On Wed, Jun 11, 2014 at 12:58 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Wednesday 11 June 2014 12:33:30 Grant Likely wrote: >> On Tue, Jun 10, 2014 at 7:56 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >> > Il 10/06/2014 20:08, Peter Maydell ha scritto: >> > >> >> On 10 June 2014 18:04, Christopher Covington <cov@xxxxxxxxxxxxxx> wrote: >> >>> >> >>> On 06/10/2014 10:42 AM, Peter Maydell wrote: >> >>>> >> >>>> I just noticed that this doesn't mandate that the platform >> >>>> provides an RTC. As I understand it, the UEFI spec mandates >> >>>> that there's an RTC (could somebody more familiar with UEFI >> >>>> than me confirm/deny that?) so we should probably put one here. >> >>> >> >>> >> >>> Pardon my ignorance, but what exactly disqualifies Generic Timer >> >>> implementations from being used as Real Time Clocks? >> >> >> >> >> >> So my naive view was that an RTC actually had to have >> >> support for dealing with real (wall) clock time, ie >> >> knowing it's 2014 and not 1970. The generic timers are >> >> just timers. Or am I wrong and UEFI doesn't really >> >> require that? >> > >> > >> > The real-time clock provides four UEFI runtime services (GetTime, SetTime, >> > GetWakeupTime, SetWakeupTime). The spec says that you can return >> > EFI_DEVICE_ERROR from GetTime/SetTime if "the time could not be >> > retrieved/set due to a hardware error", but I don't think this is enough to >> > make these two optional. By comparison, GetWakeupTime/SetWakeupTime can >> > also return EFI_UNSUPPORTED. >> >> In practical terms, yes the VM needs to provide an RTC interface, but >> I don't think it needs to appear in this spec, even if the kernel >> accesses it directly. Portable images should use the UEFI service. > > It sounds like it should be in the spec then, if we want people building > portable images to include the efi-rtc driver. Fair enough. g. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
