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 33EB027A10A for ; Tue, 15 Apr 2025 22:15:22 +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=1744755324; cv=none; b=CT982iu+6al+rnRLcOkwtH6ly50X5FsNOsSPTnK/jzlWa+K2DyAZ6BQP2sAhpoi9y5J3whcn0WaVGWQ6jMkkmU9lNzt5GPfrxZgKpEwhmVLgSEwjAQxqVs+31Li67ILnPEtIJFrFpP/whNBQ/Ta+rhJnphBdYpdyZXd1XlPF9X0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744755324; c=relaxed/simple; bh=wiubO1rowJJ7Bd/abC83QrnLeIgusBUrsszAL9POhpQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=MJdh9PLQcfNaL/W2L/u2Ndcy6Ss5DonPS4NGEiPf8525r1wvW1tHubxwTI1ey0Jf1AB1qMQy3C1VaH9uxr8ChK9F2ZN6jzdDCjW0gVN9J72lR/oNAQ7wGHZF/dLFnVFVplhUumEBbmwh5M0iOmDT4rT/mm0XbelDnqqhvAQa+R0= 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=Km+XnxWT; 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="Km+XnxWT" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-2ff53a4754aso8233645a91.2 for ; Tue, 15 Apr 2025 15:15:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1744755322; x=1745360122; 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=Ry9xEwNaBzqQYPUr2sJCAn+hzw6WkQUhzGrae9Rjk7I=; b=Km+XnxWTWEXmcoi4EJAFrph0ly+biRnMcNohDNRhRN4kpbbeVKVfQR1qm5U88N3GZ8 cG92m7nceKFaTkQvsDkgY5Dimo4bTzdJqcI2itzLvb67MSw2epzv5cNrR6bwZMO5k+6L FAZsSoxrcBWo/9GR2M14pEfOIb2Wndp2y0BybN8rH58K4yOMPJbRJ2IYEPTvzBydfKtd 1wt7J/TUO+WpF00wrO7gSihZX8F7TUdZwQNzme7uC8rm2dvLOurV6H+m1wT1Chr6p98d eIVPDjE3SK8pqgC/dSx6NbcPhUr6BFzOT1XlB/TgjrRcrj98jtM9j7e7UMwDJxtgvRjF 7dkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744755322; x=1745360122; 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=Ry9xEwNaBzqQYPUr2sJCAn+hzw6WkQUhzGrae9Rjk7I=; b=BdE6uZNPuPoh7Lgj/UBtORu0XRU5wV/9CPCr6jw591dKK7KGyZwtU94WJR8LKXBznd T+VEvUGNbaNVzQjynNESqc+yuCpbo3ahVH2NIE7cvsP459c8y8qXCDBRyqWdIQsYsOLc VDfhbyuQFUlrCfDhHpworJmtuT5Ar7pGlHAVWLNqeOjQjIpQCycmONfN5Z466s8HejPm PAgS/8O05K9CXTH2VEq7OJg252JQ1ZSo1BJqOLeSlOoU17bM6LxsHUEPW1/K9sx8eqcd ZltjefZUMKZ4WMmQi1XiZrdVHxmZGUcDYSJSzcInR85I9gW1eMM8lCZRjfYZzTs/eR1U 8qPQ== X-Forwarded-Encrypted: i=1; AJvYcCXAl958z+QNO6VvJ+81P0g3zeturjXA9KHEZ6MKhyV0Rd82uzfI3kQLy0G9tV6AoXZhlxn5+o23mS55TJs=@vger.kernel.org X-Gm-Message-State: AOJu0YwvDp8cXT+wmG4jAwDPvhnCYhl/Y/T1C8F5yK/XPd/VegJ7OWTo 4+0neQ/7yz5qAG2Pa3KPbGTqixuhqCnovWTHdeNR81QBXQSiCcWNVx19YsiYm1xjcqCRWCMDMbU r4w== X-Google-Smtp-Source: AGHT+IG9a+i7AqRB2/IlyNo5DtSnN1pt7IPfUfiPrFvNunVgOzcitRLYND0tYsvNeLieAMV60IKunKQjhZg= X-Received: from pjci30.prod.google.com ([2002:a17:90a:3da1:b0:2fa:2891:e310]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:5484:b0:2fa:137f:5c61 with SMTP id 98e67ed59e1d1-3085eeb5078mr1496593a91.12.1744755322545; Tue, 15 Apr 2025 15:15:22 -0700 (PDT) Date: Tue, 15 Apr 2025 15:15:21 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250410204149.2576104-1-ross.philipson@oracle.com> <20250410204149.2576104-10-ross.philipson@oracle.com> Message-ID: Subject: Re: [PATCH v13 09/19] x86: Secure Launch kernel early boot stub From: Sean Christopherson To: Andrew Cooper Cc: Ross Philipson , linux-kernel@vger.kernel.org, x86@kernel.org, linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org, linux-crypto@vger.kernel.org, kexec@lists.infradead.org, linux-efi@vger.kernel.org, iommu@lists.linux.dev, dpsmith@apertussolutions.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com, ardb@kernel.org, mjg59@srcf.ucam.org, James.Bottomley@hansenpartnership.com, peterhuewe@gmx.de, jarkko@kernel.org, jgg@ziepe.ca, luto@amacapital.net, nivedita@alum.mit.edu, herbert@gondor.apana.org.au, davem@davemloft.net, corbet@lwn.net, ebiederm@xmission.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, kanth.ghatraju@oracle.com, trenchboot-devel@googlegroups.com Content-Type: text/plain; charset="us-ascii" On Tue, Apr 15, 2025, Andrew Cooper wrote: > On 11/04/2025 10:40 pm, Sean Christopherson wrote: > > On Thu, Apr 10, 2025, Ross Philipson wrote: > >> + * instruction can return for a number of reasons. Test to see if it returned > >> + * because the monitor was written to. > >> + */ > >> + monitor > >> + > >> +1: > >> + mfence > >> + mwait > >> + movl (%eax), %edx > > Why load the value into EDX? At a glance, the value is never consumed. > > > >> + testl %edx, %edx > >> + jz 1b > > This usage of MONITOR/MWAIT is flawed. The monitor needs to be re-armed in each > > loop, otherwise mwait will be a glorified nop. > > > > More importantly, the exit condition needs to be checked before monitor, > > after monitor and before mwait. Gah, yeah, I mean to say "before mwait".