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Smith" , =?UTF-8?Q?Marek_Marczykowski-G=C3=B3recki?= , Jan Beulich , Julien Grall , Stefano Stabellini References: <20240913075907.34460-1-roger.pau@citrix.com> <20240913075907.34460-2-roger.pau@citrix.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: <20240913075907.34460-2-roger.pau@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 13/09/2024 8:59 am, Roger Pau Monne wrote: > diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc > index 959cf45b55d9..2a9b3b9b8975 100644 > --- a/docs/misc/xen-command-line.pandoc > +++ b/docs/misc/xen-command-line.pandoc > @@ -2816,6 +2816,27 @@ vwfi to `native` reduces irq latency significantly. It can also lead to > suboptimal scheduling decisions, but only when the system is > oversubscribed (i.e., in total there are more vCPUs than pCPUs). > > +### wallclock (x86) > +> `= auto | xen | cmos | efi` > + > +> Default: `auto` > + > +Allow forcing the usage of a specific wallclock source. > + > + * `auto` let the hypervisor select the clocksource based on internal > + heuristics. > + > + * `xen` force usage of the Xen shared_info wallclock when booted as a Xen > + guest. This option is only available if the hypervisor was compiled with > + `CONFIG_XEN_GUEST` enabled. > + > + * `cmos` force usage of the CMOS RTC wallclock. > + > + * `efi` force usage of the EFI_GET_TIME run-time method when booted from EFI > + firmware. For both `xen` and `efi`, something should be said about "if selected and not satisfied, Xen falls back to other heuristics". > + > +If the selected option is invalid or not available Xen will default to `auto`. I'm afraid that I'm firmly of the opinion that "auto" on the cmdline is unnecessary complexity.  Auto is the default, and doesn't need specifying explicitly.  That in turn simplifies ... > + > ### watchdog (x86) > > `= force | ` > > diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c > index 29b026735e5d..e4751684951e 100644 > --- a/xen/arch/x86/time.c > +++ b/xen/arch/x86/time.c > @@ -1552,6 +1552,37 @@ static const char *__init wallclock_type_to_string(void) > return ""; > } > > +static int __init cf_check parse_wallclock(const char *arg) > +{ > + wallclock_source = WALLCLOCK_UNSET; > + > + if ( !arg ) > + return -EINVAL; > + > + if ( !strcmp("auto", arg) ) > + ASSERT(wallclock_source == WALLCLOCK_UNSET); ... this. Hitting this assert will manifest as a system reboot/hang with no information on serial/VGA, because all of this runs prior to getting up the console.  You only get to see it on a PVH boot because we bodge the Xen console into default-existence. So, ASSERT()/etc really need avoiding wherever possible in cmdline parsing. In this case, all it serves to do is break examples like `wallclock=xen wallclock=auto` case, which is unlike our latest-takes-precedence behaviour everywhere else. > + else if ( !strcmp("xen", arg) ) > + { > + if ( !xen_guest ) We don't normally treat this path as an error when parsing (we know what it is, even if we can't action it).  Instead, there's no_config_param() to be more friendly (for PVH at least). It's a bit awkward, but this should do:     { #ifdef CONFIG_XEN_GUEST         wallclock_source = WALLCLOCK_XEN; #else         no_config_param("XEN_GUEST", "wallclock", s, ss); #endif     } There probably wants to be something similar for EFI, although it's not a plain CONFIG so it might be more tricky. ~Andrew