From nobody Tue Oct 7 19:56:06 2025 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (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 EE75328C2DC for ; Mon, 7 Jul 2025 22:48:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751928514; cv=none; b=agM6YDj70teSPoPQNumHr8djSp/1OU/OGgBVUy9c3F6ldO4FnP7Gr12cNVUBa2L5Qtr3kJ9sQd5dJEWsBnQlWirAOM7LQYv959u8/MUyqT7zuM92EplATplmWWiSitrqewia6SFrZzaVdOoDK/yChVS+BqGI5yqktwWcOLH8cqE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751928514; c=relaxed/simple; bh=pfTbcdZSSLLL5oaShJwPnizP77bbCKnSgy4AHooKMXw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GnuLCkY+7sNNhBi3a5DftSOB7WQFmhleSMGrjBpta9dR8uuGkSvIqQMpOuxwCyUvaxXEBCz9CgXUarK/GMI0hEEOxTVXAd9PBItxBVcAjr4tMOCr/NWaFuOPNl2vNgN8pH4LI7PloY9waE8Q75mEbBsx2vPEGH1J9APQSYbgviQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=3qfKmOiM; arc=none smtp.client-ip=209.85.215.201 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--jthoughton.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="3qfKmOiM" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-b00e4358a34so2237606a12.0 for ; Mon, 07 Jul 2025 15:48:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1751928512; x=1752533312; 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=0XRp6vH5YCO0vNmv7C5suxuZF5x6t8xgiOL3MRTM9E0=; b=3qfKmOiMkBVsRMaycUR9uyhbT0BNP1dXEbPwwRtCCvkfAF5T/r1PqvXdO4FX15CS1S xKJ/8njqztT9nqAlmW6AUoxKFRFSyxL6vqBRFoLxqSCPDmeRYbRSmhKue8b+85RFuNNA HswpxEOMA6WpVc2vuDEvHQjjDR0xJNESMjEVKuFeCx/FCH5mCGEO0OxD3LQ519AZfueG UqgIavf4DCuU5iSsufa6T/Z6LC8/LJsPJnCTK5e6h7kZwTgpF3pCMoTMm2B0hrr//Ztz e7nhpmZsNskWfdsHDYmt5bgano1DkKRI8PHN/jnlKI40PSaz0bRjKw6P4dlQk0xgu1pd T7Sg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751928512; x=1752533312; 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=0XRp6vH5YCO0vNmv7C5suxuZF5x6t8xgiOL3MRTM9E0=; b=mQVGKF23Fyo1267QINGU96onGx1q7V6TPZumuJhTPtlhor9seoikmeDzjbI6goiM2K 32cZqWZFv/xGWNy2HDgGWYYWkBPLrX3AMHN6voY2E7eLAoHbetYaxm9HFSFK2tKTuRfX 7CnjbWLUtbwUPB2bRJVFHRoS8XOHAZmJa/DosbY+qrZBkTfaM9dtgZv3R/y05AIHOAB5 N/KdQd9VYA0b5MbVUlv3Ye/UZpdyinZsxRjAgnoomjXla1ZJlLEPhNK9RNf26Rx4kVCA oDSADsXFV7m3zKk0m52EieLNHHCTONb3RuPp4ThJ6AhUZOwLaOmzrZAVluU7MKXBXFCS VkMQ== X-Forwarded-Encrypted: i=1; AJvYcCV3QdUkU6XJLBSqDbIHxUI/65Ck8DOai5fS85+zRICExJvZYPuZ/QLqc9OGDVZg2EpFMDZ9NFypcbjRFrg=@vger.kernel.org X-Gm-Message-State: AOJu0Yz+FS97ey1Zjsa/zh0FNZDouErpgsMs0NMOL0gT1Urvt8Qgs+Av c1dcSswr5EwFw9P+PQHuxiQW4vz21NSbSLt0hB/4zcsO+ETpe+i60eeZ3Gp27zSDQNXj9H/h2AS dQu9TMq6/t5VDIkoNycr0Dw== X-Google-Smtp-Source: AGHT+IEQGLj1y5VPablO5Se2AW+glk11ncXO8Xt55xsvLAKmnnmI6ZkgDZYUUigN/e/HEzDXWEdb3qi16gZ1EFuY X-Received: from pjbqa14.prod.google.com ([2002:a17:90b:4fce:b0:312:14e5:174b]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:548b:b0:313:14b5:2538 with SMTP id 98e67ed59e1d1-31aaddfb84bmr21087259a91.35.1751928512116; Mon, 07 Jul 2025 15:48:32 -0700 (PDT) Date: Mon, 7 Jul 2025 22:47:17 +0000 In-Reply-To: <20250707224720.4016504-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250707224720.4016504-1-jthoughton@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250707224720.4016504-5-jthoughton@google.com> Subject: [PATCH v5 4/7] KVM: x86/mmu: Only grab RCU lock for nx hugepage recovery for TDP MMU From: James Houghton To: Paolo Bonzini , Sean Christopherson Cc: Vipin Sharma , David Matlack , James Houghton , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that we have separate paths for the TDP MMU, it is trivial to only grab rcu_read_lock() for the TDP MMU case. We do not need to grab it for the shadow MMU, as pages are not RCU-freed in that case. Signed-off-by: James Houghton --- arch/x86/kvm/mmu/mmu.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 7df1b4ead705b..c8f7dd747d524 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7577,17 +7577,18 @@ static void kvm_recover_nx_huge_pages(struct kvm *k= vm, nx_huge_pages =3D &kvm->arch.possible_nx_huge_pages[mmu_type].pages; =20 rcu_idx =3D srcu_read_lock(&kvm->srcu); - if (is_tdp_mmu) + if (is_tdp_mmu) { read_lock(&kvm->mmu_lock); - else + /* + * Zapping TDP MMU shadow pages, including the remote TLB flush, + * must be done under RCU protection, because the pages are + * freed via RCU callback. + */ + rcu_read_lock(); + } else { write_lock(&kvm->mmu_lock); + } =20 - /* - * Zapping TDP MMU shadow pages, including the remote TLB flush, must - * be done under RCU protection, because the pages are freed via RCU - * callback. - */ - rcu_read_lock(); =20 for ( ; to_zap; --to_zap) { #ifdef CONFIG_X86_64 @@ -7641,25 +7642,27 @@ static void kvm_recover_nx_huge_pages(struct kvm *k= vm, =20 if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) { kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); - rcu_read_unlock(); =20 - if (is_tdp_mmu) + if (is_tdp_mmu) { + rcu_read_unlock(); cond_resched_rwlock_read(&kvm->mmu_lock); - else + rcu_read_lock(); + } else { cond_resched_rwlock_write(&kvm->mmu_lock); + } =20 flush =3D false; - rcu_read_lock(); } } kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); =20 - rcu_read_unlock(); =20 - if (is_tdp_mmu) + if (is_tdp_mmu) { + rcu_read_unlock(); read_unlock(&kvm->mmu_lock); - else + } else { write_unlock(&kvm->mmu_lock); + } srcu_read_unlock(&kvm->srcu, rcu_idx); } =20 --=20 2.50.0.727.gbf7dc18ff4-goog