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authorRusty Russell <rusty@rustcorp.com.au>2015-02-11 15:15:10 +1030
committerRusty Russell <rusty@rustcorp.com.au>2015-02-11 16:47:33 +1030
commit7313d5217e6b9817897172d6a6ff477bdc415ed6 (patch)
tree448fc79d9048af296aeb6c6fbbf5da84dc6f7046 /drivers/lguest/page_tables.c
parentd1c29465b8a52d8fc5a59aac92c6b206b69fe631 (diff)
downloadlinux-7313d5217e6b9817897172d6a6ff477bdc415ed6.tar.bz2
lguest: add iomem region, where guest page faults get sent to userspace.
This lets us implement PCI. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/lguest/page_tables.c')
-rw-r--r--drivers/lguest/page_tables.c33
1 files changed, 30 insertions, 3 deletions
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 69c35caa955a..e3abebc912c0 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -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,