On Mon, 6 Sep 2021 18:16:10 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> On 06.09.21 17:56, Claudio Imbrenda wrote:
> > 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.
>
> Maybe add something like this to the patch description then.
>
> >>> +/*
> >>> + * 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);
>
> Do we have to protect against weird mappings without struct page here? I have not
> followed the discussion about this topic. Maybe Gerald knows if we can have memory
> without struct pages.
at first glance, it seems we can't have mappings without a struct page
>
> >>> + 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);
>
> Same here. If this is not an issue (and you add something to the patch description as
> outlined above)
>
> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>
>
