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hv: Add IO request completion polling feature

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This patch introduce a new mode of IO request completion, polling mode.

Now, the sketch of ioreq process can be,
  A. UOS vcpu0 generate PIO/MMIO ->
   B. pcpu1(vcpu0 of UOS) trap into HV ->
    C. pcpu1 build ioreq, send IPI and enter idle ->
     D.1 pcpu0(vcpu0 of SOS) response IPI,
     D.2 pcpu0 handle the ioreq in HV, kernel, DM,
     D.3 pcpu0 mark ioreq as complete,
     D.4 pcpu0 hypercall to enter HV ->
       E.1 pcpu0 send IPI to wake pcpu1 up
       E.2 UOS vcpu0 continue running

With this change, it skips D.4, E.1 steps. In step C, pcpu1 will enter a
polling ioreq state idle after send out the IPI.
It can save about ~5000 cpu cycles.

In polling mode, we do the polling in idle instead of pause cpu all the
time. It will consume more power. A better way is to use monitor/mwait
instructions which can put cpu into a sleep state with monitoring a
memory address. Unfortunately, APL has bug with monitor. We can gather
all ioreqs state into one monitorable memory and take advantage of
monitor/mwait for future platform.

The way polling or notification is per VM. We can config VMs in
different mode. By default, IO request completion will use notification
mode for all VMs. We can switch it by Kconfig.

Tracked-On: #1821
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Reviewed-by: Eddie Dong <eddie.dong@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>
This commit is contained in:
Shuo Liu
2018-10-11 14:10:30 +08:00
committed by lijinxia
parent e350abe40d
commit e8296dce05
8 changed files with 103 additions and 4 deletions
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22
hypervisor/arch/x86/Kconfig
View File

@@ -40,6 +40,28 @@ config PARTITION_MODE
endchoice
choice
prompt "I/O emulation completion mode"
default IOREQ_NOTIFICATION
help
Select the mode of I/O emulation completion
config IOREQ_NOTIFICATION
bool "Notification mode"
help
When I/O request is completed, SOS will mark the completion status and
notify hypervisor via hypercall. Hypervisor will finish the post work
when notification is received.
config IOREQ_POLLING
bool "Polling mode"
help
When I/O request is completed, SOS will only mark completion status
without notifying hypervisor. Hypervisor will poll the completion
status and finish the post work.
endchoice
config PLATFORM
string
default "uefi" if PLATFORM_UEFI

4
hypervisor/arch/x86/guest/vm.c
View File

@@ -162,6 +162,10 @@ int create_vm(struct vm_description *vm_desc, struct acrn_vm **rtn_vm)
/* Populate return VM handle */
*rtn_vm = vm;
vm->sw.io_shared_page = NULL;
#ifdef CONFIG_IOREQ_POLLING
/* Now, enable IO completion polling mode for all VMs with CONFIG_IOREQ_POLLING. */
vm->sw.is_completion_polling = true;
#endif
status = set_vcpuid_entries(vm);
if (status != 0) {