leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

KVM: x86: acknowledgment mechanism for async pf page ready notifications

Browse Source 
If two page ready notifications happen back to back the second one is not
delivered and the only mechanism we currently have is
kvm_check_async_pf_completion() check in vcpu_run() loop. The check will
only be performed with the next vmexit when it happens and in some cases
it may take a while. With interrupt based page ready notification delivery
the situation is even worse: unlike exceptions, interrupts are not handled
immediately so we must check if the slot is empty. This is slow and
unnecessary. Introduce dedicated MSR_KVM_ASYNC_PF_ACK MSR to communicate
the fact that the slot is free and host should check its notification
queue. Mandate using it for interrupt based 'page ready' APF event
delivery.

As kvm_check_async_pf_completion() is going away from vcpu_run() we need
a way to communicate the fact that vcpu->async_pf.done queue has
transitioned from empty to non-empty state. Introduce
kvm_arch_async_page_present_queued() and KVM_REQ_APF_READY to do the job.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200525144125.143875-7-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov
2020-05-25 16:41:21 +02:00
committed by Paolo Bonzini
parent 2635b5c4a0
commit 557a961abb
6 changed files with 52 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/uapi/asm/kvm_para.h
View File

@@ -51,6 +51,7 @@
#define MSR_KVM_PV_EOI_EN 0x4b564d04
#define MSR_KVM_POLL_CONTROL 0x4b564d05
#define MSR_KVM_ASYNC_PF_INT 0x4b564d06
#define MSR_KVM_ASYNC_PF_ACK 0x4b564d07
struct kvm_steal_time {
__u64 steal;