Commit b7ff99ea authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: wire up pte_update/pte_update_defer 



Impact: intermittent guest segv/crash fix

I've been seeing random guest bad address crashes and segmentation faults:
bisect led to 4f98a2fe (vmscan: split LRU lists into anon & file sets),
but that's a red herring.

It turns out that lguest never hooked up the pte_update/pte_update_defer
calls, so our ptes were not always in sync.  After the vmscan commit, the
bug became reproducible; now a fsck in a 64MB guest causes reproducible
pagetable corruption.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: jeremy@xensource.com
Cc: virtualization@lists.osdl.org
Cc: stable@kernel.org
parent 6afbdd05

arch/x86/lguest/boot.c

+9 −1
Original line number Diff line number Diff line
@@ -490,11 +490,17 @@ static void lguest_write_cr4(unsigned long val) 
 * into a process' address space.  We set the entry then tell the Host the

 * toplevel and address this corresponds to.  The Guest uses one pagetable per

 * process, so we need to tell the Host which one we're changing (mm->pgd). */

static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,

			       pte_t *ptep)

{

	lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, ptep->pte_low);

}



static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,

			      pte_t *ptep, pte_t pteval)

{

	*ptep = pteval;

	lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, pteval.pte_low);

	lguest_pte_update(mm, addr, ptep);

}



/* The Guest calls this to set a top-level entry.  Again, we set the entry then
@@ -1040,6 +1046,8 @@ __init void lguest_init(void) 
	pv_mmu_ops.read_cr3 = lguest_read_cr3;

	pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu;

	pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mode;

	pv_mmu_ops.pte_update = lguest_pte_update;

	pv_mmu_ops.pte_update_defer = lguest_pte_update;



#ifdef CONFIG_X86_LOCAL_APIC

	/* apic read/write intercepts */

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