lguest: per-vcpu lguest pgdir management

this patch makes the pgdir management per-vcpu. The pgdirs pool
is still guest-wide (although it'll probably need to grow when we
are really executing more vcpus), but the pgdidx index is gone,
since it makes no sense anymore. Instead, we use a per-vcpu
index.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/hypercalls.c

@@ -62,7 +62,7 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
 		if (args->arg1)
 			guest_pagetable_clear_all(cpu);
 		else
-			guest_pagetable_flush_user(lg);
+			guest_pagetable_flush_user(cpu);
 		break;
 
 	/* All these calls simply pass the arguments through to the right

drivers/lguest/interrupts_and_traps.c

@@ -76,7 +76,7 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, int has_err)
 		virtstack = cpu->esp1;
 		ss = cpu->ss1;
 
-		origstack = gstack = guest_pa(lg, virtstack);
+		origstack = gstack = guest_pa(cpu, virtstack);
 		/* We push the old stack segment and pointer onto the new
 		 * stack: when the Guest does an "iret" back from the interrupt
 		 * handler the CPU will notice they're dropping privilege
@@ -88,7 +88,7 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, int has_err)
 		virtstack = cpu->regs->esp;
 		ss = cpu->regs->ss;
 
-		origstack = gstack = guest_pa(lg, virtstack);
+		origstack = gstack = guest_pa(cpu, virtstack);
 	}
 
 	/* Remember that we never let the Guest actually disable interrupts, so
@@ -323,7 +323,7 @@ void pin_stack_pages(struct lg_cpu *cpu)
 		 * start of the page after the kernel stack.  Subtract one to
 		 * get back onto the first stack page, and keep subtracting to
 		 * get to the rest of the stack pages. */
-		pin_page(lg, cpu->esp1 - 1 - i * PAGE_SIZE);
+		pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE);
 }
 
 /* Direct traps also mean that we need to know whenever the Guest wants to use

drivers/lguest/lg.h

@@ -57,6 +57,8 @@ struct lg_cpu {
 	unsigned long regs_page;
 	struct lguest_regs *regs;
 
+	int cpu_pgd; /* which pgd this cpu is currently using */
+
 	/* If a hypercall was asked for, this points to the arguments. */
 	struct hcall_args *hcall;
 	u32 next_hcall;
@@ -92,8 +94,6 @@ struct lguest
 	int changed;
 	struct lguest_pages *last_pages;
 
-	/* We keep a small number of these. */
-	u32 pgdidx;
 	struct pgdir pgdirs[4];
 
 	unsigned long noirq_start, noirq_end;
@@ -169,13 +169,13 @@ void free_guest_pagetable(struct lguest *lg);
 void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable);
 void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 i);
 void guest_pagetable_clear_all(struct lg_cpu *cpu);
-void guest_pagetable_flush_user(struct lguest *lg);
+void guest_pagetable_flush_user(struct lg_cpu *cpu);
 void guest_set_pte(struct lguest *lg, unsigned long gpgdir,
 		   unsigned long vaddr, pte_t val);
 void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);
-int demand_page(struct lguest *info, unsigned long cr2, int errcode);
-void pin_page(struct lguest *lg, unsigned long vaddr);
-unsigned long guest_pa(struct lguest *lg, unsigned long vaddr);
+int demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);
+void pin_page(struct lg_cpu *cpu, unsigned long vaddr);
+unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr);
 void page_table_guest_data_init(struct lguest *lg);
 
 /* <arch>/core.c: */

drivers/lguest/page_tables.c

@@ -94,10 +94,10 @@ static pte_t *spte_addr(struct lguest *lg, pgd_t spgd, unsigned long vaddr)
 
 /* These two functions just like the above two, except they access the Guest
  * page tables.  Hence they return a Guest address. */
-static unsigned long gpgd_addr(struct lguest *lg, unsigned long vaddr)
+static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
 {
 	unsigned int index = vaddr >> (PGDIR_SHIFT);
-	return lg->pgdirs[lg->pgdidx].gpgdir + index * sizeof(pgd_t);
+	return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t);
 }
 
 static unsigned long gpte_addr(struct lguest *lg,
@@ -200,22 +200,23 @@ static void check_gpgd(struct lguest *lg, pgd_t gpgd)
  *
  * If we fixed up the fault (ie. we mapped the address), this routine returns
  * true.  Otherwise, it was a real fault and we need to tell the Guest. */
-int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
+int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
 {
 	pgd_t gpgd;
 	pgd_t *spgd;
 	unsigned long gpte_ptr;
 	pte_t gpte;
 	pte_t *spte;
+	struct lguest *lg = cpu->lg;
 
 	/* First step: get the top-level Guest page table entry. */
-	gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t);
+	gpgd = lgread(lg, gpgd_addr(cpu, vaddr), pgd_t);
 	/* Toplevel not present?  We can't map it in. */
 	if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
 		return 0;
 
 	/* Now look at the matching shadow entry. */
-	spgd = spgd_addr(lg, lg->pgdidx, vaddr);
+	spgd = spgd_addr(lg, cpu->cpu_pgd, vaddr);
 	if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
 		/* No shadow entry: allocate a new shadow PTE page. */
 		unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
@@ -297,30 +298,30 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
  *
  * This is a quick version which answers the question: is this virtual address
  * mapped by the shadow page tables, and is it writable? */
-static int page_writable(struct lguest *lg, unsigned long vaddr)
+static int page_writable(struct lg_cpu *cpu, unsigned long vaddr)
 {
 	pgd_t *spgd;
 	unsigned long flags;
 
 	/* Look at the current top level entry: is it present? */
-	spgd = spgd_addr(lg, lg->pgdidx, vaddr);
+	spgd = spgd_addr(cpu->lg, cpu->cpu_pgd, vaddr);
 	if (!(pgd_flags(*spgd) & _PAGE_PRESENT))
 		return 0;
 
 	/* Check the flags on the pte entry itself: it must be present and
 	 * writable. */
-	flags = pte_flags(*(spte_addr(lg, *spgd, vaddr)));
+	flags = pte_flags(*(spte_addr(cpu->lg, *spgd, vaddr)));
 
 	return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
 }
 
 /* So, when pin_stack_pages() asks us to pin a page, we check if it's already
  * in the page tables, and if not, we call demand_page() with error code 2
  * (meaning "write"). */
-void pin_page(struct lguest *lg, unsigned long vaddr)
+void pin_page(struct lg_cpu *cpu, unsigned long vaddr)
 {
-	if (!page_writable(lg, vaddr) && !demand_page(lg, vaddr, 2))
-		kill_guest(lg, "bad stack page %#lx", vaddr);
+	if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))
+		kill_guest(cpu->lg, "bad stack page %#lx", vaddr);
 }
 
 /*H:450 If we chase down the release_pgd() code, it looks like this: */
@@ -358,28 +359,28 @@ static void flush_user_mappings(struct lguest *lg, int idx)
  *
  * The Guest has a hypercall to throw away the page tables: it's used when a
  * large number of mappings have been changed. */
-void guest_pagetable_flush_user(struct lguest *lg)
+void guest_pagetable_flush_user(struct lg_cpu *cpu)
 {
 	/* Drop the userspace part of the current page table. */
-	flush_user_mappings(lg, lg->pgdidx);
+	flush_user_mappings(cpu->lg, cpu->cpu_pgd);
 }
 /*:*/
 
 /* We walk down the guest page tables to get a guest-physical address */
-unsigned long guest_pa(struct lguest *lg, unsigned long vaddr)
+unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
 {
 	pgd_t gpgd;
 	pte_t gpte;
 
 	/* First step: get the top-level Guest page table entry. */
-	gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t);
+	gpgd = lgread(cpu->lg, gpgd_addr(cpu, vaddr), pgd_t);
 	/* Toplevel not present?  We can't map it in. */
 	if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
-		kill_guest(lg, "Bad address %#lx", vaddr);
+		kill_guest(cpu->lg, "Bad address %#lx", vaddr);
 
-	gpte = lgread(lg, gpte_addr(lg, gpgd, vaddr), pte_t);
+	gpte = lgread(cpu->lg, gpte_addr(cpu->lg, gpgd, vaddr), pte_t);
 	if (!(pte_flags(gpte) & _PAGE_PRESENT))
-		kill_guest(lg, "Bad address %#lx", vaddr);
+		kill_guest(cpu->lg, "Bad address %#lx", vaddr);
 
 	return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
 }
@@ -399,11 +400,12 @@ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
 /*H:435 And this is us, creating the new page directory.  If we really do
  * allocate a new one (and so the kernel parts are not there), we set
  * blank_pgdir. */
-static unsigned int new_pgdir(struct lguest *lg,
+static unsigned int new_pgdir(struct lg_cpu *cpu,
 			      unsigned long gpgdir,
 			      int *blank_pgdir)
 {
 	unsigned int next;
+	struct lguest *lg = cpu->lg;
 
 	/* We pick one entry at random to throw out.  Choosing the Least
 	 * Recently Used might be better, but this is easy. */
@@ -413,7 +415,7 @@ static unsigned int new_pgdir(struct lguest *lg,
 		lg->pgdirs[next].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL);
 		/* If the allocation fails, just keep using the one we have */
 		if (!lg->pgdirs[next].pgdir)
-			next = lg->pgdidx;
+			next = cpu->cpu_pgd;
 		else
 			/* This is a blank page, so there are no kernel
 			 * mappings: caller must map the stack! */
@@ -442,9 +444,9 @@ void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
 	/* If not, we allocate or mug an existing one: if it's a fresh one,
 	 * repin gets set to 1. */
 	if (newpgdir == ARRAY_SIZE(lg->pgdirs))
-		newpgdir = new_pgdir(lg, pgtable, &repin);
+		newpgdir = new_pgdir(cpu, pgtable, &repin);
 	/* Change the current pgd index to the new one. */
-	lg->pgdidx = newpgdir;
+	cpu->cpu_pgd = newpgdir;
 	/* If it was completely blank, we map in the Guest kernel stack */
 	if (repin)
 		pin_stack_pages(cpu);
@@ -591,11 +593,11 @@ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable)
 {
 	/* We start on the first shadow page table, and give it a blank PGD
 	 * page. */
-	lg->pgdidx = 0;
-	lg->pgdirs[lg->pgdidx].gpgdir = pgtable;
-	lg->pgdirs[lg->pgdidx].pgdir = (pgd_t*)get_zeroed_page(GFP_KERNEL);
-	if (!lg->pgdirs[lg->pgdidx].pgdir)
+	lg->pgdirs[0].gpgdir = pgtable;
+	lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL);
+	if (!lg->pgdirs[0].pgdir)
 		return -ENOMEM;
+	lg->cpus[0].cpu_pgd = 0;
 	return 0;
 }
 
@@ -607,7 +609,7 @@ void page_table_guest_data_init(struct lguest *lg)
 	    /* We tell the Guest that it can't use the top 4MB of virtual
 	     * addresses used by the Switcher. */
 	    || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)
-	    || put_user(lg->pgdirs[lg->pgdidx].gpgdir,&lg->lguest_data->pgdir))
+	    || put_user(lg->pgdirs[0].gpgdir, &lg->lguest_data->pgdir))
 		kill_guest(lg, "bad guest page %p", lg->lguest_data);
 
 	/* In flush_user_mappings() we loop from 0 to
@@ -637,7 +639,6 @@ void free_guest_pagetable(struct lguest *lg)
  * Guest is about to run on this CPU. */
 void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
 {
-	struct lguest *lg = cpu->lg;
 	pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
 	pgd_t switcher_pgd;
 	pte_t regs_pte;
@@ -647,7 +648,7 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
 	 * page for this CPU (with appropriate flags). */
 	switcher_pgd = __pgd(__pa(switcher_pte_page) | _PAGE_KERNEL);
 
-	lg->pgdirs[lg->pgdidx].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
+	cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
 
 	/* We also change the Switcher PTE page.  When we're running the Guest,
 	 * we want the Guest's "regs" page to appear where the first Switcher

drivers/lguest/x86/core.c

@@ -145,7 +145,7 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
 		      * 0-th argument above, ie "a").  %ebx contains the
 		      * physical address of the Guest's top-level page
 		      * directory. */
-		     : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
+		     : "0"(pages), "1"(__pa(lg->pgdirs[cpu->cpu_pgd].pgdir))
 		     /* We tell gcc that all these registers could change,
 		      * which means we don't have to save and restore them in
 		      * the Switcher. */
@@ -223,7 +223,7 @@ static int emulate_insn(struct lg_cpu *cpu)
 	unsigned int insnlen = 0, in = 0, shift = 0;
 	/* The eip contains the *virtual* address of the Guest's instruction:
 	 * guest_pa just subtracts the Guest's page_offset. */
-	unsigned long physaddr = guest_pa(lg, cpu->regs->eip);
+	unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
 
 	/* This must be the Guest kernel trying to do something, not userspace!
 	 * The bottom two bits of the CS segment register are the privilege
@@ -305,7 +305,8 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
 		 *
 		 * The errcode tells whether this was a read or a write, and
 		 * whether kernel or userspace code. */
-		if (demand_page(lg,cpu->arch.last_pagefault,cpu->regs->errcode))
+		if (demand_page(cpu, cpu->arch.last_pagefault,
+				cpu->regs->errcode))
 			return;
 
 		/* OK, it's really not there (or not OK): the Guest needs to