From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (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 DC9D547A861 for ; Thu, 23 Jul 2026 16:20:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784823625; cv=none; b=B2WZMuClaw6lZ2xa56jLj762AFtDJWeqmBDZyBoQz9WIlDYPmViA0qhSb82CXNzPWdqv/P5gX6ssp0FsKqAQf3I4xXsjjVB8sBd3/PRnZof5IFglb64lrIRblKMToWtN7UseQaguZj43pOm8/OO5JQ9NF7FOhjdI0FyCcAn623Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784823625; c=relaxed/simple; bh=wjwRwP+aVnxjJIJeqwg1P5oX2bJlhP2+1TFOJTHitgs=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=vEUgatmiRjbLY4m0PaOp4Ga8790ntEL89BcLfS93PsgIV5qYaw5K4WyHCSTla4lBEAU5YjBgHiUVCZkVgqTT42VRM86HjIIAXt6mJKTdKhkW0nS7lXgsegvbn+US56f6rRPPb/Dbs/3V/7S9+/wlrzvaju51Ejv+3xWLu4v1Unk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--smostafa.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=HgPN2BS8; arc=none smtp.client-ip=209.85.221.72 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--smostafa.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="HgPN2BS8" Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-47f753a0aa0so476198f8f.3 for ; Thu, 23 Jul 2026 09:20:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784823613; x=1785428413; darn=lists.linux.dev; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=8fLZBrc7U0OaH9gD4/eAb175qJMFqjKMfWGNNQ6QKQA=; b=HgPN2BS8l20ht4PfBGzSNOc0sXSoU1lJDBQM91BsAa/ncnwUAA3jYrxfIkMCB6shiT NrWs7QRf01WapZDFB2Wkyd9BvQt42Ei8dn3NFV5k4Pl4NWrRDaS6Yh6OGuItEDFiaOqc uutyFko8Yix0wRmaXStf/S4xVCvdnmRi3Fk/vDiNiG/LUWxKOqPXzgiiRMkiJTee+maQ Uu5qEzxdTZdFBw7mfab2NTlg/zgrnryXzUXzTFHc3IC4Nf85V1bxdKeRLCvJCKSNmW54 sztUtOQBGtbj7FU1CMBFdl7sJwRNVOoAxKd64qUp8EH853ShSXIs8Wm63ckIw5O+i4ub zCHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784823613; x=1785428413; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=8fLZBrc7U0OaH9gD4/eAb175qJMFqjKMfWGNNQ6QKQA=; b=N5vPxquLwEAtBpJmlPqz6neUHoEioj7E48XfABEpr9Q3q6hIGXeZzpJRBUQBni0MTK vyDE5xTbvDCj2q4+V85mAcM94On3ym5b2nsBbFwjv4idIxNCNDjEtXEnh3GLfdeYeXcU r2YPSKKeu48x1tAejJHZ91ce/K2saPljXy+JdVSs907Cx1ENAcwERtRxUZbAxK9NbOQv kKozFlK4gcKty3YpjBhZtQ9CpIzZZliDZjtwL99JhJlLA0YETEF3fMRIoMm44Dd9MsXV d8SqDGVkjijHQSu27fjq94UnZZtqn0eBJ/VUdS2T8F1b40SjtDNq08nMIix6uD5tESyd TrRA== X-Forwarded-Encrypted: i=1; AHgh+RqIGCI6sTfqPL0BMNUBlrUS5jhN2WOJNlSevtQR2P1KTO5Or8b/lWac+K4HsQ11iPW4slYt0N0=@lists.linux.dev X-Gm-Message-State: AOJu0Yz5f1NvNCq1muHY7pDh3gBXugoz7gcrkz3zwPiUgZ1k89ukt4RJ gs8JEebec86NTFjjU4uOWbhGAIsnfjSg9r0qIWYt4L3jMbwo+idRjjI1dJdSfOs8cujQybcj0L0 P5x7hkAhV5VLbJw== X-Received: from wmnq10.prod.google.com ([2002:a05:600c:2eca:b0:495:5b4a:53f1]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4685:b0:495:63e4:3a91 with SMTP id 5b1f17b1804b1-49573d132f3mr42321645e9.35.1784823612359; Thu, 23 Jul 2026 09:20:12 -0700 (PDT) Date: Thu, 23 Jul 2026 16:20:02 +0000 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog Message-ID: <20260723162002.3848054-1-smostafa@google.com> Subject: [PATCH v3] KVM: arm64: Optimize protected mode with FWB and DIC From: Mostafa Saleh To: linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: maz@kernel.org, oupton@kernel.org, seiden@linux.ibm.com, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, vdonnefort@google.com, tabba@google.com, sebastianene@google.com, keirf@google.com, Mostafa Saleh Content-Type: text/plain; charset="UTF-8" KVM opportunistically enables FWB if supported by the system for guest VMs, which allows it to elude cache maintenance for data as they are forced to be cacheable from stage-2. In that case, __clean_dcache_guest_page() will immediately return. However in protected mode, before calling __clean_dcache_guest_page() it loops over the range and fix_map/unmap it, issuing TLB invalidations, dsb() and isb() unnecessarily. This can be optimized by returning early if FWB is supported, kvm_pgtable_stage2_map() already issues dsb() and tlb invalidation functions issue dsb() for the unmap path. Similarly for DIC, we can omit the call in invalidate_icache_guest_page() No isb() needed as ERET is context synchronization event. Signed-off-by: Mostafa Saleh --- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 4e329e39a695..39aa8911f62c 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -261,11 +261,18 @@ static void __apply_guest_page(void *va, size_t size, static void clean_dcache_guest_page(void *va, size_t size) { + /* See comment in __clean_dcache_guest_page() */ + if (cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) + return; + __apply_guest_page(va, size, __clean_dcache_guest_page); } static void invalidate_icache_guest_page(void *va, size_t size) { + if (alternative_has_cap_unlikely(ARM64_HAS_CACHE_DIC)) + return; + __apply_guest_page(va, size, __invalidate_icache_guest_page); } -- 2.55.0.229.g6434b31f56-goog