>>> On 08.03.18 at 12:59, <jgr...@suse.com> wrote:
> On 05/03/18 17:43, Jan Beulich wrote:
>>>>> On 02.03.18 at 09:13, <jgr...@suse.com> wrote:
>>> @@ -3704,18 +3706,22 @@ long do_mmu_update(
>>> break;
>>> rc = mod_l4_entry(va, l4e_from_intpte(req.val), mfn,
>>> cmd == MMU_PT_UPDATE_PRESERVE_AD, v);
>>> - /*
>>> - * No need to sync if all uses of the page can be
>>> accounted
>>> - * to the page lock we hold, its pinned status, and
>>> uses on
>>> - * this (v)CPU.
>>> - */
>>> - if ( !rc && !cpu_has_no_xpti &&
>>> - ((page->u.inuse.type_info & PGT_count_mask) >
>>> - (1 + !!(page->u.inuse.type_info & PGT_pinned) +
>>> - (pagetable_get_pfn(curr->arch.guest_table) ==
>>> mfn)
>>> +
>>> - (pagetable_get_pfn(curr->arch.guest_table_user)
>>> ==
>>> - mfn))) )
>
> Is it really possible this code is running with the user page table
> being active on the current cpu? I think this test can be dropped.
I'm not sure I understand: The check above isn't for what is
active on a CPU, but for what references are being held.
_Installing_ a root page table into ->arch.guest_table{,_user}
is when a reference is being obtained, not _loading_ the table
into CR3. (In theory the above could be extended to also
check vCPU-s other than current, but one would need to deal
with races; obviously pausing the other vCPU-s of the domain
wouldn't be a good idea, but that would be one possible way.)
Jan
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