Re: [PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-22 Thread Yin Fengwei
On 2019/10/18 下午6:12, Rafael J. Wysocki wrote: On Wednesday, October 16, 2019 7:56:17 AM CEST Yin, Fengwei wrote: Hi David, On 10/15/2019 7:48 PM, David Laight wrote: From: Yin Fengwei Sent: 15 October 2019 09:04 In function acpi_idle_do_entry(), an ioport access is used for dummy wait to

Re: [PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-18 Thread Yin, Fengwei
On 10/18/2019 6:12 PM, Rafael J. Wysocki wrote: On Wednesday, October 16, 2019 7:56:17 AM CEST Yin, Fengwei wrote: Hi David, On 10/15/2019 7:48 PM, David Laight wrote: From: Yin Fengwei Sent: 15 October 2019 09:04 In function acpi_idle_do_entry(), an ioport access is used for dummy wait to

Re: [PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-18 Thread Rafael J. Wysocki
On Wednesday, October 16, 2019 7:56:17 AM CEST Yin, Fengwei wrote: > Hi David, > > On 10/15/2019 7:48 PM, David Laight wrote: > > From: Yin Fengwei > >> Sent: 15 October 2019 09:04 > >> In function acpi_idle_do_entry(), an ioport access is used for dummy > >> wait to guarantee hardware behavior.

Re: [PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-15 Thread Yin, Fengwei
Hi David, On 10/15/2019 7:48 PM, David Laight wrote: From: Yin Fengwei Sent: 15 October 2019 09:04 In function acpi_idle_do_entry(), an ioport access is used for dummy wait to guarantee hardware behavior. But it could trigger unnecessary vmexit in virtualization environment. If we run linux

RE: [PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-15 Thread David Laight
From: Yin Fengwei > Sent: 15 October 2019 09:04 > In function acpi_idle_do_entry(), an ioport access is used for dummy > wait to guarantee hardware behavior. But it could trigger unnecessary > vmexit in virtualization environment. > > If we run linux as guest and export all available native C

[PATCH v2] ACPI / processor_idle: use ndelay instead of io port access for wait

2019-10-15 Thread Yin Fengwei
In function acpi_idle_do_entry(), an ioport access is used for dummy wait to guarantee hardware behavior. But it could trigger unnecessary vmexit in virtualization environment. If we run linux as guest and export all available native C state to guest, we did see many PM timer access triggered