From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2E1B81741 for ; Tue, 15 Apr 2025 01:05:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744679152; cv=none; b=gEe10XJh7ZdzahwT4PD3CpkQQypeDbNm9NV0D6x8J/KsWneG6OzbVXiEpQe2r6L4/fcZQsomFNftqEIEgJLGpAD90vtK++xjVtPISoyekfXjx/GGKLekXN/PVkWYFV8kZI9SOmScGanrZU1UzKOkQulsOQHOOSPDDJ+Sx2quhaI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744679152; c=relaxed/simple; bh=kmQ6eBY4CNUxjNfOexNgsrdDcNzfRZcNC8pQ2YAlb2w=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=bYgrYAaLQKPlYWV0w7mLWK8IpJBQaKxuV2VmLH1Lt83cdFOE4N9+LD0auPYuiEq2QbpUQv8ZmF2jktFbNeloCJ1+F0+TCAWDyAt7kCOa0d4q+Bk8V9RD6STUtCZVOMlRyTHeSznW3EG00s5vDCM4cD3n/JxhNbilUitYPYnCmv8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=QUJr4LSG; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QUJr4LSG" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-227a8cdd272so41248455ad.2 for ; Mon, 14 Apr 2025 18:05:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1744679150; x=1745283950; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=tE1adoT0PMRc2ZI2MNLpe+tvwhjFP5aL0rCGtHCJJ4w=; b=QUJr4LSGk10u+0oDlGbHHJyX4pZWGohqi7sxarvh7/EqZQIzgBMEDYMxQX0M9HnFwe 5eE017nQn01wJKEmjeTB6wlfZAoNhTgfoRzqZpG+a6ysfkjCR2DaO/O+lmDh+dPhoB5f 7SFxcGCTzOma89h5PgrDnMZyC1zPFBSqXXP60u+X0nDSjF5Frmfm+EJFQHk+JGWMPiHs ACZSMgWP/Rpq7lXf/XOlBd4bAfGSOQZPsCQe/qTM711O/rEqAPudhhtTcMx2GYomI5bz DK81VuZxklBthmHFQLC255ZXDnW9Mc3DQOySomCOGlKRhs+i4oh3HLk7GJIBVgZqCK2O 4tVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744679150; x=1745283950; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tE1adoT0PMRc2ZI2MNLpe+tvwhjFP5aL0rCGtHCJJ4w=; b=lRkKb2A9laXZOOFIEnQ6tdTe44IxXp8pqNla1EsXX+11cDIFNszpTY6tp5fzMB/3Yt ISS6ZALploifYk+xk6nFAYNgZU+QMRABWVEl8kSMckUHM6Nk3PLj5IZC2fHa/R4pmdN2 /KjDSQ2fkuufJEI/f0I22Q6rrsHtZn1B+5v/aBh4/N9PHPCArHOpu1l4T/B6yLIN2Wa5 O7mIugpWZ2AUGZdjNh787B+TH7jLICWBjSu5q7RH2dXQW01PnLWS19x8bk7s68CnEHhu wDMOTNeyXRqWYvnrzy0J7Woli1mNpsTprxk0S285hsAYZLzr6cFNTWLKrmJGiEbZNb50 rn1Q== X-Gm-Message-State: AOJu0YymUJPfc3uLM82I3CxJrbRlcWCMaalC1fghPE+8JVvz2tem+DMf sKBMZpQADuOqiv0Q3waEhb33g4kRtuiQ9ZDnkIuzPNEv1JrVbjXHI0+SHI0liwbv4ssk9uGGfRH GhQ== X-Google-Smtp-Source: AGHT+IFbFP3u+rs3c8JoY3Z9h6FkMSEmt0p/0gguW8s8qvS+PwTJMpqhnW2RNbzoz4XXWA0j7ScY9/Ze8c8= X-Received: from plrb10.prod.google.com ([2002:a17:902:a9ca:b0:223:f7e6:116d]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:cec4:b0:224:e33:889b with SMTP id d9443c01a7336-22bea4ade03mr221654375ad.12.1744679150211; Mon, 14 Apr 2025 18:05:50 -0700 (PDT) Date: Mon, 14 Apr 2025 18:05:49 -0700 In-Reply-To: <20250414081131.97374-2-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250414081131.97374-1-ubizjak@gmail.com> <20250414081131.97374-2-ubizjak@gmail.com> Message-ID: Subject: Re: [PATCH 2/2] KVM: VMX: Use LEAVE in vmx_do_interrupt_irqoff() From: Sean Christopherson To: Uros Bizjak Cc: kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Content-Type: text/plain; charset="us-ascii" On Mon, Apr 14, 2025, Uros Bizjak wrote: > Micro-optimize vmx_do_interrupt_irqoff() by substituting > MOV %RBP,%RSP; POP %RBP instruction sequence with equivalent > LEAVE instruction. GCC compiler does this by default for > a generic tuning and for all modern processors: Out of curisoity, is LEAVE actually a performance win, or is the benefit essentially just the few code bytes saves? > DEF_TUNE (X86_TUNE_USE_LEAVE, "use_leave", > m_386 | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE | m_ZHAOXIN > | m_TREMONT | m_CORE_HYBRID | m_CORE_ATOM | m_GENERIC) > > The new code also saves a couple of bytes, from: > > 27: 48 89 ec mov %rbp,%rsp > 2a: 5d pop %rbp > > to: > > 27: c9 leave > > No functional change intended. > > Signed-off-by: Uros Bizjak > Cc: Sean Christopherson > Cc: Paolo Bonzini > Cc: Vitaly Kuznetsov > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: Dave Hansen > Cc: "H. Peter Anvin" > --- > arch/x86/kvm/vmx/vmenter.S | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S > index f6986dee6f8c..0a6cf5bff2aa 100644 > --- a/arch/x86/kvm/vmx/vmenter.S > +++ b/arch/x86/kvm/vmx/vmenter.S > @@ -59,8 +59,7 @@ > * without the explicit restore, thinks the stack is getting walloped. > * Using an unwind hint is problematic due to x86-64's dynamic alignment. > */ > - mov %_ASM_BP, %_ASM_SP > - pop %_ASM_BP > + leave > RET > .endm > > -- > 2.49.0 >