linux-kernel - Re: [GIT PULL] KVM fixes for 4.10 merge window

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Date:   Sat, 17 Dec 2016 11:09:16 +0800
From:   Pan Xinhui <xinhui@...ux.vnet.ibm.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KVM list <kvm@...r.kernel.org>
Subject: Re: [GIT PULL] KVM fixes for 4.10 merge window



在 2016/12/17 03:42, Linus Torvalds 写道:
> On Fri, Dec 16, 2016 at 8:57 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>>
>>   git://git.kernel.org/pub/scm/virt/kvm/kvm.git tags/for-linus
>
> This piece-of-shit branch has obviously never been even compile-tested:
>
>   arch/x86/kernel/kvm.c: In function ‘__kvm_vcpu_is_preempted’:
>   arch/x86/kernel/kvm.c:596:14: error: ‘struct kvm_steal_time’ has no
> member named ‘preempted’
>
hi, Linus
	oh, my bad also. I introduce this struct member and use it in same patch.
Better to separate tem into two patches. I make one fix patch below. sorry again.

Hi, Paolo
	I have known where is th problem, I think if we can set this ->preempted later after preempted_enable()
or just introduce something like write_guest_nosleep (per cpu memory section in guest, so there is no page_fault or any other cannot sleep problems)?

thanks
xinhui
-----------------
 From d4fa3ea0b8b6f3e5ff511604a4a6665d1cbb74c3 Mon Sep 17 00:00:00 2001
From: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Date: Sat, 17 Dec 2016 02:56:33 -0500
Subject: [PATCH] kvm: fix compile issue

we revert commit 0b9f6c4615c993d2b552e0d2bd1ade49b56e5beb which calls
sleep function while preempt_disable on host part. But we remove struct
kvm_steal_time::preempted too. This casues compile problem as both guest
and host code use it.

Fix it by adding struct kvm_steal_time::preempted back.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
  arch/x86/include/uapi/asm/kvm_para.h | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 94dc8ca..1421a65 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -45,7 +45,9 @@ struct kvm_steal_time {
  	__u64 steal;
  	__u32 version;
  	__u32 flags;
-	__u32 pad[12];
+	__u8  preempted;
+	__u8  u8_pad[3];
+	__u32 pad[11];
  };
  
  #define KVM_STEAL_ALIGNMENT_BITS 5
-- 
2.4.11

> where commit b94c3698b4b0 ("Revert "x86/kvm: Support the vCPU
> preemption check"") removed the "preempted" field from struct
> kvm_steal_time, but you left this in place:
>
>   __visible bool __kvm_vcpu_is_preempted(int cpu)
>   {
>           struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
>
>           return !!src->preempted;
>   }
>
> And no, that is not a merge artifact in my tree (although that
> function did come in from Ingo). That compile failure comes from your
> very own branch.
>
> Am I upset? You bet I am. Get your act together. You can't just
> randomly revert things without checking the end result.
>
>              Linus
>