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To: Peter Bergner , libc-alpha@sourceware.org Cc: rajis@linux.ibm.com, Mahesh Bodapati References: <20230619080956.3187040-1-bmahi496@linux.ibm.com> <94be5917-3607-6e45-115f-a2f6db95b321@linux.ibm.com> From: MAHESH BODAPATI In-Reply-To: <94be5917-3607-6e45-115f-a2f6db95b321@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: sue2XwWT98H0k6RXj2JfmuahDGcxAYbm X-Proofpoint-ORIG-GUID: sue2XwWT98H0k6RXj2JfmuahDGcxAYbm X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-06-20_13,2023-06-16_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 adultscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxlogscore=798 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000 definitions=main-2306200159 X-Spam-Status: No, score=-4.7 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 20/06/23 9:50 pm, Peter Bergner wrote: > On 6/19/23 3:09 AM, bmahi496--- via Libc-alpha wrote: >> This patch enables the option to influence hwcaps used by the powerpc. >> The user can set a CPU arch-level tunable like power10 instead of single >> HWCAP features. >> >> The influenced hwcap are stored in the powerpc-specific cpu_features struct. >> >> Below are the supported cpu arch-level tunables. >> - power10: power10 feature set >> - power9: power9 feature set >> - power8: power8 feature set >> - power7: power7 feature set >> - power6: power6 feature set >> - power5: power5 feature set >> - power4: power4 feature set. > I'm all for allowing modifying full cpu specific hwcap tunables with one > "cpu" option, but it's hard to tell whether this change allows modifying > single HWCAP/HWCAP2 features too. Say I only want to disable the VSX > feature or the MMA feature and nothing else. Does this patch support that? > We *do* want that ability! > This patch will not support single HWCAP/HWCAP2 features. This is only for CPU arch-level features. We can add tunable support for single HWCAP/HWCAP2 in a separate patch. > > >> + /* we don't disable altivec and vsx */ > This is not a correctly formatted sentence with proper capitalization, etc. > I will update the sentence. > >> + if (disable_vsx) >> + cpu_features_curr.hwcap &= ~PPC_FEATURE_HAS_VSX; > Why the special handling for the VSX feature here? How is it different > than say the Altivec feature or any of our other feature bits which don't > have special handling? It's not obvious to me why we need special handling, > so it's probably not obvious to others either. If we really do need special > handling for this, you should add a comment explaining why. > On PowerPC32, The function selection happened through VSX feature on some libraries. Say I set tunable as "power7,power6" then it should set to power6 but it's picking the power7 specific code So I am disabling VSX feature on the machines which are lower than power7 and the code should work on the precedence as well, For suppose "power6,power7" then it should set to power7. >> + /* Copy back the supported tunable features */ > Missing a '.' and 2 spaces before the */ > I will update the sentence. > Peter > >