From nobody Sun Apr 28 22:28:53 2024 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9077FC76196 for ; Tue, 28 Mar 2023 15:19:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233205AbjC1PTK (ORCPT ); Tue, 28 Mar 2023 11:19:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232837AbjC1PS3 (ORCPT ); Tue, 28 Mar 2023 11:18:29 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 69099BDC6; Tue, 28 Mar 2023 08:17:20 -0700 (PDT) Received: from vm02.corp.microsoft.com (unknown [167.220.197.27]) by linux.microsoft.com (Postfix) with ESMTPSA id 89F4E20FD945; Tue, 28 Mar 2023 08:16:40 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 89F4E20FD945 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1680016601; bh=4wfUXWdj4oVNf4M9M6kxy7m6WtmwRmZ9/vKCpDdemjg=; h=From:To:Cc:Subject:Date:From; b=ahUYFXqX7hTR7FwJDnDyJURJgQZD0AcoFgTvWMEVjeUG5CG6dUXovRdOHYJ9iPDuX OL3cTN1jUmd9QGFfV19Ll8l9qdIBd4C6I2looSA1m+eFUmGb1lzEpHDK78YY+9eeDr TL7je9PVE2pTsjEO9OMHWmv6RV0Mmh9Td88Ooes0= From: Jeremi Piotrowski To: linux-crypto@vger.kernel.org Cc: Jeremi Piotrowski , Tom Lendacky , John Allen , Herbert Xu , Brijesh Singh , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] crypto: ccp - Clear PSP interrupt status register before calling handler Date: Tue, 28 Mar 2023 15:16:36 +0000 Message-Id: <20230328151636.1353846-1-jpiotrowski@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The PSP IRQ is edge-triggered (MSI or MSI-X) in all cases supported by the psp module so clear the interrupt status register early in the handler to prevent missed interrupts. sev_irq_handler() calls wake_up() on a wait queue, which can result in a new command being submitted from a different CPU. This then races with the clearing of isr and can result in missed interrupts. A missed interrupt results in a command waiting until it times out, which results in the psp being declared dead. This is unlikely on bare metal, but has been observed when running virtualized. In the cases where this is observed, sev->cmdresp_reg has PSP_CMDRESP_RESP set which indicates that the command was processed correctly but no interrupt was asserted. The full sequence of events looks like this: CPU 1: submits SEV cmd #1 CPU 1: calls wait_event_timeout() CPU 0: enters psp_irq_handler() CPU 0: calls sev_handler()->wake_up() CPU 1: wakes up; finishes processing cmd #1 CPU 1: submits SEV cmd #2 CPU 1: calls wait_event_timeout() PSP: finishes processing cmd #2; interrupt status is still set; no interr= upt CPU 0: clears intsts CPU 0: exits psp_irq_handler() CPU 1: wait_event_timeout() times out; psp_dead=3Dtrue Fixes: 200664d5237f ("crypto: ccp: Add Secure Encrypted Virtualization (SEV= ) command support") Cc: stable@vger.kernel.org Signed-off-by: Jeremi Piotrowski Acked-by: Tom Lendacky --- drivers/crypto/ccp/psp-dev.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c index c9c741ac8442..949a3fa0b94a 100644 --- a/drivers/crypto/ccp/psp-dev.c +++ b/drivers/crypto/ccp/psp-dev.c @@ -42,6 +42,9 @@ static irqreturn_t psp_irq_handler(int irq, void *data) /* Read the interrupt status: */ status =3D ioread32(psp->io_regs + psp->vdata->intsts_reg); =20 + /* Clear the interrupt status by writing the same value we read. */ + iowrite32(status, psp->io_regs + psp->vdata->intsts_reg); + /* invoke subdevice interrupt handlers */ if (status) { if (psp->sev_irq_handler) @@ -51,9 +54,6 @@ static irqreturn_t psp_irq_handler(int irq, void *data) psp->tee_irq_handler(irq, psp->tee_irq_data, status); } =20 - /* Clear the interrupt status by writing the same value we read. */ - iowrite32(status, psp->io_regs + psp->vdata->intsts_reg); - return IRQ_HANDLED; } =20 --=20 2.34.1