add QEMU pvpanic ISA device

[hawkw]

This branch adds support for the pvpanic virtual device implemented by
QEMU. This device allows guests to report kernel panics to the
hypervisor. In propolis-server, guest-reported kernel panics are
handled by incrementing an Oximeter metric.

The pvpanic device can be exposed to the guest either as an ISA bus I/O
port device or as a PCI bus device. This branch implements the ISA bus
device. I'd like to also add a PCI pvpanic device, but will implement
that in a subsequent pull request.

In order for the guest to detect the ISA bus pvpanic device, it's
necessary to add an entry for the panic device to the ACPI DSDT table.
This is the AML that QEMU adds to its DSDT when the ISA bus pvpanic
device is enabled:

//
// QEMU panic device
//
Device (PEVT)
{
    Name (_HID, "QEMU0001")  // _HID: Hardware ID
    Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
    {
        IO (Decode16,
            0x0505,             // Range Minimum
            0x0505,             // Range Maximum
            0x01,               // Alignment
            0x01,               // Length
            )
    })
    OperationRegion (PEOR, SystemIO, 0x0505, One)
    Field (PEOR, ByteAcc, NoLock, Preserve)
    {
        PEPT,   8
    }

    Name (_STA, 0x0F)  // _STA: Status
    Method (RDPT, 0, NotSerialized)
    {
        Local0 = PEPT /* \_SB_.PCI0.S08_.PEVT.PEPT */
        Return (Local0)
    }

    Method (WRPT, 1, NotSerialized)
    {
        PEPT = Arg0
    }
}

This means that in order for guests to use this device, we need to boot
with an ACPI table that contains this entry. For testing purposes, I
modified EDK2 OVMF to add this entry to the DSDT. In the future, though,
we'll likely want Propolis to generate ACPI tables dynamically on boot
based on the instance spec.

The EDK2 changes I used for testing this are available here.

To test this change, I ran propolis-standalone with an Alpine Linux
3.19 guest,, and the following device added to the VM config file:

[dev.pvpanic]
driver = "qemu-pvpanic"
enable_mmio = true

The guest correctly detects the panic device and loads the appropriate
kernel module. If I then trigger a panic in the guest using SysRq, like
this:

$ echo 1 > /proc/sys/kernel/sysrq
$ echo c > /proc/sysrq-trigger

The guest crashes, and propolis-standalone logs:

dev: pvpanic
 Jan 11 18:14:13.494 DEBG guest kernel panic, guest_handled: false, host_handled: true

Closes #592

[pfmooney]

Thanks for drawing this up.

[github-actions]

license-eye has totally checked 254 files.

Valid	Invalid	Ignored	Fixed
189	1	64	0

Click to see the invalid file list

• bin/propolis-server/src/lib/stats/pvpanic.rs

[gjcolombo]

This is looking good! A few comments on how we want the instance spec side of this to look:

[gjcolombo]

LGTM with one small tweak. (I didn't leave any additional comments on it, but the device emulation also seems fine to me, modulo any other feedback @pfmooney might have.)

Thanks for putting this together!