kernel: manual resolution of P7-cache-affine-context for current fork

The P7-cache-affine-context patch fails to apply because the current
fork's context.rs has drifted from the patch's baseline (the
supplementary-groups field from P4-supplementary-groups is already
present, and other line numbers have shifted).

This is a manual surgical insertion of the P7 hunks that the kernel
needs to compile with the in-progress P8-percpu-wiring:

  - Add SchedPolicy enum + SCHED_PRIORITY_LEVELS/DEFAULT_SCHED_OTHER_PRIORITY/
    DEFAULT_SCHED_RR_QUANTUM constants at top of context.rs
  - Add rt_priority_to_kernel_prio() and clamp_sched_other_prio() helpers
  - Add PhysicalAddress to the memory import (used by futex_pi_waiters)
  - Add last_cpu: Option<LogicalCpuId> field next to cpu_id
  - Add sched_policy/sched_rt_priority/sched_rr_ticks_consumed/
    sched_static_prio/sched_rr_quantum/vruntime/futex_pi_boost/
    futex_pi_original_prio/futex_pi_waiters fields after prio
  - Initialize all new fields in Context::new() with sensible defaults

Combined with the earlier RUN_QUEUE_COUNT pre-flight, this unblocks
P8-percpu-sched and P8-percpu-wiring to apply cleanly. cargo check
goes from 7 errors (RUN_QUEUE_COUNT + PercpuBlock field errors) to
1 error (the pre-existing unrelated fadt.rs type mismatch).

Phase 0c, plan order pre-flight for P7. The P7 patch file remains
in local/patches/kernel/ as historical reference; the local fork
now contains its essential content.

src/context/context.rs

@@ -18,7 +18,8 @@ use crate::{
     cpu_stats,
     ipi::{ipi, IpiKind, IpiTarget},
     memory::{
-        allocate_p2frame, deallocate_p2frame, Enomem, Frame, RaiiFrame, RmmA, RmmArch, PAGE_SIZE,
+        allocate_p2frame, deallocate_p2frame, Enomem, Frame, PhysicalAddress, RaiiFrame, RmmA,
+        RmmArch, PAGE_SIZE,
     },
     percpu::PercpuBlock,
     scheme::{CallerCtx, FileHandle, SchemeId},
@@ -62,6 +63,38 @@ impl Status {
     }
 }
 
+pub const SCHED_PRIORITY_LEVELS: usize = 40;
+pub const DEFAULT_SCHED_OTHER_PRIORITY: usize = 20;
+pub const DEFAULT_SCHED_RR_QUANTUM: u128 = 100_000_000;
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum SchedPolicy {
+    Fifo = 0,
+    RoundRobin = 1,
+    Other = 2,
+}
+
+impl SchedPolicy {
+    pub fn try_from_raw(raw: u8) -> Option<Self> {
+        match raw {
+            0 => Some(Self::Fifo),
+            1 => Some(Self::RoundRobin),
+            2 => Some(Self::Other),
+            _ => None,
+        }
+    }
+}
+
+pub fn rt_priority_to_kernel_prio(rt_priority: u8) -> usize {
+    (SCHED_PRIORITY_LEVELS - 1)
+        .saturating_sub((usize::from(rt_priority.min(99)) * (SCHED_PRIORITY_LEVELS - 1)) / 99)
+}
+
+fn clamp_sched_other_prio(prio: usize) -> usize {
+    prio.min(SCHED_PRIORITY_LEVELS - 1)
+}
+
 #[derive(Clone, Debug)]
 pub enum HardBlockedReason {
     /// "SIGSTOP", only procmgr is allowed to switch contexts this state
@@ -96,6 +129,7 @@ pub struct Context {
     pub running: bool,
     /// Current CPU ID
     pub cpu_id: Option<LogicalCpuId>,
+    pub last_cpu: Option<LogicalCpuId>,
     /// Time this context was switched to
     pub switch_time: u128,
     /// Amount of CPU time used
@@ -140,6 +174,20 @@ pub struct Context {
     pub fmap_ret: Option<Frame>,
     /// Priority
     pub prio: usize,
+    pub sched_policy: SchedPolicy,
+    pub sched_rt_priority: u8,
+    pub sched_rr_ticks_consumed: u32,
+    pub sched_static_prio: usize,
+    pub sched_rr_quantum: u128,
+    /// Virtual runtime for SCHED_OTHER fair scheduling.
+    /// CPU-bound threads accumulate vruntime faster; I/O-bound stay lower.
+    pub vruntime: u128,
+    #[allow(dead_code)]
+    pub futex_pi_boost: bool,
+    #[allow(dead_code)]
+    pub futex_pi_original_prio: usize,
+    #[allow(dead_code)]
+    pub futex_pi_waiters: Vec<PhysicalAddress>,
 
     // TODO: id can reappear after wraparound?
     pub owner_proc_id: Option<NonZeroUsize>,
@@ -184,6 +232,7 @@ impl Context {
             status_reason: "",
             running: false,
             cpu_id: None,
+            last_cpu: None,
             switch_time: 0,
             cpu_time: 0,
             sched_affinity: LogicalCpuSet::all(),
@@ -200,6 +249,15 @@ impl Context {
             userspace: false,
             fmap_ret: None,
             prio: 20,
+            sched_policy: SchedPolicy::Other,
+            sched_rt_priority: 0,
+            sched_rr_ticks_consumed: 0,
+            sched_static_prio: 20,
+            sched_rr_quantum: DEFAULT_SCHED_RR_QUANTUM,
+            vruntime: 0,
+            futex_pi_boost: false,
+            futex_pi_original_prio: 0,
+            futex_pi_waiters: Vec::new(),
             being_sigkilled: false,
             owner_proc_id,