From: Peter Xu <peterx@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Xiaoyao Li <xiaoyao.li@intel.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: Mon, 27 Apr 2020 10:37:32 -0400 [thread overview]
Message-ID: <20200427143732.GD48376@xz-x1> (raw)
In-Reply-To: <f1c0ba71-1c5b-a5b7-3123-7ab36a5c5c74@redhat.com>
On Sat, Apr 25, 2020 at 09:48:17AM +0200, Paolo Bonzini wrote:
> On 24/04/20 22:21, Peter Xu wrote:
> > 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?
> >
> > (Btw, do we have debug regs tests somewhere no matter inside guest or with
> > KVM_SET_GUEST_DEBUG?)
>
> What about KVM_DEBUGREG_EFF_DB_DIRTY?
The problem is iiuc we always reload eff_db[] no matter which bit in
switch_db_regs is set, so this may still not clearly identify this bit from the
rest of the two bits...
Actually I think eff_db[] is a bit confusing here in that it can be either the
host specified dbreg values or the guest specified depends on the dynamic value
of KVM_GUESTDBG_USE_HW_BP.
I am thinking maybe it's clearer to have host_db[] and guest_db[], then only
until vmenter do we load either of them by:
if (KVM_GUESTDBG_USE_HW_BP)
load(host_db[]);
else
load(gueet_db[]);
Then each db[] will be very clear on what's the data is about. And we don't
need to check KVM_GUESTDBG_USE_HW_BP every time when accessing eff_db[].
>
> We have them in kvm-unit-tests for debug regs inside the guest, but no
> selftests covering KVM_SET_GUEST_DEBUG.
I see! Thanks,
--
Peter Xu
next prev parent reply other threads:[~2020-04-27 14:37 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
2020-04-24 20:59 ` Peter Xu
2020-04-25 7:48 ` Paolo Bonzini
2020-04-27 14:37 ` Peter Xu [this message]
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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