| Message ID | 1454343998-26294-2-git-send-email-david.vrabel@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> From: David Vrabel [mailto:david.vrabel@citrix.com] > Sent: Tuesday, February 02, 2016 12:27 AM > > Holding the p2m lock while calling ept_sync_domain() is very expensive > since it does a on_selected_cpus() call. IPIs on many socket machines > can be very slows and on_selected_cpus() is serialized. slows -> slow > > It is safe to defer the invalidate until the p2m lock is released > except for two cases: > > 1. When freeing a page table page (since partial translations may be > cached). > 2. When reclaiming a zero page as part of PoD. > > For these cases, add p2m_tlb_flush_sync() calls which will immediately > perform the invalidate before the page is freed or reclaimed. > > Signed-off-by: David Vrabel <david.vrabel@citrix.com> [...] > diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c > index c094320..43c7f1b 100644 > --- a/xen/arch/x86/mm/p2m-ept.c > +++ b/xen/arch/x86/mm/p2m-ept.c > @@ -263,6 +263,7 @@ static void ept_free_entry(struct p2m_domain *p2m, ept_entry_t > *ept_entry, int l > unmap_domain_page(epte); > } > > + p2m_tlb_flush_sync(p2m); > p2m_free_ptp(p2m, mfn_to_page(ept_entry->mfn)); > } > > @@ -1095,15 +1096,10 @@ static void __ept_sync_domain(void *info) > */ > } > > -void ept_sync_domain(struct p2m_domain *p2m) > +static void ept_sync_domain_prepare(struct p2m_domain *p2m) > { > struct domain *d = p2m->domain; > struct ept_data *ept = &p2m->ept; > - /* Only if using EPT and this domain has some VCPUs to dirty. */ > - if ( !paging_mode_hap(d) || !d->vcpu || !d->vcpu[0] ) > - return; > - > - ASSERT(local_irq_is_enabled()); > > if ( nestedhvm_enabled(d) && !p2m_is_nestedp2m(p2m) ) > p2m_flush_nestedp2m(d); should we postpone nestedp2m flush similarly, which also incurs on_selected_cpus when holding p2m lock? > @@ -1116,9 +1112,38 @@ void ept_sync_domain(struct p2m_domain *p2m) > * of an EP4TA reuse is still needed. > */ > cpumask_setall(ept->invalidate); > +} > + > +static void ept_sync_domain_mask(struct p2m_domain *p2m, const cpumask_t *mask) > +{ > + on_selected_cpus(mask, __ept_sync_domain, p2m, 1); > +} > + > +void ept_sync_domain(struct p2m_domain *p2m) > +{ > + struct domain *d = p2m->domain; > > - on_selected_cpus(d->domain_dirty_cpumask, > - __ept_sync_domain, p2m, 1); > + /* Only if using EPT and this domain has some VCPUs to dirty. */ > + if ( !paging_mode_hap(d) || !d->vcpu || !d->vcpu[0] ) > + return; > + > + ept_sync_domain_prepare(p2m); > + > + if ( p2m->defer_flush ) > + { > + p2m->need_flush = 1; > + return; > + } > + > + ept_sync_domain_mask(p2m, d->domain_dirty_cpumask); > +} > + > +static void ept_flush_and_unlock(struct p2m_domain *p2m, bool_t unlock) > +{ > + p2m->need_flush = 0; > + if ( unlock ) > + mm_write_unlock(&p2m->lock); > + ept_sync_domain_mask(p2m, p2m->domain->domain_dirty_cpumask); > } > > static void ept_enable_pml(struct p2m_domain *p2m) > @@ -1169,6 +1194,7 @@ int ept_p2m_init(struct p2m_domain *p2m) > p2m->change_entry_type_range = ept_change_entry_type_range; > p2m->memory_type_changed = ept_memory_type_changed; > p2m->audit_p2m = NULL; > + p2m->flush_and_unlock = ept_flush_and_unlock; > > /* Set the memory type used when accessing EPT paging structures. */ > ept->ept_mt = EPT_DEFAULT_MT; > diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c > index ea16d3e..35835d1 100644 > --- a/xen/arch/x86/mm/p2m-pod.c > +++ b/xen/arch/x86/mm/p2m-pod.c > @@ -626,6 +626,7 @@ p2m_pod_decrease_reservation(struct domain *d, > > p2m_set_entry(p2m, gpfn + i, _mfn(INVALID_MFN), cur_order, > p2m_invalid, p2m->default_access); > + p2m_tlb_flush_sync(p2m); > for ( j = 0; j < n; ++j ) > set_gpfn_from_mfn(mfn_x(mfn), INVALID_M2P_ENTRY); > p2m_pod_cache_add(p2m, page, cur_order); > @@ -755,6 +756,7 @@ p2m_pod_zero_check_superpage(struct p2m_domain *p2m, > unsigned long gfn) > /* Try to remove the page, restoring old mapping if it fails. */ > p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), PAGE_ORDER_2M, > p2m_populate_on_demand, p2m->default_access); > + p2m_tlb_flush_sync(p2m); > > /* Make none of the MFNs are used elsewhere... for example, mapped > * via the grant table interface, or by qemu. Allow one refcount for > @@ -886,6 +888,8 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long > *gfns, int count) > } > } > > + p2m_tlb_flush_sync(p2m); > + > /* Now check each page for real */ > for ( i=0; i < count; i++ ) > { > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c > index a45ee35..36a8fb7 100644 > --- a/xen/arch/x86/mm/p2m.c > +++ b/xen/arch/x86/mm/p2m.c > @@ -325,6 +325,25 @@ void p2m_flush_hardware_cached_dirty(struct domain *d) > } > } > > +/* > + * Force a synchronous P2M TLB flush if a deferred flush is pending. > + * > + * Must be called with the p2m lock held. > + */ > +void p2m_tlb_flush_sync(struct p2m_domain *p2m) > +{ > + if ( p2m->need_flush ) > + p2m->flush_and_unlock(p2m, 0); > +} > + > +void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m) > +{ > + if ( p2m->need_flush ) > + p2m->flush_and_unlock(p2m, 1); > + else > + mm_write_unlock(&p2m->lock); > +} prefer to move general stuff into this function, then you could just keep a flush() callback, e.g.: void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m) { if ( p2m->need_flush ) { p2m->need_flush = 0; mm_write_unlock(&p2m->lock); p2m->flush(p2m); } else mm_write_unlock(&p2m->lock); } Same for p2m_tlb_flush_sync. Thanks Kevin
On 03/02/16 03:44, Tian, Kevin wrote: >> From: David Vrabel [mailto:david.vrabel@citrix.com] >> Sent: Tuesday, February 02, 2016 12:27 AM Looks like I forgot about this patch. >> It is safe to defer the invalidate until the p2m lock is released >> except for two cases: >> >> 1. When freeing a page table page (since partial translations may be >> cached). >> 2. When reclaiming a zero page as part of PoD. >> >> For these cases, add p2m_tlb_flush_sync() calls which will immediately >> perform the invalidate before the page is freed or reclaimed. >> >> Signed-off-by: David Vrabel <david.vrabel@citrix.com> > [...] >> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c >> index c094320..43c7f1b 100644 >> --- a/xen/arch/x86/mm/p2m-ept.c >> +++ b/xen/arch/x86/mm/p2m-ept.c >> @@ -263,6 +263,7 @@ static void ept_free_entry(struct p2m_domain *p2m, ept_entry_t >> *ept_entry, int l >> unmap_domain_page(epte); >> } >> >> + p2m_tlb_flush_sync(p2m); >> p2m_free_ptp(p2m, mfn_to_page(ept_entry->mfn)); >> } >> >> @@ -1095,15 +1096,10 @@ static void __ept_sync_domain(void *info) >> */ >> } >> >> -void ept_sync_domain(struct p2m_domain *p2m) >> +static void ept_sync_domain_prepare(struct p2m_domain *p2m) >> { >> struct domain *d = p2m->domain; >> struct ept_data *ept = &p2m->ept; >> - /* Only if using EPT and this domain has some VCPUs to dirty. */ >> - if ( !paging_mode_hap(d) || !d->vcpu || !d->vcpu[0] ) >> - return; >> - >> - ASSERT(local_irq_is_enabled()); >> >> if ( nestedhvm_enabled(d) && !p2m_is_nestedp2m(p2m) ) >> p2m_flush_nestedp2m(d); > > should we postpone nestedp2m flush similarly, which also incurs > on_selected_cpus when holding p2m lock? Possibly. I have not looked at the nestedp2m stuff as it wasn't a use case I cared about. I think any changes in this area could be done separately. >> --- a/xen/arch/x86/mm/p2m.c >> +++ b/xen/arch/x86/mm/p2m.c >> @@ -325,6 +325,25 @@ void p2m_flush_hardware_cached_dirty(struct domain *d) >> } >> } >> >> +/* >> + * Force a synchronous P2M TLB flush if a deferred flush is pending. >> + * >> + * Must be called with the p2m lock held. >> + */ >> +void p2m_tlb_flush_sync(struct p2m_domain *p2m) >> +{ >> + if ( p2m->need_flush ) >> + p2m->flush_and_unlock(p2m, 0); >> +} >> + >> +void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m) >> +{ >> + if ( p2m->need_flush ) >> + p2m->flush_and_unlock(p2m, 1); >> + else >> + mm_write_unlock(&p2m->lock); >> +} > > prefer to move general stuff into this function, then you could just > keep a flush() callback, e.g.: > > void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m) > { > if ( p2m->need_flush ) > { > p2m->need_flush = 0; > mm_write_unlock(&p2m->lock); > p2m->flush(p2m); > } > else > mm_write_unlock(&p2m->lock); > } > > Same for p2m_tlb_flush_sync. I'm sure there was a reason why I did it like this but I can't remember. Let me try your suggestion. David
diff --git a/xen/arch/x86/mm/mm-locks.h b/xen/arch/x86/mm/mm-locks.h index 8a40986..2e8747e 100644 --- a/xen/arch/x86/mm/mm-locks.h +++ b/xen/arch/x86/mm/mm-locks.h @@ -265,14 +265,21 @@ declare_mm_lock(altp2mlist) */ declare_mm_rwlock(altp2m); -#define p2m_lock(p) \ -{ \ - if ( p2m_is_altp2m(p) ) \ - mm_write_lock(altp2m, &(p)->lock); \ - else \ - mm_write_lock(p2m, &(p)->lock); \ -} -#define p2m_unlock(p) mm_write_unlock(&(p)->lock); +#define p2m_lock(p) \ + do { \ + if ( p2m_is_altp2m(p) ) \ + mm_write_lock(altp2m, &(p)->lock); \ + else \ + mm_write_lock(p2m, &(p)->lock); \ + (p)->defer_flush++; \ + } while (0) +#define p2m_unlock(p) \ + do { \ + if ( --(p)->defer_flush == 0 ) \ + p2m_tlb_flush_and_unlock(p); \ + else \ + mm_write_unlock(&(p)->lock); \ + } while (0) #define gfn_lock(p,g,o) p2m_lock(p) #define gfn_unlock(p,g,o) p2m_unlock(p) #define p2m_read_lock(p) mm_read_lock(p2m, &(p)->lock) diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c index c094320..43c7f1b 100644 --- a/xen/arch/x86/mm/p2m-ept.c +++ b/xen/arch/x86/mm/p2m-ept.c @@ -263,6 +263,7 @@ static void ept_free_entry(struct p2m_domain *p2m, ept_entry_t *ept_entry, int l unmap_domain_page(epte); } + p2m_tlb_flush_sync(p2m); p2m_free_ptp(p2m, mfn_to_page(ept_entry->mfn)); } @@ -1095,15 +1096,10 @@ static void __ept_sync_domain(void *info) */ } -void ept_sync_domain(struct p2m_domain *p2m) +static void ept_sync_domain_prepare(struct p2m_domain *p2m) { struct domain *d = p2m->domain; struct ept_data *ept = &p2m->ept; - /* Only if using EPT and this domain has some VCPUs to dirty. */ - if ( !paging_mode_hap(d) || !d->vcpu || !d->vcpu[0] ) - return; - - ASSERT(local_irq_is_enabled()); if ( nestedhvm_enabled(d) && !p2m_is_nestedp2m(p2m) ) p2m_flush_nestedp2m(d); @@ -1116,9 +1112,38 @@ void ept_sync_domain(struct p2m_domain *p2m) * of an EP4TA reuse is still needed. */ cpumask_setall(ept->invalidate); +} + +static void ept_sync_domain_mask(struct p2m_domain *p2m, const cpumask_t *mask) +{ + on_selected_cpus(mask, __ept_sync_domain, p2m, 1); +} + +void ept_sync_domain(struct p2m_domain *p2m) +{ + struct domain *d = p2m->domain; - on_selected_cpus(d->domain_dirty_cpumask, - __ept_sync_domain, p2m, 1); + /* Only if using EPT and this domain has some VCPUs to dirty. */ + if ( !paging_mode_hap(d) || !d->vcpu || !d->vcpu[0] ) + return; + + ept_sync_domain_prepare(p2m); + + if ( p2m->defer_flush ) + { + p2m->need_flush = 1; + return; + } + + ept_sync_domain_mask(p2m, d->domain_dirty_cpumask); +} + +static void ept_flush_and_unlock(struct p2m_domain *p2m, bool_t unlock) +{ + p2m->need_flush = 0; + if ( unlock ) + mm_write_unlock(&p2m->lock); + ept_sync_domain_mask(p2m, p2m->domain->domain_dirty_cpumask); } static void ept_enable_pml(struct p2m_domain *p2m) @@ -1169,6 +1194,7 @@ int ept_p2m_init(struct p2m_domain *p2m) p2m->change_entry_type_range = ept_change_entry_type_range; p2m->memory_type_changed = ept_memory_type_changed; p2m->audit_p2m = NULL; + p2m->flush_and_unlock = ept_flush_and_unlock; /* Set the memory type used when accessing EPT paging structures. */ ept->ept_mt = EPT_DEFAULT_MT; diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c index ea16d3e..35835d1 100644 --- a/xen/arch/x86/mm/p2m-pod.c +++ b/xen/arch/x86/mm/p2m-pod.c @@ -626,6 +626,7 @@ p2m_pod_decrease_reservation(struct domain *d, p2m_set_entry(p2m, gpfn + i, _mfn(INVALID_MFN), cur_order, p2m_invalid, p2m->default_access); + p2m_tlb_flush_sync(p2m); for ( j = 0; j < n; ++j ) set_gpfn_from_mfn(mfn_x(mfn), INVALID_M2P_ENTRY); p2m_pod_cache_add(p2m, page, cur_order); @@ -755,6 +756,7 @@ p2m_pod_zero_check_superpage(struct p2m_domain *p2m, unsigned long gfn) /* Try to remove the page, restoring old mapping if it fails. */ p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), PAGE_ORDER_2M, p2m_populate_on_demand, p2m->default_access); + p2m_tlb_flush_sync(p2m); /* Make none of the MFNs are used elsewhere... for example, mapped * via the grant table interface, or by qemu. Allow one refcount for @@ -886,6 +888,8 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long *gfns, int count) } } + p2m_tlb_flush_sync(p2m); + /* Now check each page for real */ for ( i=0; i < count; i++ ) { diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index a45ee35..36a8fb7 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -325,6 +325,25 @@ void p2m_flush_hardware_cached_dirty(struct domain *d) } } +/* + * Force a synchronous P2M TLB flush if a deferred flush is pending. + * + * Must be called with the p2m lock held. + */ +void p2m_tlb_flush_sync(struct p2m_domain *p2m) +{ + if ( p2m->need_flush ) + p2m->flush_and_unlock(p2m, 0); +} + +void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m) +{ + if ( p2m->need_flush ) + p2m->flush_and_unlock(p2m, 1); + else + mm_write_unlock(&p2m->lock); +} + mfn_t __get_gfn_type_access(struct p2m_domain *p2m, unsigned long gfn, p2m_type_t *t, p2m_access_t *a, p2m_query_t q, unsigned int *page_order, bool_t locked) diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h index fa46dd9..d1c4a41 100644 --- a/xen/include/asm-x86/p2m.h +++ b/xen/include/asm-x86/p2m.h @@ -262,6 +262,24 @@ struct p2m_domain { l1_pgentry_t new, unsigned int level); long (*audit_p2m)(struct p2m_domain *p2m); + /* + * P2M updates may require TLBs to be flushed (invalidated). + * + * If 'defer_flush' is set, flushes may be deferred by setting + * 'need_flush' and then flushing in 'flush_and_unlock()'. + * + * 'flush_and_unlock()' is only called if 'need_flush' is set. It + * must clear 'need_flush', call 'mm_write_unlock&p2m->lock)' if + * 'unlock' is true, and perform the flush. + * + * If a flush may be being deferred but an immediate flush is + * required (e.g., if a page is being freed to pool other than the + * domheap), call p2m_tlb_flush_sync(). + */ + void (*flush_and_unlock)(struct p2m_domain *p2m, bool_t unlock); + unsigned int defer_flush; + bool_t need_flush; + /* Default P2M access type for each page in the the domain: new pages, * swapped in pages, cleared pages, and pages that are ambiguously * retyped get this access type. See definition of p2m_access_t. */ @@ -353,6 +371,12 @@ static inline bool_t p2m_is_altp2m(const struct p2m_domain *p2m) #define p2m_get_pagetable(p2m) ((p2m)->phys_table) +/* + * Ensure any deferred p2m TLB flush has been completed on all VCPUs. + */ +void p2m_tlb_flush_sync(struct p2m_domain *p2m); +void p2m_tlb_flush_and_unlock(struct p2m_domain *p2m); + /**** p2m query accessors. They lock p2m_lock, and thus serialize * lookups wrt modifications. They _do not_ release the lock on exit. * After calling any of the variants below, caller needs to use
Holding the p2m lock while calling ept_sync_domain() is very expensive since it does a on_selected_cpus() call. IPIs on many socket machines can be very slows and on_selected_cpus() is serialized. It is safe to defer the invalidate until the p2m lock is released except for two cases: 1. When freeing a page table page (since partial translations may be cached). 2. When reclaiming a zero page as part of PoD. For these cases, add p2m_tlb_flush_sync() calls which will immediately perform the invalidate before the page is freed or reclaimed. Signed-off-by: David Vrabel <david.vrabel@citrix.com> --- v7: - Add some more p2m_tlb_flush_sync() calls to PoD. - More comments. v6: - Move p2m_tlb_flush_sync() to immediately before p2m_free_ptp(). It was called all the time otherwise. v5: - add p2m_tlb_flush_sync() and call it before freeing pgae table pages and reclaiming zeroed pod pages. v2: - use per-p2m list for deferred pages. - update synced_mask while holding write lock. --- xen/arch/x86/mm/mm-locks.h | 23 +++++++++++++++-------- xen/arch/x86/mm/p2m-ept.c | 42 ++++++++++++++++++++++++++++++++++-------- xen/arch/x86/mm/p2m-pod.c | 4 ++++ xen/arch/x86/mm/p2m.c | 19 +++++++++++++++++++ xen/include/asm-x86/p2m.h | 24 ++++++++++++++++++++++++ 5 files changed, 96 insertions(+), 16 deletions(-)