From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 738922EC560 for ; Fri, 20 Feb 2026 17:15:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771607732; cv=none; b=QdSvMwvst67UWqH7gKM4ETdGEbnueMzaCG4ciFHX7pidoJ+0rhlc0S8f2OjAEdEflWs8jsh6snXp9z4s/4IfSzO4i6aHxJnphSP1qMoo+K+7pqdpk9rcCZlgNbQYIEQWnmWeNX44xbcYL+kmwlXJd7dT+sG/GRl0mgyMvOAcKS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771607732; c=relaxed/simple; bh=xh1l3uM68eCJR2SH6gaUCO0N9alFSIukiARRMNTDClo=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ciGRd4E6iovM6C+vp1hrbBwkx2Z97SPbXnLbisR/SSloXRQpSo4vYSbWYcnWsBqp5Agjyo4ZZuDzMZzad09t2ho5RLc4GpPfraTo1OBFes4L19PNytOYgf3wVLMzeuIU3cQPHsdcn6+MsaXrOXUtqXZnJDddV/jYQbQRcizPDCw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MusjWFB4; arc=none smtp.client-ip=209.85.216.74 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MusjWFB4" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-35626b11c51so1730600a91.1 for ; Fri, 20 Feb 2026 09:15:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1771607731; x=1772212531; 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=vXPc2TVPq9CrPzaqQARpE12B7qXqTUkpOVKjyqscmPY=; b=MusjWFB4S8JahUL5FvU543fZbIRz953ZP9q9enMGFyz6/rcGjvud3CGJNRcc102tr7 8UDaDhAIcmfn3ghT57olGwLz0Ruvj9VFCiW0ZJsnCw9M2CwKYZC7mzhWIoEckS8nvjc4 mMihEBg/tkhBIaCBRcwDxOkaDCReJsAty6GXViioyVc7LVQpGzNKY1HuHeKA5VnBGFUN h3JFc2CfG1P0HZaVsnR8iwUw7s9jUUzjBCXkeNd/v3kP0/bbkTaCobCLQl4CmsG1bdi+ JDDEcixo2mPrbHhASRrZ6gLjihsRSKVvgJz1TAIAa+fmEto7Tn5bpFCiZunqZbHUDWOC rnTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771607731; x=1772212531; 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=vXPc2TVPq9CrPzaqQARpE12B7qXqTUkpOVKjyqscmPY=; b=I6+e8cPOi2UFMBY67SvR83gYiKG7SQSRQ0bXpH+5meeugDdQuj0wJ1YEKbiUqCp9g7 c91tZ1DbTdGLnS/DxNsLX1w/Q/q5qBEqEY2yDw5qpETkTJPjhQaxYkiBXiBhOpnGwecG lbhaxQlvtJH7fxtPdOVd2PKsMfaDN347JDXTRZgUGkhdSK9nX9aVOyFH+WED95uxO3LN syHMIe2YIwTYr8IlK19J4oN4VGByPu+odfeUAluhs50bU3PX7OjWkMrT2J1dvtUh4oaI CshPpQstCD5hZj8WNR3cu2KHWVBRpMl7YuBAZzDRPWYdURdP08tlWvKHM6EQ5ySK/vP8 09Sw== X-Forwarded-Encrypted: i=1; AJvYcCWjnNcfMfwpmGelYtfOfgLJFKv+Kq4riCtIqY4LfZOtQTmqGvrGWDE0qERJmX+AZrO3nIWI/Uz8PAPDl4M=@vger.kernel.org X-Gm-Message-State: AOJu0Yw8N2CIx/yUiKC2N1UaRN2+CfcgrqGAyM4RSH377t1B2n9h69E3 18duvbHuCxe5P6pb/SrKx9Xu2XsOgZogAfuDS04iBFGuyR9M7KVZ+7fHCPWhaY3re4rFUtyBy/u CE5Dl7g== X-Received: from pjbmq13.prod.google.com ([2002:a17:90b:380d:b0:34a:c87f:a95a]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1f84:b0:341:8b2b:43c with SMTP id 98e67ed59e1d1-358ae8a4366mr402595a91.18.1771607730730; Fri, 20 Feb 2026 09:15:30 -0800 (PST) Date: Fri, 20 Feb 2026 09:15:28 -0800 In-Reply-To: <20260210072530.918038-1-lsahn@ooseel.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260210072530.918038-1-lsahn@ooseel.net> Message-ID: Subject: Re: [PATCH v1] KVM: Use memdup_user instead of kernel stack to allocate kvm_guest_debug From: Sean Christopherson To: Leesoo Ahn Cc: Paolo Bonzini , "open list:KERNEL VIRTUAL MACHINE (KVM)" , open list Content-Type: text/plain; charset="us-ascii" On Tue, Feb 10, 2026, Leesoo Ahn wrote: > Switch to using memdup_user to allocate its memory because the size of > kvm_guest_debug is over 512 bytes on Arm64 and is burdened allocation > from kernel stack. 520 bytes is a lot, but it's not _that_ much, especially since kvm_arch_vcpu_ioctl_set_guest_debug() is leaf function (ignoring tracing). Is there an actual problem on arm64? I.e. does this one particular allocation lead to stack overflows that otherwise don't happen in KVM?