From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: 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: Thu, 23 Apr 2020 12:09:42 -0700 [thread overview]
Message-ID: <20200423190941.GN17824@linux.intel.com> (raw)
In-Reply-To: <20200416101509.73526-2-xiaoyao.li@intel.com>
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
> };
>
> struct kvm_mtrr_range {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index de77bc9bd0d7..cce926658d10 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1067,7 +1067,7 @@ static void kvm_update_dr0123(struct kvm_vcpu *vcpu)
> if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) {
> for (i = 0; i < KVM_NR_DB_REGS; i++)
> vcpu->arch.eff_db[i] = vcpu->arch.db[i];
> - vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD;
> + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_NEED_RELOAD;
> }
> }
>
> @@ -8407,7 +8407,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> set_debugreg(vcpu->arch.eff_db[2], 2);
> set_debugreg(vcpu->arch.eff_db[3], 3);
> set_debugreg(vcpu->arch.dr6, 6);
> - vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD;
> + vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_NEED_RELOAD;
> }
>
> kvm_x86_ops.run(vcpu);
> @@ -8424,7 +8424,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> kvm_update_dr0123(vcpu);
> kvm_update_dr6(vcpu);
> kvm_update_dr7(vcpu);
> - vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD;
> + vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_NEED_RELOAD;
This is the path that I think would really benefit from DIRTY, it took me
several reads to catch that kvm_update_dr0123() will set RELOAD.
> }
>
> /*
> --
> 2.20.1
>
next prev parent reply other threads:[~2020-04-23 19:09 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 [this message]
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
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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