[PATCH] x86/cpa: make sure cpa is safe to call in lazy mmu mode

[PATCH] x86/cpa: make sure cpa is safe to call in lazy mmu mode

[Jeremy Fitzhardinge]

[ Ingo, this needs to go upstream and -stable. -J ]

commit 2193cee29f66b873b9f8ac2cebb2c7b755ec73a3
Author: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Date:   Tue Feb 10 14:15:52 2009 -0800

    x86/cpa: make sure cpa is safe to call in lazy mmu mode
    
    Impact: fix race leading to crash under KVM and Xen

    The CPA code may be called while we're in lazy mmu update mode - for
    example, when using DEBUG_PAGE_ALLOC and doing a slab allocation
    in an interrupt handler which interrupted a lazy mmu update.  In this
    case, the in-memory pagetable state may be out of date due to pending
    queued updates.  We need to flush any pending updates before inspecting
    the page table.  Similarly, we must explicitly flush any modifications
    CPA may have made (which comes down to flushing queued operations when
    flushing the TLB).
    
    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Acked-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 84ba748..fb12f06 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -576,6 +576,13 @@ static int __change_page_attr(struct cpa_data *cpa, int primary)
 	else
 		address = *cpa->vaddr;
 
+	/*
+	 * If we're called with lazy mmu updates enabled, the
+	 * in-memory pte state may be stale.  Flush pending updates to
+	 * bring them up to date.
+	 */
+	arch_flush_lazy_mmu_mode();
+
 repeat:
 	kpte = lookup_address(address, &level);
 	if (!kpte)
@@ -854,6 +861,13 @@ static int change_page_attr_set_clr(unsigned long *addr, int numpages,
 	} else
 		cpa_flush_all(cache);
 
+	/* 
+	 * If we've been called with lazy mmu updates enabled, then
+	 * make sure that everything gets flushed out before we
+	 * return.
+	 */
+	arch_flush_lazy_mmu_mode();
+
 out:
 	return ret;
 }

Re: [PATCH] x86/cpa: make sure cpa is safe to call in lazy mmu mode

[Ingo Molnar]

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> [ Ingo, this needs to go upstream and -stable. -J ]
>
> commit 2193cee29f66b873b9f8ac2cebb2c7b755ec73a3
> Author: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
> Date:   Tue Feb 10 14:15:52 2009 -0800
>
>    x86/cpa: make sure cpa is safe to call in lazy mmu mode
>       Impact: fix race leading to crash under KVM and Xen
>
>    The CPA code may be called while we're in lazy mmu update mode - for
>    example, when using DEBUG_PAGE_ALLOC and doing a slab allocation
>    in an interrupt handler which interrupted a lazy mmu update.  In this
>    case, the in-memory pagetable state may be out of date due to pending
>    queued updates.  We need to flush any pending updates before inspecting
>    the page table.  Similarly, we must explicitly flush any modifications
>    CPA may have made (which comes down to flushing queued operations when
>    flushing the TLB).
>       Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
>    Acked-by: Marcelo Tosatti <mtosatti@redhat.com>

applied to tip:x86/urgent, thanks Jeremy!

	Ingo