From 486eacda3a8fe32d7359bff36d0caa1b8fffd12b Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Fri, 11 Jan 2008 19:26:55 -0200 Subject: [PATCH] Report revision 3 of the ACPI/SMBus PIIX4 controller The PIIX4 ACPI controller prior to revision 0x3 contains a bug where reading of the timer port is unreliable, so the kernel reads it three times for consistency check. QEMU does not suffer from that problem :) The datasheet for PIIX4, PIIX4E, and PIIX4M is the same. I failed to find any indication that the revision increase could affect anything other than the PMTimer port read. This reduces idle guest CPU consumption from 14% to 8% on 4-way KVM guest. Signed-off-by: Avi Kivity --- hw/acpi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/acpi.c b/hw/acpi.c index b97b37d22a..bfee40b44c 100644 --- a/hw/acpi.c +++ b/hw/acpi.c @@ -486,7 +486,7 @@ i2c_bus *piix4_pm_init(PCIBus *bus, int devfn, uint32_t smb_io_base) pci_conf[0x03] = 0x71; pci_conf[0x06] = 0x80; pci_conf[0x07] = 0x02; - pci_conf[0x08] = 0x00; // revision number + pci_conf[0x08] = 0x03; // revision number pci_conf[0x09] = 0x00; pci_conf[0x0a] = 0x80; // other bridge device pci_conf[0x0b] = 0x06; // bridge device -- 2.11.4.GIT