KVM: arm64: Add Fine-Grained UNDEF tracking information

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>
Link: https://lore.kernel.org/r/20240214131827.2856277-18-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 914fd54179bbe9fe7942d61ddfb24aff57ede743..c69b258fc989be8c7647f79353d2bb8c780bf1cc 100644 (file)
--- 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 4f2a32a8f24745b48074ab0dee0dd03dac3cbb9e..b67078b8271bb4fef7ebf19957abc24f723d9da8 100644 (file)
--- 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,