From: Chao Gao <chao.gao@intel.com>
To: Qi Ai <aiqi.i7@bytedance.com>
Cc: <seanjc@google.com>, <bp@alien8.de>, <cenjiahui@bytedance.com>,
<dave.hansen@linux.intel.com>, <dengqiao.joey@bytedance.com>,
<fangying.tommy@bytedance.com>, <fengzhimin@bytedance.com>,
<hpa@zytor.com>, <kvm@vger.kernel.org>, <mingo@redhat.com>,
<pbonzini@redhat.com>, <tglx@linutronix.de>
Subject: Re: [PATCH] kvm/x86: clear hlt for intel cpu when resetting vcpu
Date: Wed, 5 Jul 2023 16:40:08 +0800 [thread overview]
Message-ID: <ZKUsaFzoCzjiGNZ1@chao-email> (raw)
In-Reply-To: <20230704113405.3335046-1-aiqi.i7@bytedance.com>
On Tue, Jul 04, 2023 at 07:34:05PM +0800, Qi Ai wrote:
>Reproduce this problem need to use the cpu_pm=on in QEMU, so execute halt in vm doesn't
>cause a vm exit, so mp_state will never be HLT. I am confused why mp_state is considered in this case.
This is just current implementation. It is not necessary to be this way. If
userspace can manipulate vmcs.ACTIVITY_STATE indirectly via mp_state, your
issue will be fixed. But as Sean said, this solution will cause "cascading
effect to a whole pile of things"
>
>And the bsp's vmcs.ACTIVITY_STATE need to reset to ACTIVITY to solve this problem.
>We need a proper set of APIs as you say. In this case, do we only provide a reset ioctl,
>or do we need to report vmcs.ACTIVITY_STATE to the userspace?
The latter I believe. Then userspace can migrate the state. If we go with the
former, the subtle bug pointed out by Sean won't be fixed:
if a vCPU is live migrated, I'm pretty sure vmcs.ACTIVITY_STATE
is lost, which is wrong.
Definitely, we need Sean's confirmation here.
next prev parent reply other threads:[~2023-07-05 8:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-30 7:26 [PATCH] kvm/x86: clear hlt for intel cpu when resetting vcpu Qi Ai
2023-06-30 10:14 ` Chao Gao
2023-06-30 22:23 ` Isaku Yamahata
2023-06-30 22:56 ` Sean Christopherson
2023-07-04 11:34 ` Qi Ai
2023-07-05 8:40 ` Chao Gao [this message]
2023-07-05 9:04 ` Chao Gao
2023-07-31 19:15 ` Sean Christopherson
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