From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (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 A7FC83C9EE5 for ; Mon, 20 Jul 2026 20:35:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.69 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784579736; cv=none; b=TAY3WV09rnTLOohsuN20BJ80/HI2jNnEQsPR3odxvn4y+MnRopVFpVoSdba4lAAf0DNm0hJNQUqAZUinqWwVyXi2HrBQqSo8oJWVph/DlattZw+BnIYacbeM7XCRgTd3/qDbNCYNeaznqD+IHteXVT4ukpf3K5G8RMvUHOSYq8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784579736; c=relaxed/simple; bh=AEIRTgpv3KiZzLgCI7Rlc0YF+p0PrirI6dYHcC7ObJI=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=tzlBQvGUIIeE7vA/6SC187H5D9rTEq8SsjN4kLVs6vmK6glJauRySIzmZLdVToLSR3fNATJadLxPbaGhlP50Cq7xwIl5o3C7tBNADUjx5bIQEqGhDFTc0xZki+NiclBdymXoEy91jUh5TAX/gMDRTnxZXWksvXpvCToBD8ONuKE= 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=KBRH+qLu; arc=none smtp.client-ip=209.85.221.69 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="KBRH+qLu" Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-473ac08a6a4so6705277f8f.0 for ; Mon, 20 Jul 2026 13:35:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784579733; x=1785184533; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=LA6BVqbIhEwIMVMXHgwJu8nqjN0TgDEofdIQtGf4DJQ=; b=KBRH+qLu2HZvysY+II+ltco2S+Pin7Oc6jkYSDQSU1ca5o5kbGMJrn4Qv2RmZ6keRo /rVFkzWdskONK1Fttg/PtrE1jSZBg0qrSz8IGclSaV4EL9v72wgL+zon4pdYeE/8kZ1w U21bRp+t2OZZJ/+4LAOkOBCKMnvwllkJ33j4+RVkzOHGtizhnTxW0NV5PEx+I6m++Xx6 QwpMsSxs8PiCpT/bChmExIrRJSRR+/pHYlGwXy9gtmQUsJpofiXNVdOxHVu5cnRg5H12 cCOclV8HDaaESNmWx0WH9T93JpSEtFPBzOekr2vU+WqB3T1NjLA3U9QgA0H0AnCmzEl5 LbqQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784579733; x=1785184533; 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=LA6BVqbIhEwIMVMXHgwJu8nqjN0TgDEofdIQtGf4DJQ=; b=q5JeWHruq8fdiE0Wd/WG3WTCCK9ZOgTOdZmATMIXwwTxiVHD5bVF19Hd4ECcfwbl+p vUfWkCVkDZhuEQUelgKyF4E6AjYBSh+eE5erdS5nOCAAiqRUIXqfc2TNzQqv42IEVxJP LiZ9TuIq9zDYaZPmf/2XyiP57O5klVMllPhAsXHvYdUmfZ/fQwoUAS3eW0QecbRYU8kg a+B6cO8NmYh2UIkVsd1yEofi0mTGBUWzJkjmH7pzErn5zCjDu+rGk5cwNDxPcVB6v5Vb qDwCFdbTV49p7DxN2gxhv5GQ2jJMszzF0a7J3Zm0NwfWrHcjbOA9TYefDcI4qbyIT/O/ Djtw== X-Gm-Message-State: AOJu0Yw4biRoqBwXf+3cS4Kda7id/YpYSZG4hIpY1XGSgHEs3TLpv/EQ crHqLYtzEMF1pk/UJ5oEA0aJO72BqlJ9MRcA1y0uBTBMH6zT5z8jOE/k0g9wCxAiJ6RKlJbwX7H kkgXL3zOHx/oMxsMsbtUyWzfbQhazjBX3wyL9VcWwWqvFBp2V6lqGng/8+9kM1hcofpiwOxzHu/ KZS8JDwjzP7GqgvR/lCAfubEYLNgn397FZGpuNFV/iWT+il2G2879S6D0= X-Received: from wmpi31.prod.google.com ([2002:a05:600c:4b1f:b0:489:1b01:386f]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:310e:b0:495:52dc:73a1 with SMTP id 5b1f17b1804b1-49552dc776bmr119110015e9.29.1784579732667; Mon, 20 Jul 2026 13:35:32 -0700 (PDT) Date: Mon, 20 Jul 2026 20:35:29 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog Message-ID: <20260720203529.1276355-1-smostafa@google.com> Subject: [PATCH] KVM: arm64: Optimize protected mode and FWB 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. Signed-off-by: Mostafa Saleh --- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 4e329e39a695..6e9229106a25 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -261,6 +261,10 @@ static void __apply_guest_page(void *va, size_t size, static void clean_dcache_guest_page(void *va, size_t size) { + /* See __clean_dcache_guest_page() */ + if (cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) + return; + __apply_guest_page(va, size, __clean_dcache_guest_page); } -- 2.55.0.229.g6434b31f56-goog