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Commit 7313d521 authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: add iomem region, where guest page faults get sent to userspace. 



This lets us implement PCI.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent d1c29465

drivers/lguest/lg.h

+6 −1
Original line number Diff line number Diff line
@@ -97,8 +97,12 @@ struct lguest { 
	struct lg_cpu cpus[NR_CPUS];

	unsigned int nr_cpus;



	/* Valid guest memory pages must be < this. */

	u32 pfn_limit;



	/* Device memory is >= pfn_limit and < device_limit. */

	u32 device_limit;



	/*

	 * This provides the offset to the base of guest-physical memory in the

	 * Launcher.
@@ -200,7 +204,8 @@ void guest_pagetable_flush_user(struct lg_cpu *cpu); 
void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir,

		   unsigned long vaddr, pte_t val);

void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);

bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);

bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode,

		 unsigned long *iomem);

void pin_page(struct lg_cpu *cpu, unsigned long vaddr);

bool __guest_pa(struct lg_cpu *cpu, unsigned long vaddr, unsigned long *paddr);

unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr);

drivers/lguest/lguest_user.c

+2 −1
Original line number Diff line number Diff line
@@ -385,7 +385,7 @@ static int initialize(struct file *file, const unsigned long __user *input) 
	/* "struct lguest" contains all we (the Host) know about a Guest. */

	struct lguest *lg;

	int err;

	unsigned long args[3];

	unsigned long args[4];



	/*

	 * We grab the Big Lguest lock, which protects against multiple
@@ -419,6 +419,7 @@ static int initialize(struct file *file, const unsigned long __user *input) 
	/* Populate the easy fields of our "struct lguest" */

	lg->mem_base = (void __user *)args[0];

	lg->pfn_limit = args[1];

	lg->device_limit = args[3];



	/* This is the first cpu (cpu 0) and it will start booting at args[2] */

	err = lg_cpu_start(&lg->cpus[0], 0, args[2]);

drivers/lguest/page_tables.c

+30 −3
Original line number Diff line number Diff line
@@ -250,6 +250,16 @@ static void release_pte(pte_t pte) 
}

/*:*/



static bool gpte_in_iomem(struct lg_cpu *cpu, pte_t gpte)

{

	/* We don't handle large pages. */

	if (pte_flags(gpte) & _PAGE_PSE)

		return false;



	return (pte_pfn(gpte) >= cpu->lg->pfn_limit

		&& pte_pfn(gpte) < cpu->lg->device_limit);

}



static bool check_gpte(struct lg_cpu *cpu, pte_t gpte)

{

	if ((pte_flags(gpte) & _PAGE_PSE) ||
@@ -374,8 +384,14 @@ static pte_t *find_spte(struct lg_cpu *cpu, unsigned long vaddr, bool allocate, 
 *

 * 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.

 *

 * There's a corner case: they're trying to access memory between

 * pfn_limit and device_limit, which is I/O memory.  In this case, we

 * return false and set @iomem to the physical address, so the the

 * Launcher can handle the instruction manually.

 */

bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)

bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode,

		 unsigned long *iomem)

{

	unsigned long gpte_ptr;

	pte_t gpte;
@@ -383,6 +399,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) 
	pmd_t gpmd;

	pgd_t gpgd;



	*iomem = 0;



	/* We never demand page the Switcher, so trying is a mistake. */

	if (vaddr >= switcher_addr)

		return false;
@@ -459,6 +477,12 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) 
	if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))

		return false;



	/* If they're accessing io memory, we expect a fault. */

	if (gpte_in_iomem(cpu, gpte)) {

		*iomem = (pte_pfn(gpte) << PAGE_SHIFT) | (vaddr & ~PAGE_MASK);

		return false;

	}



	/*

	 * Check that the Guest PTE flags are OK, and the page number is below

	 * the pfn_limit (ie. not mapping the Launcher binary).
@@ -553,7 +577,9 @@ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) 
 */

void pin_page(struct lg_cpu *cpu, unsigned long vaddr)

{

	if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))

	unsigned long iomem;



	if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2, &iomem))

		kill_guest(cpu, "bad stack page %#lx", vaddr);

}

/*:*/
@@ -928,7 +954,8 @@ static void __guest_set_pte(struct lg_cpu *cpu, int idx, 
			 * now.  This shaves 10% off a copy-on-write

			 * micro-benchmark.

			 */

			if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {

			if ((pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED))

			    && !gpte_in_iomem(cpu, gpte)) {

				if (!check_gpte(cpu, gpte))

					return;

				set_pte(spte,

drivers/lguest/x86/core.c

+18 −1
Original line number Diff line number Diff line
@@ -362,9 +362,19 @@ static void setup_emulate_insn(struct lg_cpu *cpu) 
			sizeof(cpu->pending.insn));

}



static void setup_iomem_insn(struct lg_cpu *cpu, unsigned long iomem_addr)

{

	cpu->pending.trap = 14;

	cpu->pending.addr = iomem_addr;

	copy_from_guest(cpu, cpu->pending.insn, cpu->regs->eip,

			sizeof(cpu->pending.insn));

}



/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */

void lguest_arch_handle_trap(struct lg_cpu *cpu)

{

	unsigned long iomem_addr;



	switch (cpu->regs->trapnum) {

	case 13: /* We've intercepted a General Protection Fault. */

		/* Hand to Launcher to emulate those pesky IN and OUT insns */
@@ -385,8 +395,15 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) 
		 * whether kernel or userspace code.

		 */

		if (demand_page(cpu, cpu->arch.last_pagefault,

				cpu->regs->errcode))

				cpu->regs->errcode, &iomem_addr))

			return;



		/* Was this an access to memory mapped IO? */

		if (iomem_addr) {

			/* Tell Launcher, let it handle it. */

			setup_iomem_insn(cpu, iomem_addr);

			return;

		}



		/*

		 * OK, it's really not there (or not OK): the Guest needs to

tools/lguest/lguest.c

+2 −1
Original line number Diff line number Diff line
@@ -548,7 +548,8 @@ static void tell_kernel(unsigned long start) 
{

	unsigned long args[] = { LHREQ_INITIALIZE,

				 (unsigned long)guest_base,

				 guest_limit / getpagesize(), start };

				 guest_limit / getpagesize(), start,

				 guest_limit / getpagesize() };

	verbose("Guest: %p - %p (%#lx)\n",

		guest_base, guest_base + guest_limit, guest_limit);

	lguest_fd = open_or_die("/dev/lguest", O_RDWR);