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Message-ID: <20240507182619.2846ea8f@p-imbrenda.boeblingen.de.ibm.com>
Date: Tue, 7 May 2024 18:26:19 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
Vasily
Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle
<svens@...ux.ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Gerald
Schaefer <gerald.schaefer@...ux.ibm.com>,
Matthew Wilcox
<willy@...radead.org>, Thomas Huth <thuth@...hat.com>
Subject: Re: [PATCH v2 08/10] s390/uv: convert
uv_convert_owned_from_secure() to uv_convert_from_secure_(folio|pte)()
On Fri, 12 Apr 2024 16:21:18 +0200
David Hildenbrand <david@...hat.com> wrote:
> Let's do the same as we did for uv_destroy_(folio|pte)() and
> have the following variants:
>
> (1) uv_convert_from_secure(): "low level" helper that operates on paddr
> and does not mess with folios.
>
> (2) uv_convert_from_secure_folio(): Consumes a folio to which we hold a
> reference.
>
> (3) uv_convert_from_secure_pte(): Consumes a PTE that holds a reference
> through the mapping.
>
> Unfortunately we need uv_convert_from_secure_pte(), because pfn_folio()
> and friends are not available in pgtable.h.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> ---
> arch/s390/include/asm/pgtable.h | 6 +++---
> arch/s390/include/asm/uv.h | 4 ++--
> arch/s390/kernel/uv.c | 18 +++++++++++++-----
> 3 files changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 97e040617c29..5ffc4828c25a 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1149,7 +1149,7 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> 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_owned_from_secure(pte_val(res) & PAGE_MASK);
> + uv_convert_from_secure_pte(res);
> return res;
> }
>
> @@ -1167,7 +1167,7 @@ static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
> 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_owned_from_secure(pte_val(res) & PAGE_MASK);
> + uv_convert_from_secure_pte(res);
> return res;
> }
>
> @@ -1206,7 +1206,7 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
> * if this is not a mm teardown, the slower export is used as
> * fallback instead.
> */
> - uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
> + uv_convert_from_secure_pte(res);
> return res;
> }
>
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index a1bef30066ef..0679445cac0b 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -485,7 +485,7 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
> int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr);
> int uv_destroy_folio(struct folio *folio);
> int uv_destroy_pte(pte_t pte);
> -int uv_convert_owned_from_secure(unsigned long paddr);
> +int uv_convert_from_secure_pte(pte_t pte);
> int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
>
> void setup_uv(void);
> @@ -508,7 +508,7 @@ static inline int uv_destroy_pte(pte_t pte)
> return 0;
> }
>
> -static inline int uv_convert_owned_from_secure(unsigned long paddr)
> +static inline int uv_convert_from_secure_pte(pte_t pte)
> {
> return 0;
> }
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index 61c1ce51c883..b456066d72da 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -178,11 +178,10 @@ static int uv_convert_from_secure(unsigned long paddr)
> }
>
> /*
> - * The caller must already hold a reference to the page
> + * The caller must already hold a reference to the folio.
> */
> -int uv_convert_owned_from_secure(unsigned long paddr)
> +static int uv_convert_from_secure_folio(struct folio *folio)
> {
> - struct folio *folio = phys_to_folio(paddr);
> int rc;
>
> /* See gmap_make_secure(): large folios cannot be secure */
> @@ -190,13 +189,22 @@ int uv_convert_owned_from_secure(unsigned long paddr)
> return 0;
>
> folio_get(folio);
> - rc = uv_convert_from_secure(paddr);
> + rc = uv_convert_from_secure(folio_to_phys(folio));
> if (!rc)
> clear_bit(PG_arch_1, &folio->flags);
> folio_put(folio);
> return rc;
> }
>
> +/*
> + * The present PTE still indirectly holds a folio reference through the mapping.
> + */
> +int uv_convert_from_secure_pte(pte_t pte)
> +{
> + VM_WARN_ON(!pte_present(pte));
> + return uv_convert_from_secure_folio(pfn_folio(pte_pfn(pte)));
> +}
> +
> /*
> * Calculate the expected ref_count for a folio that would otherwise have no
> * further pins. This was cribbed from similar functions in other places in
> @@ -481,7 +489,7 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
> * we instead try to export the page.
> */
> if (rc)
> - rc = uv_convert_owned_from_secure(page_to_phys(page));
> + rc = uv_convert_from_secure_folio(folio);
> folio_put(folio);
> out:
> mmap_read_unlock(gmap->mm);
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