Marcelo Tosatti wrote:
QEMU support for direct pmtimer reads. Hopefully its safe, since its a
read-only register ?
With self-disable C2 + this I'm seeing less CPU usage when idle with
CONFIG_CPU_IDLE enabled. Quite noticeable on SMP guests. Windows XP is
comparable to standard (never seen it consume less than 10% either way,
usually 20-30%).
This is because the TPR optimization hack is disabled on smp. You need
a machine with FlexPriority to get usable smp Windows.
On migration the destination host can either lack ACPI or have the timer
in a different IO port, so emulation is necessary.
Or luckily the pmtimer is in the same address. Since the 24-bit counter
overflow period is only ~= 4.6 seconds, its probably worthwhile to wait
for synchronization before restarting the guest. Not implemented though.
Also simplify and fix the overflow emulation, which was happening every
2.3 seconds instead of the expected 4.6s.
Index: kvm-userspace.tip/bios/rombios32.c
===================================================================
--- kvm-userspace.tip.orig/bios/rombios32.c
+++ kvm-userspace.tip/bios/rombios32.c
@@ -391,7 +391,7 @@ uint8_t bios_uuid[16];
unsigned long ebda_cur_addr;
#endif
int acpi_enabled;
-uint32_t pm_io_base, smb_io_base;
+uint32_t pm_io_base, pmtmr_base, smb_io_base;
int pm_sci_int;
unsigned long bios_table_cur_addr;
unsigned long bios_table_end_addr;
@@ -819,6 +819,12 @@ static void pci_bios_init_device(PCIDevi
pci_config_writeb(d, PCI_INTERRUPT_LINE, 9);
pm_io_base = PM_IO_BASE;
+ pmtmr_base = cmos_readb(0x60);
+ pmtmr_base |= cmos_readb(0x61) << 8;
+ pmtmr_base |= cmos_readb(0x62) << 16;
+ pmtmr_base |= cmos_readb(0x63) << 24;
+ if (!pmtmr_base)
+ pmtmr_base = pm_io_base + 0x08;
You're splitting the ACPI ioport range into two. I think the correct
fix here is to have qemu supply a PMBA hint to the BIOS. If the hint is
present, the bios should locate pm_io_base there, and should also avoid
placing other pio resources there.
+static void schedule_pmtmr_sci(PIIX4PMState *s)
+{
+ int64_t expire_time;
+ uint32_t pmtmr, left;
+
+ if (s->direct_access)
+ qemu_kvm_get_pmtimer(&pmtmr);
+ else
+ pmtmr = get_pmtmr(s);
get_pmtmr() should have this logic.
+
+ left = (1 << 24) - pmtmr;
The docs say that SCI is generated when bit 23 toggles, not on
overflow. See TMROF_STS PIIX4 documentation.
In any case, this should be in a separate patch.
--
error compiling committee.c: too many arguments to function
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