nexoniarz/SchOS
nexoniarz/SchOS
Watch
1
0
Fork
You've already forked SchOS
 0
Code Issues Pull requests Projects Releases 1 Packages Wiki Activity Actions

irq: MSI first, and poll the INTx lines that never arrive

Browse source 
PCI drivers took their interrupt from INTERRUPT_LINE. On real hardware
that is the 8259's number, not the IOAPIC pin the device is wired to
(that is in ACPI _PRT, which needs AML), so nothing ever arrived. xHCI
is entirely interrupt-driven, so the USB keyboard and a USB root would
have hung even on a clean boot. Under QEMU the two numbers agree,
which is why it never showed.

- pci_irq_attach()/pci_irq_detach(): MSI, then MSI-X if the driver
  allows it, then INTx. The handler is registered before MSI is
  enabled, so no edge is lost. xHCI, e1000, r8169 and rtl8139 use it.
- Lines 24-29 are MSI vectors. The LAPIC error vector moves from 19,
  which is a PCI pin on Intel chipsets, to 30. Nothing is placed at or
  above vector 64 (T_SYSCALL).
- A storming line is masked and its handlers are polled instead of
  being left to eat the CPU. A level line that has had a handler for 2 s
  and never fired is polled every tick by a kernel thread.

Tested in QEMU q35 with the root on a USB stick: xHCI and e1000e on
MSI; then MSI disabled and INTx deliberately misrouted, where xHCI got
zero interrupts and the root still mounted through the poller. i440fx
INTx and the rtl8139 hand-over are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HH7xukt4aaiGj1nQEAoQf1
This commit is contained in:
Nexoniarz 2026-10-22 10:29:24 +02:00
commit 7e8d5e2821
11 changed files with 407 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

20
kernel/drivers/net/e1000/e1000.c
View file

@ -359,19 +359,20 @@ e1000_probe(struct pci_dev *d)
wr(e, E1000_RCTL, E1000_RCTL_EN | E1000_RCTL_BAM | E1000_RCTL_SECRC |
E1000_RCTL_SZ_2048 | E1000_RCTL_LBM_NONE);
if (d->irq != 0xFF)
// level_low = 1: this is a PCI interrupt, which is level-triggered and
// active low. Registering it as edge-triggered makes it fire once and then
// wedge, because the device holds the line asserted and no further edge
// ever arrives. See the comment on irq_register in include/irq.h.
irq_register(d->irq, e1000_intr, e, "e1000", 1);
// MSI where the part has it -- the 82574 and the rest of the PCIe
// generation do -- and INTx otherwise. MSI-X is not offered: the 82574 in
// MSI-X mode routes its causes through IVAR, which this driver does not
// program, and its interrupts would go nowhere. If neither works the
// network thread still collects frames on its tick.
pci_irq_attach(d, e1000_intr, e, "e1000", 0);
wr(e, E1000_IMS, E1000_ICR_RXT0 | E1000_ICR_RXDMT0 | E1000_ICR_LSC);
e->ready = 1;
kinfo("e1000: %x:%x:%x:%x:%x:%x, link %s, irq %d\n",
kinfo("e1000: %x:%x:%x:%x:%x:%x, link %s, irq %d (%s)\n",
e->mac[0], e->mac[1], e->mac[2], e->mac[3], e->mac[4], e->mac[5],
(rd(e, E1000_STATUS) & E1000_STATUS_LU) ? "up" : "down", d->irq);
(rd(e, E1000_STATUS) & E1000_STATUS_LU) ? "up" : "down",
d->irq_line, pci_irq_kind(d));
return 0;
}
@ -458,8 +459,7 @@ e1000_release(struct pci_dev *d)
wr(e, E1000_TCTL, 0); // stop transmitting
rd(e, E1000_STATUS); // post the writes
if (d->irq != 0xFF)
irq_unregister(d->irq, e1000_intr, e);
pci_irq_detach(d, e1000_intr, e);
// And take the interface out of the stack.
//