diff options
| -rw-r--r-- | drivers/lguest/lg.h | 1 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 78 |
2 files changed, 54 insertions, 25 deletions
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 005929a3fd5..2eef40be4c0 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -17,6 +17,7 @@ struct pgdir { unsigned long gpgdir; bool switcher_mapped; + int last_host_cpu; pgd_t *pgdir; }; diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index d1a5de45be0..19611b0551c 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -7,7 +7,7 @@ * converted Guest pages when running the Guest. :*/ -/* Copyright (C) Rusty Russell IBM Corporation 2006. +/* Copyright (C) Rusty Russell IBM Corporation 2013. * GPL v2 and any later version */ #include <linux/mm.h> #include <linux/gfp.h> @@ -731,6 +731,9 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, /* Release all the non-kernel mappings. */ flush_user_mappings(cpu->lg, next); + /* This hasn't run on any CPU at all. */ + cpu->lg->pgdirs[next].last_host_cpu = -1; + return next; } @@ -790,6 +793,7 @@ static void release_all_pagetables(struct lguest *lg) for (j = 0; j < PTRS_PER_PGD; j++) release_pgd(lg->pgdirs[i].pgdir + j); lg->pgdirs[i].switcher_mapped = false; + lg->pgdirs[i].last_host_cpu = -1; } } @@ -1086,37 +1090,62 @@ void free_guest_pagetable(struct lguest *lg) free_page((long)lg->pgdirs[i].pgdir); } +/*H:481 + * This clears the Switcher mappings for cpu #i. + */ +static void remove_switcher_percpu_map(struct lg_cpu *cpu, unsigned int i) +{ + unsigned long base = switcher_addr + PAGE_SIZE + i * PAGE_SIZE*2; + pte_t *pte; + + /* Clear the mappings for both pages. */ + pte = find_spte(cpu, base, false, 0, 0); + release_pte(*pte); + set_pte(pte, __pte(0)); + + pte = find_spte(cpu, base + PAGE_SIZE, false, 0, 0); + release_pte(*pte); + set_pte(pte, __pte(0)); +} + /*H:480 * (vi) Mapping the Switcher when the Guest is about to run. * - * The Switcher and the two pages for this CPU need to be visible in the - * Guest (and not the pages for other CPUs). + * The Switcher and the two pages for this CPU need to be visible in the Guest + * (and not the pages for other CPUs). * - * The pages have all been allocate + * The pages for the pagetables have all been allocated before: we just need + * to make sure the actual PTEs are up-to-date for the CPU we're about to run + * on. */ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) { - unsigned long base, i; + unsigned long base; struct page *percpu_switcher_page, *regs_page; pte_t *pte; + struct pgdir *pgdir = &cpu->lg->pgdirs[cpu->cpu_pgd]; - /* Switcher page should always be mapped! */ - BUG_ON(!cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped); - - /* Clear all the Switcher mappings for any other CPUs. */ - /* FIXME: This is dumb: update only when Host CPU changes. */ - for_each_possible_cpu(i) { - /* Get location of lguest_pages (indexed by Host CPU) */ - base = switcher_addr + PAGE_SIZE - + i * sizeof(struct lguest_pages); + /* Switcher page should always be mapped by now! */ + BUG_ON(!pgdir->switcher_mapped); - /* Get shadow PTE for first page (where we put guest regs). */ - pte = find_spte(cpu, base, false, 0, 0); - set_pte(pte, __pte(0)); + /* + * Remember that we have two pages for each Host CPU, so we can run a + * Guest on each CPU without them interfering. We need to make sure + * those pages are mapped correctly in the Guest, but since we usually + * run on the same CPU, we cache that, and only update the mappings + * when we move. + */ + if (pgdir->last_host_cpu == raw_smp_processor_id()) + return; - /* This is where we put R/O state. */ - pte = find_spte(cpu, base + PAGE_SIZE, false, 0, 0); - set_pte(pte, __pte(0)); + /* -1 means unknown so we remove everything. */ + if (pgdir->last_host_cpu == -1) { + unsigned int i; + for_each_possible_cpu(i) + remove_switcher_percpu_map(cpu, i); + } else { + /* We know exactly what CPU mapping to remove. */ + remove_switcher_percpu_map(cpu, pgdir->last_host_cpu); } /* @@ -1140,18 +1169,17 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) * the Guest: the IDT, GDT and other things it's not supposed to * change. */ - base += PAGE_SIZE; - pte = find_spte(cpu, base, false, 0, 0); - + pte = find_spte(cpu, base + PAGE_SIZE, false, 0, 0); percpu_switcher_page = lg_switcher_pages[1 + raw_smp_processor_id()*2 + 1]; get_page(percpu_switcher_page); set_pte(pte, mk_pte(percpu_switcher_page, __pgprot(__PAGE_KERNEL_RO & ~_PAGE_GLOBAL))); + + pgdir->last_host_cpu = raw_smp_processor_id(); } -/*:*/ -/* +/*H:490 * We've made it through the page table code. Perhaps our tired brains are * still processing the details, or perhaps we're simply glad it's over. * |