Messages in this thread | | | Date | Mon, 7 Feb 2022 11:02:28 +0100 | From | Janosch Frank <> | Subject | Re: [PATCH v7 04/17] KVM: s390: pv: refactor s390_reset_acc |
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On 2/4/22 16:53, Claudio Imbrenda wrote: > Refactor s390_reset_acc so that it can be reused in upcoming patches. > > We don't want to hold all the locks used in a walk_page_range for too > long, and the destroy page UVC does take some time to complete. > Therefore we quickly gather the pages to destroy, and then destroy them > without holding all the locks. > > The new refactored function optionally allows to return early without > completing if a fatal signal is pending (and return and appropriate > error code). Two wrappers are provided to call the new function. > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > (dropping Janosch's Ack because of major changes to the patch) > --- > arch/s390/include/asm/gmap.h | 36 +++++++++++++- > arch/s390/kvm/pv.c | 12 ++++- > arch/s390/mm/gmap.c | 95 +++++++++++++++++++++++++----------- > 3 files changed, 111 insertions(+), 32 deletions(-) > > diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h > index 746e18bf8984..2a913014f63c 100644 > --- a/arch/s390/include/asm/gmap.h > +++ b/arch/s390/include/asm/gmap.h > @@ -147,7 +147,41 @@ int gmap_mprotect_notify(struct gmap *, unsigned long start, > void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4], > unsigned long gaddr, unsigned long vmaddr); > int gmap_mark_unmergeable(void); > -void s390_reset_acc(struct mm_struct *mm); > void s390_remove_old_asce(struct gmap *gmap); > int s390_replace_asce(struct gmap *gmap); > +void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns); > +int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start, > + unsigned long end, int interruptible);
s/int/bool/ ?
> + > +/** > + * s390_uv_destroy_range - Destroy a range of pages in the given mm. > + * @mm the mm on which to operate on > + * @start the start of the range > + * @end the end of the range > + * > + * This call will call cond_sched, so it should not generate stalls, but it
This function will call ?
> + * will otherwise only return when it completed. > + */ > +static inline void s390_uv_destroy_range(struct mm_struct *mm, unsigned long start, > + unsigned long end) > +{ > + (void)__s390_uv_destroy_range(mm, start, end, 0); > +} > + > +/** > + * s390_uv_destroy_range_interruptibe - Destroy a range of pages in the
interruptible
> + * given mm, but stop when a fatal signal is received. > + * @mm the mm on which to operate on > + * @start the start of the range > + * @end the end of the range > + * > + * This call will call cond_sched, so it should not generate stalls. It > + * will return -EINTR if a fatal signal is received, or 0 if the whole range > + * has been destroyed. > + */ > +static inline int s390_uv_destroy_range_interruptible(struct mm_struct *mm, unsigned long start, > + unsigned long end) > +{ > + return __s390_uv_destroy_range(mm, start, end, 1); > +} > #endif /* _ASM_S390_GMAP_H */ > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c > index 3c59ef763dde..2ab22500e092 100644 > --- a/arch/s390/kvm/pv.c > +++ b/arch/s390/kvm/pv.c > @@ -12,6 +12,8 @@ > #include <asm/gmap.h> > #include <asm/uv.h> > #include <asm/mman.h> > +#include <linux/pagewalk.h> > +#include <linux/sched/mm.h> > #include "kvm-s390.h" > > int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc) > @@ -157,8 +159,14 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) > { > int cc; > > - /* make all pages accessible before destroying the guest */ > - s390_reset_acc(kvm->mm); > + /* > + * if the mm still has a mapping, make all its pages accessible > + * before destroying the guest > + */ > + if (mmget_not_zero(kvm->mm)) { > + s390_uv_destroy_range(kvm->mm, 0, TASK_SIZE); > + mmput(kvm->mm); > + } > > cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm), > UVC_CMD_DESTROY_SEC_CONF, rc, rrc); > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > index ce6cac4463f2..6eb5acb4be3d 100644 > --- a/arch/s390/mm/gmap.c > +++ b/arch/s390/mm/gmap.c > @@ -2676,44 +2676,81 @@ void s390_reset_cmma(struct mm_struct *mm) > } > EXPORT_SYMBOL_GPL(s390_reset_cmma); > > -/* > - * make inaccessible pages accessible again > - */ > -static int __s390_reset_acc(pte_t *ptep, unsigned long addr, > - unsigned long next, struct mm_walk *walk) > +#define DESTROY_LOOP_THRESHOLD 32 > + > +struct reset_walk_state { > + unsigned long next; > + unsigned long count; > + unsigned long pfns[DESTROY_LOOP_THRESHOLD]; > +}; > + > +static int s390_gather_pages(pte_t *ptep, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > { > + struct reset_walk_state *p = walk->private; > pte_t pte = READ_ONCE(*ptep); > > - /* There is a reference through the mapping */ > - if (pte_present(pte)) > - WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK)); > - > - return 0; > + if (pte_present(pte)) { > + /* we have a reference from the mapping, take an extra one */ > + get_page(phys_to_page(pte_val(pte))); > + p->pfns[p->count] = phys_to_pfn(pte_val(pte)); > + p->next = next; > + p->count++; > + } > + return p->count >= DESTROY_LOOP_THRESHOLD; > } > > -static const struct mm_walk_ops reset_acc_walk_ops = { > - .pte_entry = __s390_reset_acc, > +static const struct mm_walk_ops gather_pages_ops = { > + .pte_entry = s390_gather_pages, > }; > > -#include <linux/sched/mm.h> > -void s390_reset_acc(struct mm_struct *mm) > +/* > + * Call the Destroy secure page UVC on each page in the given array of PFNs. > + * Each page needs to have an extra reference, which will be released here. > + */ > +void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns) > { > - if (!mm_is_protected(mm)) > - return; > - /* > - * we might be called during > - * reset: we walk the pages and clear > - * close of all kvm file descriptors: we walk the pages and clear > - * exit of process on fd closure: vma already gone, do nothing > - */ > - if (!mmget_not_zero(mm)) > - return; > - mmap_read_lock(mm); > - walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL); > - mmap_read_unlock(mm); > - mmput(mm); > + unsigned long i; > + > + for (i = 0; i < count; i++) { > + /* we always have an extra reference */ > + uv_destroy_owned_page(pfn_to_phys(pfns[i])); > + /* get rid of the extra reference */ > + put_page(pfn_to_page(pfns[i])); > + cond_resched(); > + } > +} > +EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns); > + > +/** > + * __s390_uv_destroy_range - Walk the given range of the given address > + * space, and call the destroy secure page UVC on each page. > + * Optionally exit early if a fatal signal is pending. > + * @mm the mm to operate on > + * @start the start of the range > + * @end the end of the range > + * @interruptible if not 0, stop when a fatal signal is received > + * Return: 0 on success, -EINTR if the function stopped before completing > + */ > +int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start, > + unsigned long end, int interruptible) > +{ > + struct reset_walk_state state = { .next = start }; > + int r = 1; > + > + while (r > 0) { > + state.count = 0; > + mmap_read_lock(mm); > + r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state); > + mmap_read_unlock(mm); > + cond_resched(); > + s390_uv_destroy_pfns(state.count, state.pfns); > + if (interruptible && fatal_signal_pending(current)) > + return -EINTR; > + } > + return 0; > } > -EXPORT_SYMBOL_GPL(s390_reset_acc); > +EXPORT_SYMBOL_GPL(__s390_uv_destroy_range); > > /** > * s390_remove_old_asce - Remove the topmost level of page tables from the >
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