From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: From: "Derrick, Jonathan" To: "helgaas@kernel.org" CC: "linux-kernel@vger.kernel.org" , "okaya@kernel.org" , "willy@infradead.org" , "liudongdong3@huawei.com" , "poza@codeaurora.org" , "linux-pci@vger.kernel.org" , "Busch, Keith" , "linux-doc@vger.kernel.org" Subject: Re: [PATCH 1/2] PCI/DPC: Add 'nodpc' parameter Date: Thu, 16 Aug 2018 20:50:42 +0000 Message-ID: <1534452635.17819.53.camel@intel.com> References: <1534368400-2807-1-git-send-email-jonathan.derrick@intel.com> <20180816154940.GD5762@bombadil.infradead.org> <1534434641.17819.27.camel@intel.com> <20180816203111.GB10316@bhelgaas-glaptop.roam.corp.google.com> In-Reply-To: <20180816203111.GB10316@bhelgaas-glaptop.roam.corp.google.com> Content-Type: multipart/signed; micalg=sha-1; protocol="application/x-pkcs7-signature"; boundary="=-Ak3dLlDYEWWixhmHkk0H" MIME-Version: 1.0 List-ID: --=-Ak3dLlDYEWWixhmHkk0H Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Bjorn, On Thu, 2018-08-16 at 15:31 -0500, Bjorn Helgaas wrote: > On Thu, Aug 16, 2018 at 03:50:47PM +0000, Derrick, Jonathan wrote: > > On Thu, 2018-08-16 at 08:49 -0700, Matthew Wilcox wrote: > > > On Wed, Aug 15, 2018 at 03:26:39PM -0600, Jon Derrick wrote: > > > > Some users may want to disable downstream port containment > > > > (DPC), > > > > so > > > > give them this option > > >=20 > > > Is it possible they might only want to disable DPC on a subset of > > > the > > > hierarchy rather than globally? > >=20 > > Absolutely. I was hoping Logan's pci dev_str would land because I > > have > > a few others I want to convert to that api for granular tuning >=20 > What's the use case here? I acknowledge there are cases where we > need > them, but I'm not a fan of kernel parameters in general because > they're a real hassle for users. >=20 > Is there something wrong with DPC? Is there some way we can make it > smarter so it does the right thing automatically? I've encountered some BIOS or switches (not sure who) who've appeared to have enabled DPC by default, prior to kernel setup. Some users may just not want this, but it was primarily intended for debugging when I conceived it. There's also the ongoing thread in linux-pci about err handling in PPC EEH, who may also desire to disable DPC until those issues are resolved. It can also be disabled with setpci, but is that any less of a hassle? Genuine question to understand your point of view. >=20 > I'm more OK with a blanket "nodpc" switch intended for debugging. > If we add the complexity of subsets of the hierarchy it starts > sounding like an administrative thing that makes me more hesitant.=20 >=20 That's ok with me. I was having trouble cleanly keeping the string around after early_param anyways. To again understand your point of view, is there anything wrong with administrative things in kernel boot parameters? There will be cases where we may want to deviate from default or global pci=3D* parameters for certain hierarchies and they can't necessarily be set after the fact (ex, hpmemsize). > Could this be done via a sysfs switch instead? That potentially > could > work for hot-added things where a kernel parameter doesn't work so > well. >=20 > Please squash the doc patch and the code change so it's easier to > keep > them together. >=20 > Bjorn --=-Ak3dLlDYEWWixhmHkk0H Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIKeTCCBOsw ggPToAMCAQICEFLpAsoR6ESdlGU4L6MaMLswDQYJKoZIhvcNAQEFBQAwbzELMAkGA1UEBhMCU0Ux FDASBgNVBAoTC0FkZFRydXN0IEFCMSYwJAYDVQQLEx1BZGRUcnVzdCBFeHRlcm5hbCBUVFAgTmV0 d29yazEiMCAGA1UEAxMZQWRkVHJ1c3QgRXh0ZXJuYWwgQ0EgUm9vdDAeFw0xMzAzMTkwMDAwMDBa Fw0yMDA1MzAxMDQ4MzhaMHkxCzAJBgNVBAYTAlVTMQswCQYDVQQIEwJDQTEUMBIGA1UEBxMLU2Fu dGEgQ2xhcmExGjAYBgNVBAoTEUludGVsIENvcnBvcmF0aW9uMSswKQYDVQQDEyJJbnRlbCBFeHRl cm5hbCBCYXNpYyBJc3N1aW5nIENBIDRBMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA 4LDMgJ3YSVX6A9sE+jjH3b+F3Xa86z3LLKu/6WvjIdvUbxnoz2qnvl9UKQI3sE1zURQxrfgvtP0b Pgt1uDwAfLc6H5eqnyi+7FrPsTGCR4gwDmq1WkTQgNDNXUgb71e9/6sfq+WfCDpi8ScaglyLCRp7 ph/V60cbitBvnZFelKCDBh332S6KG3bAdnNGB/vk86bwDlY6omDs6/RsfNwzQVwo/M3oPrux6y6z yIoRulfkVENbM0/9RrzQOlyK4W5Vk4EEsfW2jlCV4W83QKqRccAKIUxw2q/HoHVPbbETrrLmE6RR Z/+eWlkGWl+mtx42HOgOmX0BRdTRo9vH7yeBowIDAQABo4IBdzCCAXMwHwYDVR0jBBgwFoAUrb2Y ejS0Jvf6xCZU7wO94CTLVBowHQYDVR0OBBYEFB5pKrTcKP5HGE4hCz+8rBEv8Jj1MA4GA1UdDwEB /wQEAwIBhjASBgNVHRMBAf8ECDAGAQH/AgEAMDYGA1UdJQQvMC0GCCsGAQUFBwMEBgorBgEEAYI3 CgMEBgorBgEEAYI3CgMMBgkrBgEEAYI3FQUwFwYDVR0gBBAwDjAMBgoqhkiG+E0BBQFpMEkGA1Ud HwRCMEAwPqA8oDqGOGh0dHA6Ly9jcmwudHJ1c3QtcHJvdmlkZXIuY29tL0FkZFRydXN0RXh0ZXJu YWxDQVJvb3QuY3JsMDoGCCsGAQUFBwEBBC4wLDAqBggrBgEFBQcwAYYeaHR0cDovL29jc3AudHJ1 c3QtcHJvdmlkZXIuY29tMDUGA1UdHgQuMCygKjALgQlpbnRlbC5jb20wG6AZBgorBgEEAYI3FAID oAsMCWludGVsLmNvbTANBgkqhkiG9w0BAQUFAAOCAQEAKcLNo/2So1Jnoi8G7W5Q6FSPq1fmyKW3 sSDf1amvyHkjEgd25n7MKRHGEmRxxoziPKpcmbfXYU+J0g560nCo5gPF78Wd7ZmzcmCcm1UFFfIx fw6QA19bRpTC8bMMaSSEl8y39Pgwa+HENmoPZsM63DdZ6ziDnPqcSbcfYs8qd/m5d22rpXq5IGVU tX6LX7R/hSSw/3sfATnBLgiJtilVyY7OGGmYKCAS2I04itvSS1WtecXTt9OZDyNbl7LtObBrgMLh ZkpJW+pOR9f3h5VG2S5uKkA7Th9NC9EoScdwQCAIw+UWKbSQ0Isj2UFL7fHKvmqWKVTL98sRzvI3 seNC4DCCBYYwggRuoAMCAQICEzMAAKye+0C3syvSXOcAAAAArJ4wDQYJKoZIhvcNAQEFBQAweTEL MAkGA1UEBhMCVVMxCzAJBgNVBAgTAkNBMRQwEgYDVQQHEwtTYW50YSBDbGFyYTEaMBgGA1UEChMR SW50ZWwgQ29ycG9yYXRpb24xKzApBgNVBAMTIkludGVsIEV4dGVybmFsIEJhc2ljIElzc3Vpbmcg Q0EgNEEwHhcNMTcxMDE5MTcyNzI3WhcNMTgxMDE0MTcyNzI3WjBHMRowGAYDVQQDExFEZXJyaWNr LCBKb25hdGhhbjEpMCcGCSqGSIb3DQEJARYaam9uYXRoYW4uZGVycmlja0BpbnRlbC5jb20wggEi MA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCz4TvOwEKxVEgGst/n3LricX9KG2YbHHvorBFb ggk/Wm7ZV9v/w5I5+M7SFD1CVS+MD24tlcL0mjddPXklsjPNmFb7TCXhppQMWqxwlS44iokDpHEF wx6DtwcIlfmvgPormri3U5V0gkRvnmiFSlQ2bUycWgxttAvR4sYjxLas7hE3jZJ1LJ9IxiD7VMNJ QWXSxxnOGZVf1tUTqC5uNv9wSvr8N7ZRYldP4nJ9JUFO7bazyoplxGlgxIR3+7I9TgbrUOziQCja AG6qjTBc2iB2iz6IVnzrBtQT5DR3KM6EqbMTwur8keTC11xls7lwWexzsSgt37V9UNKAqfsZPgcX AgMBAAGjggI3MIICMzAdBgNVHQ4EFgQUJRdznv8EeAa3g+3F5NKtNNctuBcwHwYDVR0jBBgwFoAU HmkqtNwo/kcYTiELP7ysES/wmPUwZQYDVR0fBF4wXDBaoFigVoZUaHR0cDovL3d3dy5pbnRlbC5j b20vcmVwb3NpdG9yeS9DUkwvSW50ZWwlMjBFeHRlcm5hbCUyMEJhc2ljJTIwSXNzdWluZyUyMENB JTIwNEEuY3JsMIGfBggrBgEFBQcBAQSBkjCBjzBpBggrBgEFBQcwAoZdaHR0cDovL3d3dy5pbnRl bC5jb20vcmVwb3NpdG9yeS9jZXJ0aWZpY2F0ZXMvSW50ZWwlMjBFeHRlcm5hbCUyMEJhc2ljJTIw SXNzdWluZyUyMENBJTIwNEEuY3J0MCIGCCsGAQUFBzABhhZodHRwOi8vb2NzcC5pbnRlbC5jb20v MAsGA1UdDwQEAwIHgDA8BgkrBgEEAYI3FQcELzAtBiUrBgEEAYI3FQiGw4x1hJnlUYP9gSiFjp9T gpHACWeB3r05lfBDAgFkAgEJMB8GA1UdJQQYMBYGCCsGAQUFBwMEBgorBgEEAYI3CgMMMCkGCSsG AQQBgjcVCgQcMBowCgYIKwYBBQUHAwQwDAYKKwYBBAGCNwoDDDBRBgNVHREESjBIoCoGCisGAQQB gjcUAgOgHAwaam9uYXRoYW4uZGVycmlja0BpbnRlbC5jb22BGmpvbmF0aGFuLmRlcnJpY2tAaW50 ZWwuY29tMA0GCSqGSIb3DQEBBQUAA4IBAQA5LNb+VnWY0V21FlNjnQ2BIb5gmlED29zwQiC5yezn 2SexgvN31129iJSkXuiBHdcVJiUAUPHYuxPRwumwbrkY6m+sYi9kIzKt+ZKNNAN4WbnavsbyRBlb cIn2E5swqD+sks8AmKivHmg+gFeboLaOf+EqVihIz1Wec1PpbX98R1t2ep7Y/81DD1fIjAWHl6Mq TJwjKQuYB01kkJdXZAGPXUQSARR1y2D1YpCkDqfGH2STaB4nenD4INSyhTGo5RV9wwTAibyrIq50 rnmvBnHTmICQVdHuIhG1gGmDLUAGqfrU3W2QJr9gkICdrTMgIEdd8s73wknaZxZKqfRxnMVQMYIC FzCCAhMCAQEwgZAweTELMAkGA1UEBhMCVVMxCzAJBgNVBAgTAkNBMRQwEgYDVQQHEwtTYW50YSBD bGFyYTEaMBgGA1UEChMRSW50ZWwgQ29ycG9yYXRpb24xKzApBgNVBAMTIkludGVsIEV4dGVybmFs IEJhc2ljIElzc3VpbmcgQ0EgNEECEzMAAKye+0C3syvSXOcAAAAArJ4wCQYFKw4DAhoFAKBdMBgG CSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTE4MDgxNjIwNTAzNVowIwYJ KoZIhvcNAQkEMRYEFGb/36pGlzDP2Ik8GJ30KKlszGiKMA0GCSqGSIb3DQEBAQUABIIBAKMHH3GJ uTSQFLVosV7cictpWbRRKsLIQJRwIuyik4iK1hLCYaOga4r4TgxrBd8hklzWsK7TTrOGG5gH8FXl byxM8R8dD+W6ve1J9OEPdUksgI56zVv/bdMyPr5caI8CyJh1C2E3BBaP7EnmF99NGM6HnTIMlnHB WEfLVPwupHtmvIoj+6SNZYFF9y307FBSK8W4Lv7Gd+ZfiV6qpj442r6wUXu3VOhP1NL/kpfSundo ITEFpTZG685ofkJsPK8j96OSyqQhL3ykK9+SXgL/gHml3o3bMGyuK+TR9xWwkoPcIBXLIelin5pG 8J6UQTBK/ZB5EKEKSyBgKBBCDKiFa2YAAAAAAAA= --=-Ak3dLlDYEWWixhmHkk0H--