From nobody Fri Oct 10 14:02:03 2025 Received: from mail-vk1-f202.google.com (mail-vk1-f202.google.com [209.85.221.202]) (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 EBBFA25332E for ; Fri, 13 Jun 2025 20:23:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749846203; cv=none; b=SPH0VaBkF8ldJXjjN6YpaxkJ9TW3o+kut4ENoKkIv/OW1AtbKeirBF+DaRUO5OomYa0XksEjWyhTaasWeqop1yh35or3bJqTIAwNPFkSjWuykal/mZIyX4aNTuxcC1I21m2KwC5inlOlxoxQcmHepZcNS0emfs8eQGckyFRHfcg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749846203; c=relaxed/simple; bh=FO11FlBpcoyN0qJCLIRan7Jv37YU92XK6pL5bj0fOKs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Z35pOwDdreYXwCLGgkef1EdhWYhQqUT97MV+humhLGtvibQy0lPjRfDMKkSxjmGVXMVtgu9JMuVhJeZS8gWlEDv+aCUWkg820cKxklB6weJJvUkEUICdJVPlbLKfNMDeCB2FVxsXduwIsfQHYZDwzFh6MdrnR8lCjKLJPqlJRPc= 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=IKnkoOsR; arc=none smtp.client-ip=209.85.221.202 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="IKnkoOsR" Received: by mail-vk1-f202.google.com with SMTP id 71dfb90a1353d-52aa2e08ce5so2078707e0c.0 for ; Fri, 13 Jun 2025 13:23:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1749846201; x=1750451001; 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=tns2KslAWsQR/nPQ6ZJXfp49qOYXLA43OUirDZfOqnE=; b=IKnkoOsRW6EMTN6YX7I1JSmTbe0FRtYlOe9986lS/NopW5YO82wU+yfQCI1ZV4uDmZ LeCeJc8tSzXCjT6PKrK3WLTwUelJIaUR9I5AYugc0dwY6eZcPkMDG5YR4VEZ3sDzM0kI nlAYvifP5aIamgt1lTCY8qVpj6EPDCUTpQaXBkPDog4+jk4bMy+LVg9N+Fl2Hg6+inzK BWTht2kVqGdWtctanaXGa1juITOWQWMXwe2j1eGCIDzrBn2yhJMV/WdIGERC3/KmjGRE 7X0d9wKKcGEut+Uy8GzsNQ7eCMZO7Fyw2mqzaM0mbxwGutCljeyx3zsXUa3afGcSQfiJ fGtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749846201; x=1750451001; 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=tns2KslAWsQR/nPQ6ZJXfp49qOYXLA43OUirDZfOqnE=; b=nKjb13SGmm8YWLwxseJfaTl10Cq3p14z2oi/1X7xG/LvBbw0FoS0coqDzVkmH9N4sV Ji7jT08XMWQjW5d+rrBJMpaKpbhVH6wM1ycYl/4G6bXUs1VzmZIE7sOEVxx9svzKx/5Z crHH0KPfynRt05nKSLP8fDnv7nGlrY+vXcg6FEh01NB1a61RRp19CVADB0qxhR1eCw1s INKaGrga+Oq7lW8wuMVFxpYxzlCdXlOxC7TMmgn7aNoSKbAK9hJIePG268JwqlZ9d6wB FtC/IpUiXQcoR1Jd4P+l8LE1JOVbrnGyqNGK6oP8bdzPlHpZfLNeNnrjt2r0tsKMBrL9 ZmEA== X-Forwarded-Encrypted: i=1; AJvYcCVZZ1Ik3ZhEJsASje8U1hs72WMTibb6mAJXAI2m/YacKqfGLA2xd2AlljDTA+JPRhPxReQojIUoeFTfk/0=@vger.kernel.org X-Gm-Message-State: AOJu0Yx5qfYDc9g1Iinr9Ll2r8J+YT0jYLkSG/oBU9StPKBlR1mPyilq r7QC02DsyMuH+6p1DlD6U43NuMBVJKutmAWOcri9GrY+pm/6xZ+6E+iT0PkRSJseTUMqKsk9t4p mW6fUDiHIzruJO6kbhC18HQ== X-Google-Smtp-Source: AGHT+IE2AQx+r5mFnTFXsLCm8eJaB2E2MRY6faMF06zh29GE98yh28la0+/4aThtedtzqMsKaDbt81D+v6hsHfy2 X-Received: from vkbfs14.prod.google.com ([2002:a05:6122:3b8e:b0:52f:ecd3:a2fe]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6122:2789:b0:526:2210:5b68 with SMTP id 71dfb90a1353d-531494ba560mr1299111e0c.4.1749846200807; Fri, 13 Jun 2025 13:23:20 -0700 (PDT) Date: Fri, 13 Jun 2025 20:23:11 +0000 In-Reply-To: <20250613202315.2790592-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250613202315.2790592-1-jthoughton@google.com> X-Mailer: git-send-email 2.50.0.rc2.692.g299adb8693-goog Message-ID: <20250613202315.2790592-5-jthoughton@google.com> Subject: [PATCH v4 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 | 34 ++++++++++++++++++---------------- 1 file changed, 18 insertions(+), 16 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 10ba328b664d7..51df92973d574 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) + if (is_tdp) { 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) { if (is_tdp) @@ -7635,25 +7636,26 @@ 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) + if (is_tdp) { + 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(); - - if (is_tdp) + if (is_tdp) { + 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.rc2.692.g299adb8693-goog