[PATCH] hw/net: e1000e: Clear ICR on read when using non MSI-X interrupts

[Nick Hudson <skrll@netbsd.org>]

In section 7.4.3 of the 82574 datasheet it states that

    "In systems that do not support MSI-X, reading the ICR
     register clears it's bits..."

Some OSes rely on this.

Signed-off-by: Nick Hudson <skrll@netbsd.org>
---
 hw/net/e1000e_core.c | 5 +++++
 hw/net/trace-events  | 1 +
 2 files changed, 6 insertions(+)

diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
index 8ae6fb7e14..2c51089a82 100644
--- a/hw/net/e1000e_core.c
+++ b/hw/net/e1000e_core.c
@@ -2607,6 +2607,11 @@ e1000e_mac_icr_read(E1000ECore *core, int index)
         core->mac[ICR] = 0;
     }
 
+    if (!msix_enabled(core->owner)) {
+        trace_e1000e_irq_icr_clear_nonmsix_icr_read();
+        core->mac[ICR] = 0;
+    }
+
     if ((core->mac[ICR] & E1000_ICR_ASSERTED) &&
         (core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
         trace_e1000e_irq_icr_clear_iame();
diff --git a/hw/net/trace-events b/hw/net/trace-events
index 643338f610..084086ec44 100644
--- a/hw/net/trace-events
+++ b/hw/net/trace-events
@@ -221,6 +221,7 @@ e1000e_irq_write_ics(uint32_t val) "Adding ICR bits 0x%x"
 e1000e_irq_icr_process_iame(void) "Clearing IMS bits due to IAME"
 e1000e_irq_read_ics(uint32_t ics) "Current ICS: 0x%x"
 e1000e_irq_read_ims(uint32_t ims) "Current IMS: 0x%x"
+e1000e_irq_icr_clear_nonmisx_icr_read(void) "Clearing ICR on read due to non MSI-X int"
 e1000e_irq_icr_read_entry(uint32_t icr) "Starting ICR read. Current ICR: 0x%x"
 e1000e_irq_icr_read_exit(uint32_t icr) "Ending ICR read. Current ICR: 0x%x"
 e1000e_irq_icr_clear_zero_ims(void) "Clearing ICR on read due to zero IMS"
-- 
2.25.1