search for: u64_max

...ly from the vsyscall_gtod_data sequence to store the fact in a separate variable. That's inefficient. Restructure the code so the vclock readout returns cycles and the conversion to nanoseconds is handled at the call site. If the clock gets invalidated or vclock is already VCLOCK_NONE, return U64_MAX as the cycle value, which is invalid for all clocks and leave the sequence loop immediately in that case by calling the fallback function directly. This allows to remove the gettimeofday fallback as it now uses the clock_gettime() fallback and does the nanoseconds to microseconds conversion in the...

...we need to discard ReferenceTime and repeat > + * the whole sequence as the hypervisor was updating the page in > + * between. > + */ > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if (!sequence) > + break; It would be clearer to just return U64_MAX here (and not fall out) since this is only case here. Also since this failure only occurs if host clock is not available, probably should be unlikely. > + /* > + * Make sure we read sequence before we read other values from > + * TSC page. > + */ > + smp_rmb(); > + > +...

...we need to discard ReferenceTime and repeat > + * the whole sequence as the hypervisor was updating the page in > + * between. > + */ > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if (!sequence) > + break; It would be clearer to just return U64_MAX here (and not fall out) since this is only case here. Also since this failure only occurs if host clock is not available, probably should be unlikely. > + /* > + * Make sure we read sequence before we read other values from > + * TSC page. > + */ > + smp_rmb(); > + > +...

Hi, merge window is about to close so I hope it's OK to make another try here. Changes since v2: - Add explicit READ_ONCE() to not rely on 'volatile' [Andy Lutomirski] - rdtsc() -> rdtsc_ordered() [Andy Lutomirski] - virt_rmb() -> smp_rmb() [Thomas Gleixner, Andy Lutomirski] Thomas, Andy, it seems the only blocker for the series was the ambiguity with TSC page read algorithm.

Hi, merge window is about to close so I hope it's OK to make another try here. Changes since v2: - Add explicit READ_ONCE() to not rely on 'volatile' [Andy Lutomirski] - rdtsc() -> rdtsc_ordered() [Andy Lutomirski] - virt_rmb() -> smp_rmb() [Thomas Gleixner, Andy Lutomirski] Thomas, Andy, it seems the only blocker for the series was the ambiguity with TSC page read algorithm.

...s(&hv_syscore_ops); > > + if (hv_root_partition) > + hv_get_partition_id(); According to TLFS, partition ID is available when AccessPartitionId privilege is granted. I'd suggest we check that instead of hv_root_partition (and we can set hv_current_partition_id to something like U64_MAX so we know it wasn't acuired). So the BUG_ON condition will move here: hv_get_partition_id(); BUG_ON(hv_root_partition && hv_current_partition_id == U64_MAX); > + > return; > > remove_cpuhp_state: > diff --git a/arch/x86/include/asm/mshyperv.h b/arc...

On Wed, 3 Oct 2018, Andy Lutomirski wrote: > > On Oct 3, 2018, at 5:01 AM, Vitaly Kuznetsov <vkuznets at redhat.com> wrote: > > Not all Hyper-V hosts support reenlightenment notifications (and, if I'm > > not mistaken, you need to enable nesting for the VM to get the feature - > > and most VMs don't have this) so I think we'll have to keep Hyper-V >

....63dd00e 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -38,39 +38,11 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void) static u64 read_hv_clock_tsc(struct clocksource *arg) { - u64 current_tick; + u64 current_tick = hv_read_tsc_page(tsc_pg); + + if (current_tick == U64_MAX) + rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick); - if (tsc_pg->tsc_sequence != 0) { - /* - * Use the tsc page to compute the value. - */ - - while (1) { - u64 tmp; - u32 sequence = tsc_pg->tsc_sequence; - u64 cur_tsc; - u64 scale = tsc_pg->tsc_scale; - s64 offset = ts...

...; + > /* > * Zone resizing functions > * > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index ebdf6541d074..cfa0721280aa 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -98,11 +98,11 @@ void mem_hotplug_done(void) > u64 max_mem_size = U64_MAX; > > /* add this memory to iomem resource */ > -static struct resource *register_memory_resource(u64 start, u64 size) > +static struct resource *register_memory_resource(u64 start, u64 size, > + const char *resource_name) > { > struct resource *res; > unsigned...

...; + > /* > * Zone resizing functions > * > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index ebdf6541d074..cfa0721280aa 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -98,11 +98,11 @@ void mem_hotplug_done(void) > u64 max_mem_size = U64_MAX; > > /* add this memory to iomem resource */ > -static struct resource *register_memory_resource(u64 start, u64 size) > +static struct resource *register_memory_resource(u64 start, u64 size, > + const char *resource_name) > { > struct resource *res; > unsigned...

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() implementation, which extended the clockid switch case and added yet another slightly different copy of the same code. Especially the extended switch case is problematic as the compiler tends to generate a jump table which then requires to use retpolines. If jump tables are disabled it adds yet another conditional to the existing

...ver be able to observe time going backwards. > > > > I'll have a look into that. It needs some thought vs. the fractional part > > of the base time, but it should be not rocket science to get that > > correct. Famous last words... > > Does the sentinel need to be U64_MAX? What if vgetcyc and its minions > returned gtod->cycle_last-1 (for some value of 1), and the caller just > does "if ((s64)cycles - (s64)last < 0) return fallback; ns += > (cycles-last)* ...". That should just be a "sub ; js ; ". It's an extra > load of -&g...

...proc/iomem + */ +#define MHP_DRIVER_MANAGED 1 + /* * Zone resizing functions * diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index ebdf6541d074..cfa0721280aa 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -98,11 +98,11 @@ void mem_hotplug_done(void) u64 max_mem_size = U64_MAX; /* add this memory to iomem resource */ -static struct resource *register_memory_resource(u64 start, u64 size) +static struct resource *register_memory_resource(u64 start, u64 size, + const char *resource_name) { struct resource *res; unsigned long flags = IORESOURCE_SYSTEM_RAM | IO...

...functions > > * > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index ebdf6541d074..cfa0721280aa 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -98,11 +98,11 @@ void mem_hotplug_done(void) > > u64 max_mem_size = U64_MAX; > > > > /* add this memory to iomem resource */ > > -static struct resource *register_memory_resource(u64 start, u64 size) > > +static struct resource *register_memory_resource(u64 start, u64 size, > > + const char *resour...

> On Sep 18, 2018, at 12:52 AM, Thomas Gleixner <tglx at linutronix.de> wrote: > >> On Mon, 17 Sep 2018, John Stultz wrote: >>> On Mon, Sep 17, 2018 at 12:25 PM, Andy Lutomirski <luto at kernel.org> wrote: >>> Also, I'm not entirely convinced that this "last" thing is needed at >>> all. John, what's the scenario under which we

> On Sep 18, 2018, at 12:52 AM, Thomas Gleixner <tglx at linutronix.de> wrote: > >> On Mon, 17 Sep 2018, John Stultz wrote: >>> On Mon, Sep 17, 2018 at 12:25 PM, Andy Lutomirski <luto at kernel.org> wrote: >>> Also, I'm not entirely convinced that this "last" thing is needed at >>> all. John, what's the scenario under which we

Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() implementation, which extended the clockid switch case and added yet another slightly different copy of the same code. Especially the extended switch case is problematic as the compiler tends to generate a jump table which then requires to use retpolines. If jump tables are disabled it adds yet another conditional to the existing

Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() implementation, which extended the clockid switch case and added yet another slightly different copy of the same code. Especially the extended switch case is problematic as the compiler tends to generate a jump table which then requires to use retpolines. If jump tables are disabled it adds yet another conditional to the existing