Re: [PATCH v2 12/15] KVM: s390: move gmap_shadow_pgt_lookup() into kvm

[Janosch Frank <frankja@linux.ibm.com>]

On 1/16/25 12:33 PM, Claudio Imbrenda wrote:
> Move gmap_shadow_pgt_lookup() from mm/gmap.c into kvm/gaccess.c .
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   arch/s390/include/asm/gmap.h |  3 +--
>   arch/s390/kvm/gaccess.c      | 40 +++++++++++++++++++++++++++++++
>   arch/s390/kvm/gmap.h         |  2 ++
>   arch/s390/mm/gmap.c          | 46 ++----------------------------------
>   4 files changed, 45 insertions(+), 46 deletions(-)

[...]

>   
> +/**
> + * gmap_shadow_pgt_lookup - find a shadow page table

The other two VSIE functions in gaccess.c have the kvm_s390_shadow 
prefix but this one is only static anyway and hence we could just drop 
the gmap_ from the name.

> + * @sg: pointer to the shadow guest address space structure
> + * @saddr: the address in the shadow aguest address space
> + * @pgt: parent gmap address of the page table to get shadowed
> + * @dat_protection: if the pgtable is marked as protected by dat
> + * @fake: pgt references contiguous guest memory block, not a pgtable
> + *
> + * Returns 0 if the shadow page table was found and -EAGAIN if the page
> + * table was not found.
> + *
> + * Called with sg->mm->mmap_lock in read.
> + */
> +static int gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr, unsigned long *pgt,
> +				  int *dat_protection, int *fake)
> +{
> +	unsigned long *table;
> +	struct page *page;
> +	int rc;
> +
> +	spin_lock(&sg->guest_table_lock);
> +	table = gmap_table_walk(sg, saddr, 1); /* get segment pointer */

I'd be happy if you could introduce an enum for the level argument in a 
future series.

> +	if (table && !(*table & _SEGMENT_ENTRY_INVALID)) {
> +		/* Shadow page tables are full pages (pte+pgste) */
> +		page = pfn_to_page(*table >> PAGE_SHIFT);
> +		*pgt = page->index & ~GMAP_SHADOW_FAKE_TABLE;
> +		*dat_protection = !!(*table & _SEGMENT_ENTRY_PROTECT);
> +		*fake = !!(page->index & GMAP_SHADOW_FAKE_TABLE);
> +		rc = 0;
> +	} else  {
> +		rc = -EAGAIN;
> +	}
> +	spin_unlock(&sg->guest_table_lock);
> +	return rc;
> +}
> +
>