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. I gave up trying to figure out the MCE or power governor logic so we may have additional issues there. Additionally, flushtlb.c:34:DEFINE_PER_CPU(u32, tlbflush_time); really does need setting appropriately, although I think the only fallout is a few unnecessary TLB flushes. ~Andrew
