rename hv -> paravirt

src/arch/amd64/paravirt/kvm.zig

@@ -0,0 +1,102 @@
+//! KVM paravirtualization support.
+const std = @import("std");
+const amd64 = @import("../root.zig");
+
+pub const Features = packed struct(u32) {
+    clocksource: bool,
+    nop_io_delay: bool,
+    mmu_op: bool,
+    clocksource2: bool,
+    async_pf: bool,
+    steal_time: bool,
+    pv_eoi: bool,
+    pv_unhalt: bool,
+    _reserved0: u1,
+    pv_tlb_flush: bool,
+    async_pf_vmexit: bool,
+    pv_send_ipi: bool,
+    pv_poll_control: bool,
+    pv_sched_yield: bool,
+    async_pf_int: bool,
+    msi_ext_dest_id: bool,
+    hc_map_gpa_range: bool,
+    migration_control: bool,
+    _reserved1: u14,
+};
+
+pub const Info = struct {
+    features: Features,
+};
+
+const Msr = enum(u32) {
+    SystemTime = 0x4B564D01,
+    WallClock = 0x4B564D00,
+    AsyncPf = 0x4B564D02,
+    AsyncPfEn = 0x4B564D03,
+    StealTime = 0x4B564D04,
+    PvEoi = 0x4B564D05,
+    AsyncPfInt = 0x4B564D06,
+    _,
+};
+
+fn read_msr(msr: Msr) u64 {
+    return amd64.rdmsr(@intFromEnum(msr));
+}
+
+fn write_msr(msr: Msr, value: u64) void {
+    amd64.wrmsr(@intFromEnum(msr), value);
+}
+
+const PVClock = extern struct {
+    version: u32,
+    pad0: u32,
+    tsc_timestamp: u64,
+    system_time: u64,
+    tsc_to_system_mul: u32,
+    tsc_shift: i8,
+    flags: u8,
+    pad1: [2]u8,
+};
+
+pub const PVClockSource = struct {
+    page: *volatile PVClock,
+    time_at_boot: u64,
+
+    pub fn read(self: *PVClockSource) u64 {
+        while (true) {
+            const ver = @atomicLoad(u32, &self.page.version, .acquire);
+            if (ver & 1 != 0) continue;
+
+            const tsc_shift = self.page.tsc_shift;
+            const tsc_delta = amd64.rdtsc() - self.page.tsc_timestamp;
+            const shifted = if (tsc_shift >= 0)
+                tsc_delta << @intCast(tsc_shift)
+            else
+                tsc_delta >> @intCast(-tsc_shift);
+            const ns = self.page.system_time +
+                (shifted * @as(u128, self.page.tsc_to_system_mul) >> 32);
+
+            if (@atomicLoad(u32, &self.page.version, .acquire) == ver)
+                return @as(u64, @truncate(ns)) - self.time_at_boot;
+        }
+    }
+
+    pub fn init(phys_page: usize, virt_page: usize) PVClockSource {
+        const page: *volatile PVClock = @ptrFromInt(virt_page);
+        write_msr(.SystemTime, phys_page | 1);
+        var src = PVClockSource{ .page = page, .time_at_boot = 0 };
+        src.time_at_boot = src.read();
+        return src;
+    }
+};
+
+pub fn detect(highest_function: u32) Info {
+    if (highest_function < 0x40000001) {
+        return .{ .features = @bitCast(@as(u32, 0)) };
+    }
+
+    const r = amd64.cpuid(0x40000001, 0);
+    return Info{
+        .features = @bitCast(r.eax),
+    };
+}