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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Peter Xu <peterx@redhat.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	kvm@vger.kernel.org, Nadav Amit <namit@cs.technion.ac.il>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/3] kvm: x86: Rename KVM_DEBUGREG_RELOAD to KVM_DEBUGREG_NEED_RELOAD
Date: Fri, 24 Apr 2020 13:29:22 -0700	[thread overview]
Message-ID: <20200424202921.GG30013@linux.intel.com> (raw)
In-Reply-To: <20200424202103.GA48376@xz-x1>

On Fri, Apr 24, 2020 at 04:21:03PM -0400, Peter Xu wrote:
> On Thu, Apr 23, 2020 at 12:09:42PM -0700, Sean Christopherson wrote:
> > On Thu, Apr 16, 2020 at 06:15:07PM +0800, Xiaoyao Li wrote:
> > > To make it more clear that the flag means DRn (except DR7) need to be
> > > reloaded before vm entry.
> > > 
> > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > > ---
> > >  arch/x86/include/asm/kvm_host.h | 2 +-
> > >  arch/x86/kvm/x86.c              | 6 +++---
> > >  2 files changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index c7da23aed79a..f465c76e6e5a 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -511,7 +511,7 @@ struct kvm_pmu_ops;
> > >  enum {
> > >  	KVM_DEBUGREG_BP_ENABLED = 1,
> > >  	KVM_DEBUGREG_WONT_EXIT = 2,
> > > -	KVM_DEBUGREG_RELOAD = 4,
> > > +	KVM_DEBUGREG_NEED_RELOAD = 4,
> > 
> > My vote would be for KVM_DEBUGREG_DIRTY  Any bit that is set switch_db_regs
> > triggers a reload, whereas I would expect a RELOAD flag to be set _every_
> > time a load is needed and thus be the only bit that's checked
> 
> But then shouldn't DIRTY be set as long as KVM_DEBUGREG_BP_ENABLED is set every
> time before vmenter?  Then it'll somehow go back to switch_db_regs, iiuc...
> 
> IIUC RELOAD actually wants to say "reload only for this iteration", that's why
> it's cleared after each reload.  So maybe...  RELOAD_ONCE?

Or FORCE_LOAD, or FORCE_RELOAD?  Those crossed my mind as well.

> (Btw, do we have debug regs tests somewhere no matter inside guest or with
>  KVM_SET_GUEST_DEBUG?)

I don't think so?

  reply	other threads:[~2020-04-24 20:30 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-16 10:15 [RFC PATCH 0/3] kvm: x86: Cleanup and optimazation of switch_db_regs Xiaoyao Li
2020-04-16 10:15 ` [RFC PATCH 1/3] kvm: x86: Rename KVM_DEBUGREG_RELOAD to KVM_DEBUGREG_NEED_RELOAD Xiaoyao Li
2020-04-23 19:09   ` Sean Christopherson
2020-04-24 13:28     ` Xiaoyao Li
2020-04-24 20:21     ` Peter Xu
2020-04-24 20:29       ` Sean Christopherson [this message]
2020-04-24 20:59         ` Peter Xu
2020-04-25  7:48       ` Paolo Bonzini
2020-04-27 14:37         ` Peter Xu
2020-04-27 16:06           ` Xiaoyao Li
2020-04-25  8:07   ` Paolo Bonzini
2020-04-25 16:54     ` Nadav Amit
2020-04-25 19:16       ` Paolo Bonzini
2020-04-16 10:15 ` [RFC PATCH 2/3] kvm: x86: Use KVM_DEBUGREG_NEED_RELOAD instead of KVM_DEBUGREG_BP_ENABLED Xiaoyao Li
2020-04-23 19:29   ` Sean Christopherson
2020-04-24 13:21     ` Xiaoyao Li
2020-04-16 10:15 ` [RFC PATCH 3/3] kvm: x86: skip DRn reload if previous VM exit is DR access VM exit Xiaoyao Li
2020-04-23 19:31   ` Sean Christopherson

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