[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH 1/2] x86: drop unnecessary page table walking in compat r/o M2P handling
We have a global variable where the necessary L2 table is recorded; no need to inspect L4 and L3 tables (and this way a few less places will eventually need adjustment when we want to support 5-level page tables). Also avoid setting up the L3 entry, as the address range never gets used anyway (it'll be dropped altogether in a subsequent patch). Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/x86_64/mm.c +++ b/xen/arch/x86/x86_64/mm.c @@ -219,9 +219,7 @@ static void destroy_compat_m2p_mapping(s { unsigned long i, va, rwva, pt_pfn; unsigned long smap = info->spfn, emap = info->spfn; - - l3_pgentry_t *l3_ro_mpt; - l2_pgentry_t *l2_ro_mpt; + l2_pgentry_t *l2_ro_mpt = compat_idle_pg_table_l2; if ( smap > ((RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2) ) return; @@ -229,12 +227,6 @@ static void destroy_compat_m2p_mapping(s if ( emap > ((RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2) ) emap = (RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2; - l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset(HIRO_COMPAT_MPT_VIRT_START)]); - - ASSERT(l3e_get_flags(l3_ro_mpt[l3_table_offset(HIRO_COMPAT_MPT_VIRT_START)]) & _PAGE_PRESENT); - - l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(HIRO_COMPAT_MPT_VIRT_START)]); - for ( i = smap; i < emap; ) { va = HIRO_COMPAT_MPT_VIRT_START + @@ -323,7 +315,6 @@ static int setup_compat_m2p_table(struct unsigned long i, va, smap, emap, rwva, epfn = info->epfn; mfn_t mfn; unsigned int n; - l3_pgentry_t *l3_ro_mpt = NULL; l2_pgentry_t *l2_ro_mpt = NULL; int err = 0; @@ -342,13 +333,7 @@ static int setup_compat_m2p_table(struct emap = ( (epfn + ((1UL << (L2_PAGETABLE_SHIFT - 2)) - 1 )) & ~((1UL << (L2_PAGETABLE_SHIFT - 2)) - 1) ); - va = HIRO_COMPAT_MPT_VIRT_START + - smap * sizeof(*compat_machine_to_phys_mapping); - l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]); - - ASSERT(l3e_get_flags(l3_ro_mpt[l3_table_offset(va)]) & _PAGE_PRESENT); - - l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]); + l2_ro_mpt = compat_idle_pg_table_l2; #define MFN(x) (((x) << L2_PAGETABLE_SHIFT) / sizeof(unsigned int)) #define CNT ((sizeof(*frame_table) & -sizeof(*frame_table)) / \ @@ -627,16 +612,10 @@ void __init paging_init(void) #undef MFN /* Create user-accessible L2 directory to map the MPT for compat guests. */ - BUILD_BUG_ON(l4_table_offset(RDWR_MPT_VIRT_START) != - l4_table_offset(HIRO_COMPAT_MPT_VIRT_START)); - l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset( - HIRO_COMPAT_MPT_VIRT_START)]); if ( (l2_ro_mpt = alloc_xen_pagetable()) == NULL ) goto nomem; compat_idle_pg_table_l2 = l2_ro_mpt; clear_page(l2_ro_mpt); - l3e_write(&l3_ro_mpt[l3_table_offset(HIRO_COMPAT_MPT_VIRT_START)], - l3e_from_paddr(__pa(l2_ro_mpt), __PAGE_HYPERVISOR_RO)); l2_ro_mpt += l2_table_offset(HIRO_COMPAT_MPT_VIRT_START); /* Allocate and map the compatibility mode machine-to-phys table. */ mpt_size = (mpt_size >> 1) + (1UL << (L2_PAGETABLE_SHIFT - 1));
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