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X-MS-Exchange-AntiSpam-MessageData: =?gb2312?B?TEhNMFhPbW9mTVJ4NHF6QVFsQ3FSWXpjTlpPM2dTOGJnT2dLVW5xZFlhNEVr?= =?gb2312?B?MUpJM1VSQ3FIZm9MaUZwUHNMOThIaExZUUZhem0rdDlOUzZsNEVvVmxLK3U5?= =?gb2312?B?YkpNekJxdFh2Zm84Q2RGMm5XVWt3QmsrZWliWjJiQXp4MWJCaWJIVWpTWXky?= =?gb2312?B?elpkRUo0cElhZHo5ZmJ1bWJJcjdlWXE0T0F4eUxkQm9kb3Y5MXA1T2VZSnZB?= =?gb2312?B?MGtMWldhZm8xSnZOdUx4ZnU5bWtEdnFXNGl3RzVmV3V5eHFqSjAxQ2ZwclRp?= =?gb2312?B?WmRtK1Bjdkl1UWg3UFhDcE1BekZndHdrbzB4MlRyY0RJU3k0SjlIWmhoY2VS?= =?gb2312?B?TTBJZ0lEY3psWFdJUWhpdklxWjZYS1pTdm93a0J6OGc2Q0J5aXp0ano4S3Zh?= =?gb2312?B?ZmpwRW1FcjR3aUVnUTJSNlFvWDgzenh1a01aL01uTFplaTN0WTV1QzVsdXBa?= =?gb2312?B?RTNGVFVjT1c5ajZhVzhmOTBCU2hINnI0cEcxclVlR05seSs2ckJ5eklHS0pk?= =?gb2312?B?TjU1QWVDT2ljUHJrSG9ib2VVU1JFeVdpWVA4Z3ViblZaMnpVMXFUemdPQUN2?= =?gb2312?B?dHUxWGRrS1YvS1NGSTBCZXB6WER0ZzRLWnlLZ3VQWDh6M3lWVnlSNW1UZ253?= =?gb2312?B?N0xXdUFkY21WdFprWmlsZnU0OUVzNSsvRW5TM1FBZlFYZFVBR0dVQUJLN2do?= =?gb2312?B?S0dlOHpJUytVOTF1RXhSWmh4a3IrbUR2VXhjQjhBU1hJejVkQ0hNREp0VWll?= =?gb2312?B?MFhCTXBzL2VyVmprd1plbHJDY0svd0tYcDJGbWNrdWgrQWxRWnFNalRKZEFm?= =?gb2312?B?aStuMGlDOFdBU0N0TWlaeVJLd1dCdERmSEh2a3hCR2Uzb2JGVGdpV2JLZjBu?= =?gb2312?B?eXd3QTZkVzU0VXg0V2RIRVFzTlVvMEJqOVNBWnIySE9WYXhJTWRCcWpoMzk4?= =?gb2312?B?c2I3S1c4T3JDUE5qL1JTVFNmQjNLVVkwVkpFZERoRlJyWU4xSmNobVJ1aEdk?= =?gb2312?B?dlp2V2N3V2N1WnAxb0ErbmZEVlFVaXdTQkh1WHJlQlJaWjNjdFNMc1I5a1NQ?= =?gb2312?B?TXNqM1V1LzlOUmFMeUNMQnJOcysyVzV5ZHJWZVBkSjFQUUZOMkVrMkNSWkk4?= =?gb2312?B?UG9DQ2w0ZmVhYk1lcC9hVDJkQU96c0ljYURKSDZjc2UxQmlYYUxqWEFuMWtM?= =?gb2312?B?WjA2M3QvaUlTcGxNNElBTUVBZW94UzhvQWM1bXpTMmZpMElMWEZHZEFkNUx2?= =?gb2312?B?RWE3ejVocDFMWlZtVVhOR1p3M0xQN0VlYnI3Z0gxc09Nb3J1WG50SWpzV0Mz?= =?gb2312?B?UnN2c2kzMXcybjVjbDFPN2hCMWNHeVh2U2dvWEFXazhVOGpEK1d2dDA1NGtQ?= =?gb2312?B?U3JueEhNNllabEt0Ym5CWFl1U1hTdzdzMng1YnZtQTR0SEtndXJyWjBvR0NN?= =?gb2312?B?UEhwOENRc2Q3WUJVOUU4VGgyWlVwUldtVnJFM2FWQzE1TjlERzBNMHRscmxC?= =?gb2312?B?YzFoL2hLcy9LUG9OR3VSNFZlWVRya0twU1k0WUIvT1JZSUU2cCs3cGpULzJI?= =?gb2312?B?VmhsbTRwMytvVE1TcjhSc3NoRmc5ZUNlQTFmb2o4Ujd2aC96WktHOENhTTUz?= =?gb2312?B?NUcyODc1eTJFQmlaOG1qaVhhUWllWDNuTWVMSE1ERkkzNHRiQldyL3ptbTc5?= =?gb2312?B?Nnh1OHZ1SXRqbTZNVURNajZkMlIzQTIzTjdUU2dOUXA4MHByNm9HRkRveFBR?= =?gb2312?Q?HK+Z7GDnvpi5e2C27yaGrbPLngVcm5e7q1eA5Ko?= X-OriginatorOrg: cipunited.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6d9195f1-dbb8-4408-bb04-08d8dde80f34 X-MS-Exchange-CrossTenant-AuthSource: HKAPR04MB3956.apcprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Mar 2021 02:00:03.3784 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: e31cf5b5-ee69-4d5f-9c69-edeeda2458c0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: +JM7YHQAKAIde17iUcgyLEbQKFzAs9xoEeW3Xxq15VLQkCa5rVIDpUebsqTd09y9TnwJrIKBzauLHwy9NllcfwRKRINGklOAXs9+fSm1KOw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: HK0PR04MB2915 Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org > On Tue, 2 Mar 2021, YunQiang Su wrote: > > > The MIPS FPU may have 2 mode: > > FR=0: MIPS I style, odd-FPR can only be single, > > and even-FPR can be double. > > Depending on the ISA level FR=0 may or may not allow single arithmetic with > odd-numbered FPRs. Compare the FP64A ABI. > > > FR=1: all 32 FPR can be double. > > I think it's best to describe the FR=0 mode as one where the FP registers are > 32-bit and the FR=1 mode as one where the FP registers are 64-bit (this mode > is also needed for the paired-single format). See: > > king#1._Introduction> > Thank you. I will update it. > > The binary may have 3 mode: > > FP32: can only work with FR=0 mode > > FPXX: can work with both FR=0 and FR=1 mode. > > FP64: can only work with FR=1 mode > > > > Some binary, for example the output of golang, may be mark as FPXX, > > while in fact they are FP32. > > > > Currently, FR=1 mode is used for all FPXX binary, it makes some wrong > > behivour of the binaries. Since FPXX binary can work with both FR=1 > > and FR=0, we force it to use FR=0. > > I think you need to document here what we discussed, that is the linker bug > exposed in the context of FPXX annotation by legacy modules that lack FP > mode annotation, which is the underlying problem. I will do it. > > > v5->v6: > > Rollback to V3, aka remove config option. > > You can't reuse v3 as it stands because it breaks R6 as we previously > discussed. You need to tell R6 and earlier ISAs apart and set the FR bit > accordingly. > It won't break r6, as all of r6 binary is FP64, and on r6 `frdefault' is always false, and `fr1' is always true. It won't trigger this mode switch. Oh, you are right, there may be a case that to run legacy app on r6 CPU. For this case, on r6, we need to set the CPU to FRE mode. > It would be more proper I suppose if we actually checked at the boot time > whether the bit is writable, just like we handle NAN2008, but I don't see it as > a prerequisite for this workaround since we currently don't do this either (it > would also be good to check if the FP emulation code gets the read-only FR bit > right for R6 for FPU-less operation). > Check writable is not needed here. > Also you need to put the history in the comment section and not the commit > description, so that the change can be directly applied and does not have to > be hand-edited by the maintainer. You don't want to overload him with > mechanical work. > Ok, I will add more comment. > Maciej