[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On 15/06/15 10:05, Ian Campbell wrote: > On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: >> xen_mm_pin_all()/unpin_all() are used to implement full guest instance >> suspend/restore. It's a stop-all method that needs to iterate through >> all allocated pgds in the system to fix them up for Xen's use. >> >> This code uses pgd_list, probably because it was an easy interface. >> >> But we want to remove the pgd_list, so convert the code over to walk >> all tasks in the system. This is an equivalent method. It is not equivalent because pgd_alloc() now populates entries in pgds that are not visible to xen_mm_pin_all() (note how the original code adds the pgd to the pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly allocated page tables won't be correctly converted on suspend/resume and the new process will die after resume. David >> >> (As I don't use Xen this is was only build tested.) > > In which case it seems extra important to copy the appropriate > maintainers, which I've done here. > > Ian. > >> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> >> Cc: Borislav Petkov <bp@xxxxxxxxx> >> Cc: Brian Gerst <brgerst@xxxxxxxxx> >> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> >> Cc: H. Peter Anvin <hpa@xxxxxxxxx> >> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> >> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> >> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> >> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >> Cc: Waiman Long <Waiman.Long@xxxxxx> >> Cc: linux-mm@xxxxxxxxx >> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> >> --- >> arch/x86/xen/mmu.c | 51 ++++++++++++++++++++++++++++++++++++++------------- >> 1 file changed, 38 insertions(+), 13 deletions(-) >> >> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c >> index dd151b2045b0..70a3df5b0b54 100644 >> --- a/arch/x86/xen/mmu.c >> +++ b/arch/x86/xen/mmu.c >> @@ -853,15 +853,27 @@ static void xen_pgd_pin(struct mm_struct *mm) >> */ >> void xen_mm_pin_all(void) >> { >> - struct page *page; >> + struct task_struct *g, *p; >> >> - spin_lock(&pgd_lock); >> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list >> iteration: */ >> >> - list_for_each_entry(page, &pgd_list, lru) { >> - if (!PagePinned(page)) { >> - __xen_pgd_pin(&init_mm, (pgd_t *)page_address(page)); >> - SetPageSavePinned(page); >> + for_each_process_thread(g, p) { >> + struct mm_struct *mm; >> + struct page *page; >> + pgd_t *pgd; >> + >> + task_lock(p); >> + mm = p->mm; >> + if (mm) { >> + pgd = mm->pgd; >> + page = virt_to_page(pgd); >> + >> + if (!PagePinned(page)) { >> + __xen_pgd_pin(&init_mm, pgd); >> + SetPageSavePinned(page); >> + } >> } >> + task_unlock(p); >> } >> >> spin_unlock(&pgd_lock); >> @@ -967,19 +979,32 @@ static void xen_pgd_unpin(struct mm_struct *mm) >> */ >> void xen_mm_unpin_all(void) >> { >> - struct page *page; >> + struct task_struct *g, *p; >> >> - spin_lock(&pgd_lock); >> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list >> iteration: */ >> >> - list_for_each_entry(page, &pgd_list, lru) { >> - if (PageSavePinned(page)) { >> - BUG_ON(!PagePinned(page)); >> - __xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page)); >> - ClearPageSavePinned(page); >> + for_each_process_thread(g, p) { >> + struct mm_struct *mm; >> + struct page *page; >> + pgd_t *pgd; >> + >> + task_lock(p); >> + mm = p->mm; >> + if (mm) { >> + pgd = mm->pgd; >> + page = virt_to_page(pgd); >> + >> + if (PageSavePinned(page)) { >> + BUG_ON(!PagePinned(page)); >> + __xen_pgd_unpin(&init_mm, pgd); >> + ClearPageSavePinned(page); >> + } >> } >> + task_unlock(p); >> } >> >> spin_unlock(&pgd_lock); >> + rcu_read_unlock(); >> } >> >> static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next) > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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