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Message-ID: <20240507182515.0ce19da5@p-imbrenda.boeblingen.de.ibm.com>
Date: Tue, 7 May 2024 18:25:15 +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 07/10] s390/uv: convert uv_destroy_owned_page() to
uv_destroy_(folio|pte)()
On Fri, 12 Apr 2024 16:21:17 +0200
David Hildenbrand <david@...hat.com> wrote:
> Let's have the following variants for destroying pages:
>
> (1) uv_destroy(): Like uv_pin_shared() and uv_convert_from_secure(),
> "low level" helper that operates on paddr and doesn't mess with folios.
>
> (2) uv_destroy_folio(): Consumes a folio to which we hold a reference.
>
> (3) uv_destroy_pte(): Consumes a PTE that holds a reference through the
> mapping.
>
> Unfortunately we need uv_destroy_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 | 2 +-
> arch/s390/include/asm/uv.h | 10 ++++++++--
> arch/s390/kernel/uv.c | 24 +++++++++++++++++-------
> arch/s390/mm/gmap.c | 6 ++++--
> 4 files changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 60950e7a25f5..97e040617c29 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1199,7 +1199,7 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
> * The notifier should have destroyed all protected vCPUs at this
> * point, so the destroy should be successful.
> */
> - if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
> + if (full && !uv_destroy_pte(res))
> return res;
> /*
> * If something went wrong and the page could not be destroyed, or
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index d2205ff97007..a1bef30066ef 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -483,7 +483,8 @@ static inline int is_prot_virt_host(void)
> int uv_pin_shared(unsigned long paddr);
> 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_owned_page(unsigned long paddr);
> +int uv_destroy_folio(struct folio *folio);
> +int uv_destroy_pte(pte_t pte);
> int uv_convert_owned_from_secure(unsigned long paddr);
> int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
>
> @@ -497,7 +498,12 @@ static inline int uv_pin_shared(unsigned long paddr)
> return 0;
> }
>
> -static inline int uv_destroy_owned_page(unsigned long paddr)
> +static inline int uv_destroy_folio(struct folio *folio)
> +{
> + return 0;
> +}
> +
> +static inline int uv_destroy_pte(pte_t pte)
> {
> return 0;
> }
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index 3d3250b406a6..61c1ce51c883 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -110,7 +110,7 @@ EXPORT_SYMBOL_GPL(uv_pin_shared);
> *
> * @paddr: Absolute host address of page to be destroyed
> */
> -static int uv_destroy_page(unsigned long paddr)
> +static int uv_destroy(unsigned long paddr)
> {
> struct uv_cb_cfs uvcb = {
> .header.cmd = UVC_CMD_DESTR_SEC_STOR,
> @@ -131,11 +131,10 @@ static int uv_destroy_page(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_destroy_owned_page(unsigned long paddr)
> +int uv_destroy_folio(struct folio *folio)
> {
> - struct folio *folio = phys_to_folio(paddr);
> int rc;
>
> /* See gmap_make_secure(): large folios cannot be secure */
> @@ -143,13 +142,22 @@ int uv_destroy_owned_page(unsigned long paddr)
> return 0;
>
> folio_get(folio);
> - rc = uv_destroy_page(paddr);
> + rc = uv_destroy(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_destroy_pte(pte_t pte)
> +{
> + VM_WARN_ON(!pte_present(pte));
> + return uv_destroy_folio(pfn_folio(pte_pfn(pte)));
> +}
> +
> /*
> * Requests the Ultravisor to encrypt a guest page and make it
> * accessible to the host for paging (export).
> @@ -437,6 +445,7 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
> {
> struct vm_area_struct *vma;
> unsigned long uaddr;
> + struct folio *folio;
> struct page *page;
> int rc;
>
> @@ -460,7 +469,8 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
> page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET);
> if (IS_ERR_OR_NULL(page))
> goto out;
> - rc = uv_destroy_owned_page(page_to_phys(page));
> + folio = page_folio(page);
> + rc = uv_destroy_folio(folio);
> /*
> * Fault handlers can race; it is possible that two CPUs will fault
> * on the same secure page. One CPU can destroy the page, reboot,
> @@ -472,7 +482,7 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
> */
> if (rc)
> rc = uv_convert_owned_from_secure(page_to_phys(page));
> - put_page(page);
> + folio_put(folio);
> out:
> mmap_read_unlock(gmap->mm);
> return rc;
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 094b43b121cd..0351cb139df4 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2756,13 +2756,15 @@ static const struct mm_walk_ops gather_pages_ops = {
> */
> void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
> {
> + struct folio *folio;
> unsigned long i;
>
> for (i = 0; i < count; i++) {
> + folio = pfn_folio(pfns[i]);
> /* we always have an extra reference */
> - uv_destroy_owned_page(pfn_to_phys(pfns[i]));
> + uv_destroy_folio(folio);
> /* get rid of the extra reference */
> - put_page(pfn_to_page(pfns[i]));
> + folio_put(folio);
> cond_resched();
> }
> }
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