debuggers.hg
changeset 22239:35a1a14c408e
Revert 22186:7167d6dd5c7c "x86: Retry do_mmu_update() a few times"
It does not work reliably for a couple of reasons:
(1) page_lock() fails if a page is !PGT_validated, and a page can
remain in that state for unbounded time.
(2) in the kernel-side race that motivated this patch, pgd_pin() can
lose to vmalloc_sync_all() -- pgd_pin() can try to chaneg a pmd page's
type to l2_pagetable while
vmalloc_sync_all()->set_pmd()->do_mmu_update() has it temporarily
pinned as writable. This is hard to fix on the Xen side.
Hence I give up on this approach, revert the patch, and settle for
kernel-side patching only.
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
It does not work reliably for a couple of reasons:
(1) page_lock() fails if a page is !PGT_validated, and a page can
remain in that state for unbounded time.
(2) in the kernel-side race that motivated this patch, pgd_pin() can
lose to vmalloc_sync_all() -- pgd_pin() can try to chaneg a pmd page's
type to l2_pagetable while
vmalloc_sync_all()->set_pmd()->do_mmu_update() has it temporarily
pinned as writable. This is hard to fix on the Xen side.
Hence I give up on this approach, revert the patch, and settle for
kernel-side patching only.
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
| author | Keir Fraser <keir.fraser@citrix.com> |
|---|---|
| date | Wed Sep 22 08:49:09 2010 +0100 (2010-09-22) |
| parents | a2b46be9958e |
| children | e8e3aeed3eba |
| files | xen/arch/x86/mm.c |
line diff
1.1 --- a/xen/arch/x86/mm.c Tue Sep 21 17:54:43 2010 +0100 1.2 +++ b/xen/arch/x86/mm.c Wed Sep 22 08:49:09 2010 +0100 1.3 @@ -3414,7 +3414,6 @@ int do_mmu_update( 1.4 case MMU_NORMAL_PT_UPDATE: 1.5 case MMU_PT_UPDATE_PRESERVE_AD: 1.6 { 1.7 - unsigned int retries = 0; 1.8 p2m_type_t p2mt; 1.9 1.10 rc = xsm_mmu_normal_update(d, pg_owner, req.val); 1.11 @@ -3446,7 +3445,6 @@ int do_mmu_update( 1.12 (unsigned long)(req.ptr & ~PAGE_MASK)); 1.13 page = mfn_to_page(mfn); 1.14 1.15 - retry: 1.16 if ( page_lock(page) ) 1.17 { 1.18 switch ( page->u.inuse.type_info & PGT_type_mask ) 1.19 @@ -3603,11 +3601,6 @@ int do_mmu_update( 1.20 v, va, req.val, _mfn(mfn)); 1.21 put_page_type(page); 1.22 } 1.23 - else if ( retries++ < 5 ) 1.24 - { 1.25 - /* Page type can be in flux, so we retry a few times. */ 1.26 - goto retry; 1.27 - } 1.28 1.29 unmap_domain_page_with_cache(va, &mapcache); 1.30 put_page(page);