Mailing List Archive

On 15.07.2020 11:59, Jan Beulich wrote:
> The filling and cleaning up of v->arch.guest_table in new_guest_cr3()
> was apparently inconsistent so far: There was a type ref acquired
> unconditionally for the new top level page table, but the dropping of
> the old type ref was conditional upon !paging_mode_refcounts(). Mirror
> this also to arch_set_info_guest().
>
> Also move new_guest_cr3()'s #ifdef to around the function - both callers
> now get built only when CONFIG_PV, i.e. no need to retain a stub.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

While I've got an ack from Tim, I think I need either an ack from
Andrew or someone's R-b in order to commit this.

Thanks, Jan

> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1122,8 +1122,6 @@ int arch_set_info_guest(
>
> if ( !cr3_page )
> rc = -EINVAL;
> - else if ( paging_mode_refcounts(d) )
> - /* nothing */;
> else if ( cr3_page == v->arch.old_guest_table )
> {
> v->arch.old_guest_table = NULL;
> @@ -1144,8 +1142,7 @@ int arch_set_info_guest(
> case -ERESTART:
> break;
> case 0:
> - if ( !compat && !VM_ASSIST(d, m2p_strict) &&
> - !paging_mode_refcounts(d) )
> + if ( !compat && !VM_ASSIST(d, m2p_strict) )
> fill_ro_mpt(cr3_mfn);
> break;
> default:
> @@ -1166,7 +1163,7 @@ int arch_set_info_guest(
>
> if ( !cr3_page )
> rc = -EINVAL;
> - else if ( !paging_mode_refcounts(d) )
> + else
> {
> rc = get_page_type_preemptible(cr3_page, PGT_root_page_table);
> switch ( rc )
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -3149,9 +3149,9 @@ int vcpu_destroy_pagetables(struct vcpu
> return rc;
> }
>
> +#ifdef CONFIG_PV
> int new_guest_cr3(mfn_t mfn)
> {
> -#ifdef CONFIG_PV
> struct vcpu *curr = current;
> struct domain *d = curr->domain;
> int rc;
> @@ -3220,7 +3220,7 @@ int new_guest_cr3(mfn_t mfn)
>
> pv_destroy_ldt(curr); /* Unconditional TLB flush later. */
>
> - if ( !VM_ASSIST(d, m2p_strict) && !paging_mode_refcounts(d) )
> + if ( !VM_ASSIST(d, m2p_strict) )
> fill_ro_mpt(mfn);
> curr->arch.guest_table = pagetable_from_mfn(mfn);
> update_cr3(curr);
> @@ -3231,30 +3231,24 @@ int new_guest_cr3(mfn_t mfn)
> {
> struct page_info *page = mfn_to_page(old_base_mfn);
>
> - if ( paging_mode_refcounts(d) )
> - put_page(page);
> - else
> - switch ( rc = put_page_and_type_preemptible(page) )
> - {
> - case -EINTR:
> - case -ERESTART:
> - curr->arch.old_guest_ptpg = NULL;
> - curr->arch.old_guest_table = page;
> - curr->arch.old_guest_table_partial = (rc == -ERESTART);
> - rc = -ERESTART;
> - break;
> - default:
> - BUG_ON(rc);
> - break;
> - }
> + switch ( rc = put_page_and_type_preemptible(page) )
> + {
> + case -EINTR:
> + case -ERESTART:
> + curr->arch.old_guest_ptpg = NULL;
> + curr->arch.old_guest_table = page;
> + curr->arch.old_guest_table_partial = (rc == -ERESTART);
> + rc = -ERESTART;
> + break;
> + default:
> + BUG_ON(rc);
> + break;
> + }
> }
>
> return rc;
> -#else
> - ASSERT_UNREACHABLE();
> - return -EINVAL;
> -#endif
> }
> +#endif
>
> #ifdef CONFIG_PV
> static int vcpumask_to_pcpumask(
>
>