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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: Content-Language: en-US To: Jiamei Xie , CC: Stefano Stabellini , Julien Grall , Bertrand Marquis , "Volodymyr Babchuk" , Wei Chen References: <20221118020013.125987-1-jiamei.xie@arm.com> From: Michal Orzel In-Reply-To: <20221118020013.125987-1-jiamei.xie@arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6NAM11FT040:EE_|CY5PR12MB6407:EE_ X-MS-Office365-Filtering-Correlation-Id: af107f6e-cfc6-4828-8d7a-08dac939245f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230022)(4636009)(376002)(346002)(136003)(39860400002)(396003)(451199015)(36840700001)(40470700004)(46966006)(31686004)(40460700003)(36756003)(82310400005)(31696002)(86362001)(3480700007)(81166007)(82740400003)(40480700001)(336012)(36860700001)(356005)(53546011)(47076005)(426003)(83380400001)(186003)(2616005)(26005)(316002)(8676002)(110136005)(478600001)(2906002)(41300700001)(7116003)(16576012)(54906003)(5660300002)(70586007)(966005)(4326008)(44832011)(8936002)(70206006)(43740500002)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Nov 2022 07:47:28.6126 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: af107f6e-cfc6-4828-8d7a-08dac939245f 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: DM6NAM11FT040.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6407 Hi Jimaei, On 18/11/2022 03:00, Jiamei Xie wrote: > > > Date: Thu, 17 Nov 2022 11:07:12 +0800 > Subject: [PATCH] xen/arm: vpl011: Make access to DMACR write-ignore > > When the guest kernel enables DMA engine with "CONFIG_DMA_ENGINE=y", > Linux SBSA PL011 driver will access PL011 DMACR register in some > functions. As chapter "B Generic UART" in "ARM Server Base System > Architecture"[1] documentation describes, SBSA UART doesn't support > DMA. In current code, when the kernel tries to access DMACR register, > Xen will inject a data abort: > Unhandled fault at 0xffffffc00944d048 > Mem abort info: > ESR = 0x96000000 > EC = 0x25: DABT (current EL), IL = 32 bits > SET = 0, FnV = 0 > EA = 0, S1PTW = 0 > FSC = 0x00: ttbr address size fault > Data abort info: > ISV = 0, ISS = 0x00000000 > CM = 0, WnR = 0 > swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000020e2e000 > [ffffffc00944d048] pgd=100000003ffff803, p4d=100000003ffff803, pud=100000003ffff803, pmd=100000003fffa803, pte=006800009c090f13 > Internal error: ttbr address size fault: 96000000 [#1] PREEMPT SMP > ... > Call trace: > pl011_stop_rx+0x70/0x80 > tty_port_shutdown+0x7c/0xb4 > tty_port_close+0x60/0xcc > uart_close+0x34/0x8c > tty_release+0x144/0x4c0 > __fput+0x78/0x220 > ____fput+0x1c/0x30 > task_work_run+0x88/0xc0 > do_notify_resume+0x8d0/0x123c > el0_svc+0xa8/0xc0 > el0t_64_sync_handler+0xa4/0x130 > el0t_64_sync+0x1a0/0x1a4 > Code: b9000083 b901f001 794038a0 8b000042 (b9000041) > ---[ end trace 83dd93df15c3216f ]--- > note: bootlogd[132] exited with preempt_count 1 > /etc/rcS.d/S07bootlogd: line 47: 132 Segmentation fault start-stop-daemon > > As discussed in [2], this commit makes the access to DMACR register > write-ignore as an improvement. As discussed earlier, if we decide to improve vpl011 (for now only Stefano shared his opinion), then we need to mark *all* the PL011 registers that are not part of SBSA ar RAZ/WI. So handling DMACR and only for writes is not beneficial (it is only fixing current Linux issue, but what we really want is to improve the code in general). > > [1] https://developer.arm.com/documentation/den0094/c/?lang=en > [2] https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2211161552420.4020@ubuntu-linux-20-04-desktop/ > > Signed-off-by: Jiamei Xie > --- > xen/arch/arm/vpl011.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c > index 43522d48fd..80d00b3052 100644 > --- a/xen/arch/arm/vpl011.c > +++ b/xen/arch/arm/vpl011.c > @@ -463,6 +463,7 @@ static int vpl011_mmio_write(struct vcpu *v, > case FR: > case RIS: > case MIS: > + case DMACR: > goto write_ignore; > > case IMSC: > -- > 2.25.1 > > ~Michal