From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AAFC23D75A1 for ; Tue, 2 Jun 2026 10:11:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.21 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780395074; cv=none; b=d+n0S5DJMEBbgHRFR/fET638bZPedFzfH2B5PVqG0EycpFt/wJlYGA+qp8Rc4cjZ+3jql63/8IjF7Sog2zbBSWGc8cT7MA6COgwhU3NMMLmrUPSwH3J9b3kfnry+THxvDR6gCi1ftVWEPjZJINZcmdaRQ5dqyRY1635ZG7mhLws= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780395074; c=relaxed/simple; bh=4HHmcNcFiFlZfxsZJ4yS1AIHeBQqoP6l/x/Fk6ajWso=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Kxw0w0QL3twrdmjmCJaF4PFirk447itJvBMd9qs18MFHGBVUsBSU1BobhUqgX20WqJ/j+QV+e7FG5/T0wzLKyw0Qux6cYrMcWwjIzJ9kaZpLo4fUXHQ+fkU5dUzbxhpZEgygM0yJA3nZP4fM1AxXFs8POu3C5OHFNfnIOW7zj2g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=CMi5k5jK; arc=none smtp.client-ip=198.175.65.21 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="CMi5k5jK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1780395074; x=1811931074; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=4HHmcNcFiFlZfxsZJ4yS1AIHeBQqoP6l/x/Fk6ajWso=; b=CMi5k5jKyvNKmVD+dZF+5Pm5BYR2gVNypzSjaRdGIeeB13TcLUgqsjeg s0esYetUEg3Cia0Ae77zeGIBXpNRtJOr5vUPEf3Zkm1ar/S4J94827zsn 795GZRtCsIEE1DsenU55lM4jdS68hNt4yAfrvfbZWbyFXNuWK/hyl8fCY l7Dl3tzS1QiUHBMYjI+Xbc1RFmQdA+z0z8OMyiDiFUeBMvynJjLWmCFa+ IgfclN+iqvQjvc7syyNDNS3FNU3TBh9FPUMDCYw4g9BG138pnHYFO/9dY Quhbz94sJvp1cWsdo37UUZ+SOiPWoDBxlX0QTWyKIoEYKnWeHGetlErA0 Q==; X-CSE-ConnectionGUID: fGPnwh/OQHWBTuoRHauf8A== X-CSE-MsgGUID: mIBNoJJYSFyWudnGSHywhA== X-IronPort-AV: E=McAfee;i="6800,10657,11804"; a="81076790" X-IronPort-AV: E=Sophos;i="6.24,183,1774335600"; d="scan'208";a="81076790" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jun 2026 03:11:13 -0700 X-CSE-ConnectionGUID: cT7ZUV4pTFG2fHINoQIefA== X-CSE-MsgGUID: UV2Pi1QmQymaAB8n3+1zHA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,183,1774335600"; d="scan'208";a="243701388" Received: from unknown (HELO [10.238.2.24]) ([10.238.2.24]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jun 2026 03:11:11 -0700 Message-ID: Date: Tue, 2 Jun 2026 18:11:08 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [kvm-unit-tests PATCH v2] x86/lam: Allocate test page from AREA_LOW instead of AREA_NORMAL To: yexun Cc: kvm@vger.kernel.org, chao.gao@intel.com, seanjc@google.com, pbonzini@redhat.com References: <20260602060116.35206-1-yexun@linux.alibaba.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260602060116.35206-1-yexun@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/2/2026 2:01 PM, yexun wrote: > The lam test does not set a guest memory size in x86/unittests.cfg, so > QEMU falls back to the default of 128 MiB. AREA_NORMAL starts at PFN > BIT(36-12), i.e. physical 64 GiB, which is never initialized in a > 128 MiB guest. As a result, alloc_pages_flags(0, AREA_NORMAL) returns > NULL and test_lam_user() ends up running its LAM checks against a NULL > pointer, which is semantically meaningless even if the metadata-bit > arithmetic happens to succeed. > > Allocate from AREA_LOW instead. AREA_LOW_PFN is BIT(24-12) (16 MiB), > well within a 128 MiB guest, and bits 63..47 of the resulting linear > address are still zero, so the LAM48/LAM57 metadata-bit checks remain > valid. Update the adjacent comment accordingly. > > Fixes: 0164d7595c85 ("x86: Add test cases for LAM_{U48,U57}") > Signed-off-by: yexun Reviewed-by: Binbin Wu > --- > v2: assert vaddr instead of pfn > v1: https://lore.kernel.org/all/20260601035401.39303-1-yexun@linux.alibaba.com/ > > x86/lam.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/x86/lam.c b/x86/lam.c > index 87efc5dd..33772ecb 100644 > --- a/x86/lam.c > +++ b/x86/lam.c > @@ -231,13 +231,13 @@ static void test_lam_user(void) > bool has_lam = this_cpu_has(X86_FEATURE_LAM); > > /* > - * The physical address of AREA_NORMAL is within 36 bits, so that using > + * The physical address of AREA_LOW is within 36 bits, so that using > * identical mapping, the linear address will be considered as user mode > * address from the view of LAM, and the metadata bits are not used as > * address for both LAM48 and LAM57. > */ > - vaddr = alloc_pages_flags(0, AREA_NORMAL); > - static_assert((AREA_NORMAL_PFN & GENMASK(63, 47)) == 0UL); > + vaddr = alloc_pages_flags(0, AREA_LOW); > + static_assert((vaddr & GENMASK(63, 47)) == 0UL); > > /* > * Note, LAM doesn't have a global control bit to turn on/off LAM