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bh=g9H/C1PpC36IRqyjibUsIvzP3hGQMaqzwi6jG5cD2/k=; b=S8u0uFlo56x4SJF28DGuVASrEGaufHrfkZD42Js/oteIoLFAIadIi4lxOxGCdROXvRJ8x+nl4k8FHV4FbfAp8pAAavf43f1O+PXGMO80GMs9E4avFLObGREL5g14kukD116YjGP1yCSYLRRS4LnwkYEbx/hLPsVp/GKjWxOzfZU= X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB03.amd.com; pr=C From: Michal Orzel To: CC: Michal Orzel , Stefano Stabellini , Julien Grall , Bertrand Marquis , Volodymyr Babchuk Subject: [PATCH 1/3] xen/arm: vpl011: Fix misleading comments Date: Wed, 5 Apr 2023 13:17:48 +0200 Message-ID: <20230405111750.12491-2-michal.orzel@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230405111750.12491-1-michal.orzel@amd.com> References: <20230405111750.12491-1-michal.orzel@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6NAM11FT049:EE_|PH0PR12MB7094:EE_ X-MS-Office365-Filtering-Correlation-Id: 042fd97e-6201-403b-d9f8-08db35c7748c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Apr 2023 11:18:17.2427 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 042fd97e-6201-403b-d9f8-08db35c7748c X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT049.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7094 X-ZohoMail-DKIM: pass (identity @amd.com) X-ZM-MESSAGEID: 1680693536290100007 Content-Type: text/plain; charset="utf-8" In both vpl011_read_data() and vpl011_read_data_xen(), there is a comment stating that the guest is expected to read the DR register only if the TXFE bit of FR register is not set. This is obviously logically wrong and it should be RXFE (i.e. RX FIFO empty bit set -> nothing to read). Signed-off-by: Michal Orzel Reviewed-by: Ayan Kumar Halder Reviewed-by: Henry Wang Reviewed-by: Stefano Stabellini --- xen/arch/arm/vpl011.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c index 2fa80bc15ac4..0186d8a31834 100644 --- a/xen/arch/arm/vpl011.c +++ b/xen/arch/arm/vpl011.c @@ -143,8 +143,8 @@ static uint8_t vpl011_read_data_xen(struct domain *d) /* * It is expected that there will be data in the ring buffer when this * function is called since the guest is expected to read the data reg= ister - * only if the TXFE flag is not set. - * If the guest still does read when TXFE bit is set then 0 will be re= turned. + * only if the RXFE flag is not set. + * If the guest still does read when RXFE bit is set then 0 will be re= turned. */ if ( xencons_queued(in_prod, in_cons, sizeof(intf->in)) > 0 ) { @@ -202,8 +202,8 @@ static uint8_t vpl011_read_data(struct domain *d) /* * It is expected that there will be data in the ring buffer when this * function is called since the guest is expected to read the data reg= ister - * only if the TXFE flag is not set. - * If the guest still does read when TXFE bit is set then 0 will be re= turned. + * only if the RXFE flag is not set. + * If the guest still does read when RXFE bit is set then 0 will be re= turned. */ if ( xencons_queued(in_prod, in_cons, sizeof(intf->in)) > 0 ) { --=20 2.25.1 From nobody Wed May 15 12:23:40 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Apr 2023 11:18:18.6489 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 00ee4a16-6e8e-45a1-6a0d-08db35c77563 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT049.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB7669 X-ZohoMail-DKIM: pass (identity @amd.com) X-ZM-MESSAGEID: 1680693533162100001 Content-Type: text/plain; charset="utf-8" When backend is in Xen, the handling of data written to DR register is a bit special because we want to tell guest that we are always ready for new data to be written (i.e. no real FIFO, TXFF/BUSY never set and TXI always set). This conflicts with the current handling of TXFE bit, which we always clear and never set on a write path (we happen to set it when we receive char from serial input due to use of vpl011_data_avail() but this might never be called). This can lead to issues if a guest driver makes use of TXFE bit to check for TX transmission completion (such guest could then wait endlessly). Fix it by keeping TXFE always set to match the current emulation logic. Signed-off-by: Michal Orzel Reviewed-by: Henry Wang Reviewed-by: Stefano Stabellini Tested-by: Henry Wang --- We don't have to look far for an example of a PL011/SBSA driver relying on = TXFE. If a guest had a driver like we have in Xen, we would end up with no messag= es being printed. --- xen/arch/arm/vpl011.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c index 0186d8a31834..ff06deeb645c 100644 --- a/xen/arch/arm/vpl011.c +++ b/xen/arch/arm/vpl011.c @@ -112,8 +112,14 @@ static void vpl011_write_data_xen(struct domain *d, ui= nt8_t data) } } =20 + /* + * When backend is in Xen, we tell guest we are always ready for new d= ata + * to be written. This is fulfilled by having: + * - TXI/TXFE -> always set, + * - TXFF/BUSY -> never set. + */ vpl011->uartris |=3D TXI; - vpl011->uartfr &=3D ~TXFE; + vpl011->uartfr |=3D TXFE; vpl011_update_interrupt_status(d); =20 VPL011_UNLOCK(d, flags); --=20 2.25.1 From nobody Wed May 15 12:23:40 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; arc=pass (i=1 dmarc=pass fromdomain=amd.com); dmarc=pass(p=quarantine dis=none) header.from=amd.com ARC-Seal: i=2; a=rsa-sha256; t=1680693532; cv=pass; d=zohomail.com; s=zohoarc; b=JHaaacv5ada5GcRZXF7uiVyNDLgHaBrptELrKoBcfbI9T3GmO1MMJNbX/pFMJwoeYLHKSg8DzDtIRPpj/845LciPzAYMW0/CtL3PTEREaHSQkUYrDtSdrwvmZy/TrhfjkCExlzPxNQBVrj2GUxJ+RIZ9swlaXPePc4WKpKD4ZLw= ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1680693532; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; 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helo=lists.xenproject.org; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C From: Michal Orzel To: CC: Michal Orzel , Stefano Stabellini , Julien Grall , Bertrand Marquis , Volodymyr Babchuk Subject: [PATCH 3/3] xen/arm: vpl011: Do not try to handle TX FIFO status when backend in Xen Date: Wed, 5 Apr 2023 13:17:50 +0200 Message-ID: <20230405111750.12491-4-michal.orzel@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230405111750.12491-1-michal.orzel@amd.com> References: <20230405111750.12491-1-michal.orzel@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6NAM11FT061:EE_|IA1PR12MB7734:EE_ X-MS-Office365-Filtering-Correlation-Id: 3ddf0363-7b25-4ed1-c010-08db35c7765a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Apr 2023 11:18:20.2698 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3ddf0363-7b25-4ed1-c010-08db35c7765a X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT061.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7734 X-ZohoMail-DKIM: pass (identity @amd.com) X-ZM-MESSAGEID: 1680693535141100005 Content-Type: text/plain; charset="utf-8" From vpl011_rx_char_xen(), we call vpl011_data_avail() that handles both RX and TX state. Because we are passing 0 as out_fifo_level and SBSA_UART_FIFO_SIZE as out_size, we end up calling a function vpl011_update_tx_fifo_status() which performs TXI bit handling depending on the FIFO trigger level. This does not make sense when backend is in Xen, as we maintain a single TX state where data can always be written and as such there is no TX FIFO handling. Furthermore, this function assumes that the backend is in domain by making use of struct xencons_interface unconditionally. Fix it by calling this function only when backend is in domain. Also add an assert for sanity. Signed-off-by: Michal Orzel Reviewed-by: Stefano Stabellini Tested-by: Henry Wang --- xen/arch/arm/vpl011.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c index ff06deeb645c..7856b4b5f5a3 100644 --- a/xen/arch/arm/vpl011.c +++ b/xen/arch/arm/vpl011.c @@ -261,6 +261,9 @@ static void vpl011_update_tx_fifo_status(struct vpl011 = *vpl011, struct xencons_interface *intf =3D vpl011->backend.dom.ring_buf; unsigned int fifo_threshold =3D sizeof(intf->out) - SBSA_UART_FIFO_LEV= EL; =20 + /* No TX FIFO handling when backend is in Xen */ + ASSERT(vpl011->backend_in_domain); + BUILD_BUG_ON(sizeof(intf->out) < SBSA_UART_FIFO_SIZE); =20 /* @@ -547,7 +550,13 @@ static void vpl011_data_avail(struct domain *d, */ vpl011->uartfr &=3D ~BUSY; =20 - vpl011_update_tx_fifo_status(vpl011, out_fifo_level); + /* + * When backend is in Xen, we are always ready for new data to be + * written (i.e. no TX FIFO handling), therefore we do not want + * to change the TX FIFO status in such case. + */ + if ( vpl011->backend_in_domain ) + vpl011_update_tx_fifo_status(vpl011, out_fifo_level); } =20 vpl011_update_interrupt_status(d); --=20 2.25.1