* [Qemu-devel] [PATCH] report revision 3 of the ACPI/SMBus PIIX4 controller
@ 2008-01-11 21:26 Marcelo Tosatti
2008-01-13 10:25 ` [Qemu-devel] Re: [kvm-devel] " Avi Kivity
0 siblings, 1 reply; 2+ messages in thread
From: Marcelo Tosatti @ 2008-01-11 21:26 UTC (permalink / raw)
To: kvm-devel; +Cc: qemu-devel
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.
--- kvm-userspace.orig/qemu/hw/acpi.c
+++ kvm-userspace/qemu/hw/acpi.c
@@ -486,7 +486,7 @@ i2c_bus *piix4_pm_init(PCIBus *bus, int
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
^ permalink raw reply [flat|nested] 2+ messages in thread* [Qemu-devel] Re: [kvm-devel] [PATCH] report revision 3 of the ACPI/SMBus PIIX4 controller
2008-01-11 21:26 [Qemu-devel] [PATCH] report revision 3 of the ACPI/SMBus PIIX4 controller Marcelo Tosatti
@ 2008-01-13 10:25 ` Avi Kivity
0 siblings, 0 replies; 2+ messages in thread
From: Avi Kivity @ 2008-01-13 10:25 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: kvm-devel, qemu-devel
Marcelo Tosatti wrote:
> 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.
>
>
Applied (to kvm's qemu), thanks.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 2+ messages in thread
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2008-01-11 21:26 [Qemu-devel] [PATCH] report revision 3 of the ACPI/SMBus PIIX4 controller Marcelo Tosatti
2008-01-13 10:25 ` [Qemu-devel] Re: [kvm-devel] " Avi Kivity
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