On Mon, Oct 18, 2021 at 10:21:28AM +0200, Jan Beulich wrote: > On 24.08.2021 23:11, Andrew Cooper wrote: > > On 18/08/2021 13:44, Andrew Cooper wrote: > >> On 18/08/2021 12:30, Marek Marczykowski-Górecki wrote: > >>> set_xcr0() and set_msr_xss() use cached value to avoid setting the > >>> register to the same value over and over. But suspend/resume implicitly > >>> reset the registers and since percpu areas are not deallocated on > >>> suspend anymore, the cache gets stale. > >>> Reset the cache on resume, to ensure the next write will really hit the > >>> hardware. Choose value 0, as it will never be a legitimate write to > >>> those registers - and so, will force write (and cache update). > >>> > >>> Note the cache is used io get_xcr0() and get_msr_xss() too, but: > >>> - set_xcr0() is called few lines below in xstate_init(), so it will > >>> update the cache with appropriate value > >>> - get_msr_xss() is not used anywhere - and thus not before any > >>> set_msr_xss() that will fill the cache > >>> > >>> Fixes: aca2a985a55a "xen: don't free percpu areas during suspend" > >>> Signed-off-by: Marek Marczykowski-Górecki > >>> <[email protected]> > >> I'd prefer to do this differently. As I said in the thread, there are > >> other registers such as MSR_TSC_AUX which fall into the same category, > >> and I'd like to make something which works systematically. > > > > Ok - after some searching, I think we have problems with: > > > > cpu/common.c:47:DEFINE_PER_CPU(struct cpuidmasks, cpuidmasks); > > cpu/common.c:120:static DEFINE_PER_CPU(uint64_t, msr_misc_features); > > msr.c:35:DEFINE_PER_CPU(uint32_t, tsc_aux); > > xstate.c:36:static DEFINE_PER_CPU(uint64_t, xcr0); > > xstate.c:79:static DEFINE_PER_CPU(uint64_t, xss); > > > > There is also: > > > > traps.c:100:DEFINE_PER_CPU(uint64_t, efer); > > > > which we *almost* handle correctly, but fail to update the cache on the > > BSP out of S3. > > > > > > For the APIC, I think we have issues with: > > > > irq.c:1083:static DEFINE_PER_CPU(struct pending_eoi, > > pending_eoi[NR_DYNAMIC_VECTORS]); > > > > because we don't defer S3 until all pending EOIs are complete. > > As your planned more extensive rework appears to not have made much > progress yet, may I suggest that we go with Marek's fix for 4.16, > with the one adjustment I suggested alongside giving my R-b?
I think that's the only viable solution in order to avoid shipping a broken 4.16 so we should go ahead with it. Thanks, Roger.
