diff options
Diffstat (limited to 'arch/x86/xen/mmu.c')
| -rw-r--r-- | arch/x86/xen/mmu.c | 39 |
1 files changed, 33 insertions, 6 deletions
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 39ed56789f68..b65a76133f4f 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -308,8 +308,20 @@ static bool xen_batched_set_pte(pte_t *ptep, pte_t pteval) static inline void __xen_set_pte(pte_t *ptep, pte_t pteval) { - if (!xen_batched_set_pte(ptep, pteval)) - native_set_pte(ptep, pteval); + if (!xen_batched_set_pte(ptep, pteval)) { + /* + * Could call native_set_pte() here and trap and + * emulate the PTE write but with 32-bit guests this + * needs two traps (one for each of the two 32-bit + * words in the PTE) so do one hypercall directly + * instead. + */ + struct mmu_update u; + + u.ptr = virt_to_machine(ptep).maddr | MMU_NORMAL_PT_UPDATE; + u.val = pte_val_ma(pteval); + HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF); + } } static void xen_set_pte(pte_t *ptep, pte_t pteval) @@ -1416,13 +1428,28 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) } #endif /* CONFIG_X86_64 */ -/* Init-time set_pte while constructing initial pagetables, which - doesn't allow RO pagetable pages to be remapped RW */ +/* + * Init-time set_pte while constructing initial pagetables, which + * doesn't allow RO page table pages to be remapped RW. + * + * If there is no MFN for this PFN then this page is initially + * ballooned out so clear the PTE (as in decrease_reservation() in + * drivers/xen/balloon.c). + * + * Many of these PTE updates are done on unpinned and writable pages + * and doing a hypercall for these is unnecessary and expensive. At + * this point it is not possible to tell if a page is pinned or not, + * so always write the PTE directly and rely on Xen trapping and + * emulating any updates as necessary. + */ static void __init xen_set_pte_init(pte_t *ptep, pte_t pte) { - pte = mask_rw_pte(ptep, pte); + if (pte_mfn(pte) != INVALID_P2M_ENTRY) + pte = mask_rw_pte(ptep, pte); + else + pte = __pte_ma(0); - xen_set_pte(ptep, pte); + native_set_pte(ptep, pte); } static void pin_pagetable_pfn(unsigned cmd, unsigned long pfn) |