On Mon, 6 Sep 2021 17:46:40 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> On 18.08.21 15:26, Claudio Imbrenda wrote:
> > Introduce variants of the convert and destroy page functions that also
> > clear the PG_arch_1 bit used to mark them as secure pages.
> >
> > These new functions can only be called on pages for which a reference
> > is already being held.
> >
> > Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> > Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>
> Can you refresh my mind? We do have over-indication of PG_arch_1 and this
> might result in spending some unneeded cycles but in the end this will be
> correct. Right?
> And this patch will fix some unnecessary places that add overindication.
correct, PG_arch_1 will still overindicate, but with this patch it will
happen less.
And PG_arch_1 overindication is perfectly fine from a correctness point
of view.
> > ---
> > arch/s390/include/asm/pgtable.h | 9 ++++++---
> > arch/s390/include/asm/uv.h | 10 ++++++++--
> > arch/s390/kernel/uv.c | 34 ++++++++++++++++++++++++++++++++-
> > arch/s390/mm/gmap.c | 4 +++-
> > 4 files changed, 50 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> > index dcac7b2df72c..0f1af2232ebe 100644
> > --- a/arch/s390/include/asm/pgtable.h
> > +++ b/arch/s390/include/asm/pgtable.h
> > @@ -1074,8 +1074,9 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> > pte_t res;
> >
> > res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
> > + /* At this point the reference through the mapping is still present */
> > if (mm_is_protected(mm) && pte_present(res))
> > - uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> > + uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> > return res;
> > }
> >
> > @@ -1091,8 +1092,9 @@ static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
> > pte_t res;
> >
> > res = ptep_xchg_direct(vma->vm_mm, addr, ptep, __pte(_PAGE_INVALID));
> > + /* At this point the reference through the mapping is still present */
> > if (mm_is_protected(vma->vm_mm) && pte_present(res))
> > - uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> > + uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> > return res;
> > }
> >
> > @@ -1116,8 +1118,9 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
> > } else {
> > res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
> > }
> > + /* At this point the reference through the mapping is still present */
> > if (mm_is_protected(mm) && pte_present(res))
> > - uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> > + uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> > return res;
> > }
> >
> > diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> > index b35add51b967..3236293d5a31 100644
> > --- a/arch/s390/include/asm/uv.h
> > +++ b/arch/s390/include/asm/uv.h
> > @@ -356,8 +356,9 @@ static inline int is_prot_virt_host(void)
> > }
> >
> > int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
> > -int uv_destroy_page(unsigned long paddr);
> > +int uv_destroy_owned_page(unsigned long paddr);
> > int uv_convert_from_secure(unsigned long paddr);
> > +int uv_convert_owned_from_secure(unsigned long paddr);
> > int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
> >
> > void setup_uv(void);
> > @@ -367,7 +368,7 @@ void adjust_to_uv_max(unsigned long *vmax);
> > static inline void setup_uv(void) {}
> > static inline void adjust_to_uv_max(unsigned long *vmax) {}
> >
> > -static inline int uv_destroy_page(unsigned long paddr)
> > +static inline int uv_destroy_owned_page(unsigned long paddr)
> > {
> > return 0;
> > }
> > @@ -376,6 +377,11 @@ static inline int uv_convert_from_secure(unsigned long paddr)
> > {
> > return 0;
> > }
> > +
> > +static inline int uv_convert_owned_from_secure(unsigned long paddr)
> > +{
> > + return 0;
> > +}
> > #endif
> >
> > #if defined(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) || IS_ENABLED(CONFIG_KVM)
> > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> > index 68a8fbafcb9c..05f8bf61d20a 100644
> > --- a/arch/s390/kernel/uv.c
> > +++ b/arch/s390/kernel/uv.c
> > @@ -115,7 +115,7 @@ static int uv_pin_shared(unsigned long paddr)
> > *
> > * @paddr: Absolute host address of page to be destroyed
> > */
> > -int uv_destroy_page(unsigned long paddr)
> > +static int uv_destroy_page(unsigned long paddr)
> > {
> > struct uv_cb_cfs uvcb = {
> > .header.cmd = UVC_CMD_DESTR_SEC_STOR,
> > @@ -135,6 +135,22 @@ int uv_destroy_page(unsigned long paddr)
> > return 0;
> > }
> >
> > +/*
> > + * The caller must already hold a reference to the page
> > + */
> > +int uv_destroy_owned_page(unsigned long paddr)
> > +{
> > + struct page *page = phys_to_page(paddr);
> > + int rc;
> > +
> > + get_page(page);
> > + rc = uv_destroy_page(paddr);
> > + if (!rc)
> > + clear_bit(PG_arch_1, &page->flags);
> > + put_page(page);
> > + return rc;
> > +}
> > +
> > /*
> > * Requests the Ultravisor to encrypt a guest page and make it
> > * accessible to the host for paging (export).
> > @@ -154,6 +170,22 @@ int uv_convert_from_secure(unsigned long paddr)
> > return 0;
> > }
> >
> > +/*
> > + * The caller must already hold a reference to the page
> > + */
> > +int uv_convert_owned_from_secure(unsigned long paddr)
> > +{
> > + struct page *page = phys_to_page(paddr);
> > + int rc;
> > +
> > + get_page(page);
> > + rc = uv_convert_from_secure(paddr);
> > + if (!rc)
> > + clear_bit(PG_arch_1, &page->flags);
> > + put_page(page);
> > + return rc;
> > +}
> > +
> > /*
> > * Calculate the expected ref_count for a page that would otherwise have no
> > * further pins. This was cribbed from similar functions in other places in
> > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> > index 5a138f6220c4..38b792ab57f7 100644
> > --- a/arch/s390/mm/gmap.c
> > +++ b/arch/s390/mm/gmap.c
> > @@ -2678,8 +2678,10 @@ static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
> > {
> > pte_t pte = READ_ONCE(*ptep);
> >
> > + /* There is a reference through the mapping */
> > if (pte_present(pte))
> > - WARN_ON_ONCE(uv_destroy_page(pte_val(pte) & PAGE_MASK));
> > + WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
> > +
> > return 0;
> > }
> >
> >
