linux-kernel - Re: [PATCH v3 5/6] x86/microcode/intel: Support mailbox transfer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z/+7O6pYQ8FkD+Xj@intel.com>
Date: Wed, 16 Apr 2025 22:14:19 +0800
From: Chao Gao <chao.gao@...el.com>
To: "Chang S. Bae" <chang.seok.bae@...el.com>
CC: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<colinmitchell@...gle.com>
Subject: Re: [PATCH v3 5/6] x86/microcode/intel: Support mailbox transfer

>+/*
>+ * Wait for the hardware to complete a transaction.
>+ * Return true on success, false on failure.
>+ */
>+static bool wait_for_transaction(struct staging_state *ss)
>+{
>+	u32 timeout, status;
>+
>+	/* Allow time for hardware to complete the operation: */
>+	for (timeout = 0; timeout < MBOX_XACTION_TIMEOUT_MS; timeout++) {
>+		msleep(1);
>+
>+		status = readl(ss->mmio_base + MBOX_STATUS_OFFSET);
>+		/* Break out early if the hardware is ready: */
>+		if (status & MASK_MBOX_STATUS_READY)
>+			break;

Shouldn't we exit the loop if the MASK_MBOX_STATUS_ERROR is set, or is the
ERROR bit always set in conjunction with the READY bit?

>+	}
>+
>+	status = readl(ss->mmio_base + MBOX_STATUS_OFFSET);

I still think this read is not needed.

>+
>+	/* Check for explicit error response */
>+	if (status & MASK_MBOX_STATUS_ERROR) {
>+		ss->state = UCODE_ERROR;
>+		return false;
>+	}
>+
>+	/*
>+	 * Hardware is neither responded to the action nor
>+	 * signaled any error. Treat the case as timeout.
>+	 */
>+	if (!(status & MASK_MBOX_STATUS_READY)) {
>+		ss->state = UCODE_TIMEOUT;
>+		return false;
>+	}
>+
>+	ss->state = UCODE_OK;
>+	return true;
>+}