I'd still vote for turning this into a "KVM: s390x: " patch or splitting
the gmap parts off.
> 8. Other capabilities.
> ----------------------
>
> diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
> index f5ff9dbad8ac..652cd658e242 100644
> --- a/arch/s390/include/asm/mmu.h
> +++ b/arch/s390/include/asm/mmu.h
> @@ -24,6 +24,8 @@ typedef struct {
> unsigned int uses_skeys:1;
> /* The mmu context uses CMM. */
> unsigned int uses_cmm:1;
> + /* The gmap associated with this context uses huge pages. */
> + unsigned int uses_gmap_hpage:1;
Didn't we discuss that something like "allow_gmap_1mb_hpage" or similar
would be more appropriate? The "uses" part can easily be wrong.
> #include <linux/kernel.h>
> @@ -589,8 +591,8 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
> return -EFAULT;
> pmd = pmd_offset(pud, vmaddr);
> VM_BUG_ON(pmd_none(*pmd));
> - /* large pmds cannot yet be handled */
> - if (pmd_large(*pmd))
> + /* Are we allowed to use huge pages? */
> + if (pmd_large(*pmd) && !gmap->mm->context.uses_gmap_hpage)
> return -EFAULT;
> /* Link gmap segment table entry location to page table. */
> rc = radix_tree_preload(GFP_KERNEL);
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index b6270a3b38e9..b955b986b341 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_GET_MSR_FEATURES 153
> #define KVM_CAP_HYPERV_EVENTFD 154
> #define KVM_CAP_HYPERV_TLBFLUSH 155
> +#define KVM_CAP_S390_HPAGE_1M 156
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
>
I was wondering if we should add some safety net for gmap shadows when
hitting a huge pmd. Or when trying to create a shadow for a gmap with
huge pmds enabled (add a check in gmap_shadow()). So the GMAP kernel
interface remains consistent.
Apart from that, looks good to me!
--
Thanks,
David / dhildenb
