arch: AArch64: Porting GIC dist_regs implementation

This commit ports the implementation of GIC distributor registers
from Firecracker.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

arch/src/aarch64/gic/dist_regs.rs

@@ -0,0 +1,182 @@
+// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use super::{Error, Result};
+use crate::layout::IRQ_BASE;
+use hypervisor::kvm::kvm_bindings::{
+    kvm_device_attr, KVM_DEV_ARM_VGIC_GRP_DIST_REGS, KVM_DEV_ARM_VGIC_GRP_NR_IRQS,
+};
+use std::sync::Arc;
+
+/*
+ Distributor registers as detailed at page 456 from
+ https://static.docs.arm.com/ihi0069/c/IHI0069C_gic_architecture_specification.pdf.
+ Address offsets are relative to the Distributor base address defined
+by the system memory map. Unless otherwise stated in the register description,
+all GIC registers are 32-bits wide.
+ */
+const GICD_CTLR: u32 = 0x0;
+const GICD_STATUSR: u32 = 0x0010;
+const GICD_IGROUPR: u32 = 0x0080;
+const GICD_ISENABLER: u32 = 0x0100;
+const GICD_ICENABLER: u32 = 0x0180;
+const GICD_ISPENDR: u32 = 0x0200;
+const GICD_ICPENDR: u32 = 0x0280;
+const GICD_ISACTIVER: u32 = 0x0300;
+const GICD_ICACTIVER: u32 = 0x0380;
+const GICD_IPRIORITYR: u32 = 0x0400;
+const GICD_ICFGR: u32 = 0x0C00;
+const GICD_IROUTER: u32 = 0x6000;
+
+/// This is how we represent the registers of the vgic's distributor.
+/// Some of the distributor register )(i.e GICD_STATUSR) are simple
+/// registers (i.e they are associated to a 32 bit value).
+/// However, there are other registers that have variable lengths since
+/// they dedicate some of the 32 bits to some specific interrupt. So, their length
+/// depends on the number of interrupts (i.e the ones that are represented as GICD_REG<n>)
+/// in the documentation mentioned above.
+struct DistReg {
+    /// Offset from distributor address.
+    base: u32,
+    /// Bits per interrupt.
+    /// Relevant for registers that DO share IRQs.
+    bpi: u8,
+    /// Length of the register.
+    /// Relevant for registers that DO NOT share IRQs.
+    length: u16,
+}
+
+// All or at least the registers we are interested in are 32 bit, so
+// we use a constant for size(u32).
+const REG_SIZE: u8 = 4;
+
+// Creates a vgic distributor register.
+macro_rules! VGIC_DIST_REG {
+    ($base:expr, $bpi:expr, $length:expr) => {
+        DistReg {
+            base: $base,
+            bpi: $bpi,
+            length: $length,
+        }
+    };
+}
+
+// List with relevant distributor registers that we will be restoring.
+// Order is taken from qemu.
+static VGIC_DIST_REGS: &'static [DistReg] = &[
+    VGIC_DIST_REG!(GICD_STATUSR, 0, 4),
+    VGIC_DIST_REG!(GICD_ICENABLER, 1, 0),
+    VGIC_DIST_REG!(GICD_ISENABLER, 1, 0),
+    VGIC_DIST_REG!(GICD_IGROUPR, 1, 0),
+    VGIC_DIST_REG!(GICD_IROUTER, 64, 0),
+    VGIC_DIST_REG!(GICD_ICFGR, 2, 0),
+    VGIC_DIST_REG!(GICD_ICPENDR, 1, 0),
+    VGIC_DIST_REG!(GICD_ISPENDR, 1, 0),
+    VGIC_DIST_REG!(GICD_ICACTIVER, 1, 0),
+    VGIC_DIST_REG!(GICD_ISACTIVER, 1, 0),
+    VGIC_DIST_REG!(GICD_IPRIORITYR, 8, 0),
+];
+
+fn dist_attr_access(
+    gic: &Arc<dyn hypervisor::Device>,
+    offset: u32,
+    val: &u32,
+    set: bool,
+) -> Result<()> {
+    let mut gic_dist_attr = kvm_device_attr {
+        group: KVM_DEV_ARM_VGIC_GRP_DIST_REGS,
+        attr: offset as u64,
+        addr: val as *const u32 as u64,
+        flags: 0,
+    };
+    if set {
+        gic.set_device_attr(&gic_dist_attr)
+            .map_err(Error::SetDeviceAttribute)?;
+    } else {
+        gic.get_device_attr(&mut gic_dist_attr)
+            .map_err(Error::GetDeviceAttribute)?;
+    }
+    Ok(())
+}
+
+/// Get the distributor control register.
+pub fn read_ctlr(gic: &Arc<dyn hypervisor::Device>) -> Result<u32> {
+    let val: u32 = 0;
+    dist_attr_access(gic, GICD_CTLR, &val, false)?;
+    Ok(val)
+}
+
+/// Set the distributor control register.
+pub fn write_ctlr(gic: &Arc<dyn hypervisor::Device>, val: u32) -> Result<()> {
+    dist_attr_access(gic, GICD_CTLR, &val, true)
+}
+
+fn get_interrupts_num(gic: &Arc<dyn hypervisor::Device>) -> Result<u32> {
+    let num_irq = 0;
+
+    let mut nr_irqs_attr = kvm_device_attr {
+        group: KVM_DEV_ARM_VGIC_GRP_NR_IRQS,
+        attr: 0,
+        addr: &num_irq as *const u32 as u64,
+        flags: 0,
+    };
+    gic.get_device_attr(&mut nr_irqs_attr)
+        .map_err(Error::GetDeviceAttribute)?;
+    Ok(num_irq)
+}
+
+fn compute_reg_len(gic: &Arc<dyn hypervisor::Device>, reg: &DistReg, base: u32) -> Result<u32> {
+    let mut end = base;
+    let num_irq = get_interrupts_num(gic)?;
+    if reg.length > 0 {
+        // This is the single type register (i.e one that is not DIST_X<n>) and for which
+        // the bpi is 0.
+        // Look in the kernel for REGISTER_DESC_WITH_LENGTH.
+        end = base + reg.length as u32;
+    }
+    if reg.bpi > 0 {
+        // This is the type of register that takes into account the number of interrupts
+        // that the model has. It is also the type of register where
+        // a register relates to multiple interrupts.
+        end = base + (reg.bpi as u32 * (num_irq - IRQ_BASE) / 8);
+        if reg.bpi as u32 * (num_irq - IRQ_BASE) % 8 > 0 {
+            end += REG_SIZE as u32;
+        }
+    }
+    Ok(end)
+}
+
+/// Set distributor registers of the GIC.
+pub fn set_dist_regs(gic: &Arc<dyn hypervisor::Device>, state: &[u32]) -> Result<()> {
+    let mut idx = 0;
+
+    for dreg in VGIC_DIST_REGS {
+        let mut base = dreg.base + REG_SIZE as u32 * dreg.bpi as u32;
+        let end = compute_reg_len(gic, &dreg, base)?;
+
+        while base < end {
+            let val = state[idx];
+            dist_attr_access(gic, base, &val, true)?;
+            idx += 1;
+            base += REG_SIZE as u32;
+        }
+    }
+    Ok(())
+}
+/// Get distributor registers of the GIC.
+pub fn get_dist_regs(gic: &Arc<dyn hypervisor::Device>) -> Result<Vec<u32>> {
+    let mut state = Vec::new();
+
+    for dreg in VGIC_DIST_REGS {
+        let mut base = dreg.base + REG_SIZE as u32 * dreg.bpi as u32;
+        let end = compute_reg_len(gic, &dreg, base)?;
+
+        while base < end {
+            let val: u32 = 0;
+            dist_attr_access(gic, base, &val, false)?;
+            state.push(val);
+            base += REG_SIZE as u32;
+        }
+    }
+    Ok(state)
+}

arch/src/aarch64/gic/mod.rs

@@ -1,10 +1,12 @@
 // Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+pub mod dist_regs;
 mod gicv2;
 mod gicv3;
 mod gicv3_its;
 
+pub use self::dist_regs::{get_dist_regs, read_ctlr, set_dist_regs, write_ctlr};
 use std::result;
 use std::sync::Arc;