From nobody Fri Jul 24 05:21:21 2026 Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) (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 11CC036606B for ; Thu, 23 Jul 2026 16:20:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.71 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784823621; cv=none; b=rC5h2peEkBgAvt8XX6e3OaY3IlhidWNOYoSSl0KKum8TncmHBgbH13HpUjMfcuyEmvNQ9MenXUxff42N/lyC+m4Phoyx5tp2z1UHrIgDpIkK5cHiBNnHu1tueopdS18JQ08+ME5vIMaZSgE2m2ddxAXPh9rH+7BtOWcZVbRXdNQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784823621; c=relaxed/simple; bh=wjwRwP+aVnxjJIJeqwg1P5oX2bJlhP2+1TFOJTHitgs=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=dVrnWRO+2QqbrFLMq/JqdTs42XjsLzPiq/O8o4zEEWGmUMaR/JhoapZ81b2S3A3hr7ROHjCY6bY9E6BrqAwX5RyA+/2j/hR6tLZ6BcTfeaT/+d6D9zDWw5dtCGD3x2IgdUQwwm1z45tVtvJw32Kvh6E1I8mGNpD2y4ZzxZTEl8c= 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=nanRNQue; arc=none smtp.client-ip=209.85.128.71 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="nanRNQue" Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-49561facb1dso7282005e9.3 for ; Thu, 23 Jul 2026 09:20:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784823613; x=1785428413; 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=8fLZBrc7U0OaH9gD4/eAb175qJMFqjKMfWGNNQ6QKQA=; b=nanRNQueGDs2+/DwYQNiZRwGzJywmpXJ7/H23YT6OuvVp7aKiDH2UQfi7s6LtuXLYj ia9Z7ZEa3q34yhyIjbK+cZrMuEuIuVzk8T5yy3esbryktTwvGGQuFr7FA2KZcCSYZyTS 6eI8Nui4BBhXVnebeAsK+h4dm1KmQhz7IogPCj7hn3ku3cYANpDsU1m3vhH+68q/QY53 Re9+b9oofhEU7dK5ewjf1v2PD0o7z01OvFRg/CjhTbJGrlqta0vShne8NA6QZk0meutn yE5NaAiMzTUjP03y0qOpoX/+gUjy914Z5Os1VHu/GobM46ybbHQHZFqkbjGBOpLIHZEH 4ExA== 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=sjTYpKbusGcI7vUAUxjbn5X1fg1oliWi95eiplYBLZIIZDwK3VXqoINZZkXml/I1rG erQsUTf5nBhkqct2gGAXJNy5Ez+wMMtIavBZ3z8LZmU8z77rIysbqE9S2FA7G5NQY2UA U3rDt+EqRHYFU9n7eGaQmsLzHEpunFC8OCgnmXKlPiOLB6h53Mvwip8ut08B6wbOEBax MnPIZr3kClY/egwCwlz3lgn9iBuODriE4Wqhr734Q5D63NkE/N6F/1BbpU9zYESBNwAQ YIdYUPCFw+0gkDWOMnGa5Qqi/FyN0SEcFBfoUqacJvEFLhZgRD6xq5ZMrYXmML3QSIcR rFOQ== X-Gm-Message-State: AOJu0YxUhnGpWDMPkcsb806ERTsvbLhO/Cg8fysjyp/CDhWLwRpHaX0m 9EE25g3ntFBJX7Xwmok7C9RxPlHAjKFRiFFXYFQhviYiSB1nKm8IRai/DWQYuRXkUTIKHC5vLYo 7L7C0vvHxBv4Gu5JMtHfk75u8Tk27tDmxqpkLNHr4rqUfuuLCkiVe2BGgFjgAbbH+FcKmXbL0AW YtdYX+MvjMMaWMG6kW7zx2BZNEj0ilBGjAKDRKxjKG9vR3Udc6TAFQivQ= 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: 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: <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-Transfer-Encoding: quoted-printable 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 Reviewed-by: Fuad Tabba --- 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/nvh= e/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, =20 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); } =20 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); } =20 --=20 2.55.0.229.g6434b31f56-goog