct kvm_arch {
 	struct kvm_s2_mmu mmu;
 
+	/*
+	 * Fine-Grained UNDEF, mimicking the FGT layout defined by the
+	 * architecture. We track them globally, as we present the
+	 * same feature-set to all vcpus.
+	 *
+	 * Index 0 is currently spare.
+	 */
+	u64 fgu[__NR_FGT_GROUP_IDS__];
+
 	/* Interrupt controller */
 	struct vgic_dist	vgic;
 
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 4f2a32a8f247..b67078b8271b 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -1009,18 +1009,6 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
 
 static DEFINE_XARRAY(sr_forward_xa);
 
-enum fgt_group_id {
-	__NO_FGT_GROUP__,
-	HFGxTR_GROUP,
-	HDFGRTR_GROUP,
-	HDFGWTR_GROUP = HDFGRTR_GROUP,
-	HFGITR_GROUP,
-	HAFGRTR_GROUP,
-
-	/* Must be last */
-	__NR_FGT_GROUP_IDS__
-};
-
 enum fg_filter_id {
 	__NO_FGF__,
 	HCRX_FGTnXS,
-- 
2.39.2


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