From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/10] KVM: x86: Make kvm_x86_ops' {g,s}et_dr6() hooks optional
Date: Mon, 4 May 2020 15:19:26 +0200 [thread overview]
Message-ID: <37a30f26-2561-aada-9bdc-7bc9cddf0d7f@redhat.com> (raw)
In-Reply-To: <20200502043234.12481-4-sean.j.christopherson@intel.com>
On 02/05/20 06:32, Sean Christopherson wrote:
> Make get_dr6() and set_dr6() optional and drop the VMX implementations,
> which are for all intents and purposes nops. This avoids a retpoline on
> VMX when reading/writing DR6, at minimal cost (~1 uop) to SVM.
Can't get_dr6 be killed off completely here, since vcpu->arch.dr6 is the
only value that is ever passed to set_dr6? OTOH no complaint about
adding the if for vmx_set_dr6, since that will also be covered nicely by
DEFINE_STATIC_COND_CALL.
Paolo
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 11 -----------
> arch/x86/kvm/x86.c | 6 ++++--
> 2 files changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index de18cd386bb1..e157bdc218ea 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5008,15 +5008,6 @@ static int handle_dr(struct kvm_vcpu *vcpu)
> return kvm_skip_emulated_instruction(vcpu);
> }
>
> -static u64 vmx_get_dr6(struct kvm_vcpu *vcpu)
> -{
> - return vcpu->arch.dr6;
> -}
> -
> -static void vmx_set_dr6(struct kvm_vcpu *vcpu, unsigned long val)
> -{
> -}
> -
> static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
> {
> get_debugreg(vcpu->arch.db[0], 0);
> @@ -7799,8 +7790,6 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
> .set_idt = vmx_set_idt,
> .get_gdt = vmx_get_gdt,
> .set_gdt = vmx_set_gdt,
> - .get_dr6 = vmx_get_dr6,
> - .set_dr6 = vmx_set_dr6,
> .set_dr7 = vmx_set_dr7,
> .sync_dirty_debug_regs = vmx_sync_dirty_debug_regs,
> .cache_reg = vmx_cache_reg,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8ec356ac1e6e..eccbfcb6a4e5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1069,7 +1069,8 @@ static void kvm_update_dr0123(struct kvm_vcpu *vcpu)
>
> static void kvm_update_dr6(struct kvm_vcpu *vcpu)
> {
> - if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
> + if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) &&
> + kvm_x86_ops.set_dr6)
> kvm_x86_ops.set_dr6(vcpu, vcpu->arch.dr6);
> }
>
> @@ -1148,7 +1149,8 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
> case 4:
> /* fall through */
> case 6:
> - if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
> + if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) ||
> + !kvm_x86_ops.get_dr6)
> *val = vcpu->arch.dr6;
> else
> *val = kvm_x86_ops.get_dr6(vcpu);
>
next prev parent reply other threads:[~2020-05-04 13:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-02 4:32 [PATCH 00/10] KVM: x86: Misc anti-retpoline optimizations Sean Christopherson
2020-05-02 4:32 ` [PATCH 01/10] KVM: x86: Save L1 TSC offset in 'struct kvm_vcpu_arch' Sean Christopherson
2020-05-02 4:32 ` [PATCH 02/10] KVM: nVMX: Unconditionally validate CR3 during nested transitions Sean Christopherson
2020-05-02 4:32 ` [PATCH 03/10] KVM: x86: Make kvm_x86_ops' {g,s}et_dr6() hooks optional Sean Christopherson
2020-05-04 13:19 ` Paolo Bonzini [this message]
2020-05-02 4:32 ` [PATCH 04/10] KVM: x86: Split guts of kvm_update_dr7() to separate helper Sean Christopherson
2020-05-02 4:32 ` [PATCH 05/10] KVM: nVMX: Avoid retpoline when writing DR7 during nested transitions Sean Christopherson
2020-05-02 4:32 ` [PATCH 06/10] KVM: VMX: Add proper cache tracking for CR4 Sean Christopherson
2020-05-02 4:32 ` [PATCH 07/10] KVM: VMX: Add proper cache tracking for CR0 Sean Christopherson
2020-05-02 4:32 ` [PATCH 08/10] KVM: VMX: Add anti-retpoline accessors for RIP and RSP Sean Christopherson
2020-05-02 4:32 ` [PATCH 09/10] KVM: VMX: Move nested EPT out of kvm_x86_ops.get_tdp_level() hook Sean Christopherson
2020-05-02 4:32 ` [PATCH 10/10] KVM: x86/mmu: Capture TDP level when updating CPUID Sean Christopherson
2020-05-04 13:25 ` [PATCH 00/10] KVM: x86: Misc anti-retpoline optimizations Paolo Bonzini
2020-05-04 15:09 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=37a30f26-2561-aada-9bdc-7bc9cddf0d7f@redhat.com \
--to=pbonzini@redhat.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sean.j.christopherson@intel.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®