lguest: cache last cpu we ran on. (6d0cda93) · Commits · e / devices / android_kernel_fairphone_FP3

drivers/lguest/lg.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		struct pgdir {
		unsigned long gpgdir;
		bool switcher_mapped;
		int last_host_cpu;
		pgd_t *pgdir;
		};

drivers/lguest/page_tables.c

+53 −25

Original line number	Diff line number	Diff line
		@@ -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);
		/* Switcher page should always be mapped by now! */
		BUG_ON(!pgdir->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);

		/* 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.
		*