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Re: [Qemu-devel] [PATCH] translate-all: fix locking of TBs whose two pag
From: |
Emilio G. Cota |
Subject: |
Re: [Qemu-devel] [PATCH] translate-all: fix locking of TBs whose two pages share the same physical page |
Date: |
Wed, 27 Jun 2018 12:47:57 -0400 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Tue, Jun 26, 2018 at 19:28:19 -0700, Richard Henderson wrote:
> On 06/25/2018 09:31 AM, Emilio G. Cota wrote:
> > + } else if (page1 == page2) {
> > + page_lock(p1);
> > + if (ret_p2) {
> > + *ret_p2 = p1;
>
> I think you should set NULL here...
>
> > @@ -1623,7 +1641,7 @@ tb_link_page(TranslationBlock *tb, tb_page_addr_t
> > phys_pc,
> > tb = existing_tb;
> > }
> >
> > - if (p2) {
> > + if (p2 && p2 != p) {
> > page_unlock(p2);
>
> ... so that you need no change here.
> Otherwise it looks good.
I did that initially. However, note that if we do that then
the second page is not added to the list of pages for this
TB (via tb_page_add), which breaks the provided test case.
page_lock_pair(&p, phys_pc, &p2, phys_page2, 1);
tb_page_add(p, tb, 0, phys_pc & TARGET_PAGE_MASK);
if (p2) {
tb_page_add(p2, tb, 1, phys_page2);
} else {
tb->page_addr[1] = -1;
}
Regardless of whether p1 and p2 point to the same physical page,
the fact that the TB goes across two virtual pages should be
preserved, and in this case tb_page_add must be called twice.
Thanks,
Emilio