Debugged why guest was crashing immediately with unhandled page fault, also
fixed a potential future problem. Please review.
lguest: PAE fixes
1) j wasn't initialized in setup_pagetables, so they weren't set up for me
causing immediate guest crashes.
2) gpte_addr should not re-read the pmd from the Guest. Especially
not BUG_ON() based on the value. If we ever supported SMP guests,
they could trigger that. And the Launcher could also trigger it
(tho currently root-only).
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -154,26 +154,25 @@ static unsigned long gpmd_addr(pgd_t gpg
BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT));
return gpage + pmd_index(vaddr) * sizeof(pmd_t);
}
-#endif
static unsigned long gpte_addr(struct lg_cpu *cpu,
+ pmd_t gpmd, unsigned long vaddr)
+{
+ unsigned long gpage = pmd_pfn(gpmd) << PAGE_SHIFT;
+
+ BUG_ON(!(pmd_flags(gpmd) & _PAGE_PRESENT));
+ return gpage + pte_index(vaddr) * sizeof(pte_t);
+}
+#else
+static unsigned long gpte_addr(struct lg_cpu *cpu,
pgd_t gpgd, unsigned long vaddr)
{
-#ifdef CONFIG_X86_PAE
- pmd_t gpmd;
-#endif
- unsigned long gpage;
+ unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT;
BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT));
-#ifdef CONFIG_X86_PAE
- gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
- gpage = pmd_pfn(gpmd) << PAGE_SHIFT;
- BUG_ON(!(pmd_flags(gpmd) & _PAGE_PRESENT));
-#else
- gpage = pgd_pfn(gpgd) << PAGE_SHIFT;
-#endif
return gpage + pte_index(vaddr) * sizeof(pte_t);
}
+#endif
/*:*/
/*M:014 get_pfn is slow: we could probably try to grab batches of pages here as
@@ -339,10 +338,15 @@ bool demand_page(struct lg_cpu *cpu, uns
* number in the shadow PMD is the page we just allocated. */
native_set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd)));
}
-#endif
+
+ /* OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later. */
+ gpte_ptr = gpte_addr(cpu, gpmd, vaddr);
+#else
/* OK, now we look at the lower level in the Guest page table: keep its
* address, because we might update it later. */
gpte_ptr = gpte_addr(cpu, gpgd, vaddr);
+#endif
gpte = lgread(cpu, gpte_ptr, pte_t);
/* If this page isn't in the Guest page tables, we can't page it in. */
@@ -522,7 +526,6 @@ unsigned long guest_pa(struct lg_cpu *cp
{
pgd_t gpgd;
pte_t gpte;
-
#ifdef CONFIG_X86_PAE
pmd_t gpmd;
#endif
@@ -534,13 +537,14 @@ unsigned long guest_pa(struct lg_cpu *cp
return -1UL;
}
- gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);
#ifdef CONFIG_X86_PAE
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
kill_guest(cpu, "Bad address %#lx", vaddr);
+ gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t);
+#else
+ gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);
#endif
- gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);
if (!(pte_flags(gpte) & _PAGE_PRESENT))
kill_guest(cpu, "Bad address %#lx", vaddr);
@@ -847,7 +851,7 @@ static unsigned long setup_pagetables(st
/* The top level points to the linear page table pages above.
* We setup the identity and linear mappings here. */
#ifdef CONFIG_X86_PAE
- for (i = 0, j; i < mapped_pages && j < PTRS_PER_PMD;
+ for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD;
i += PTRS_PER_PTE, j++) {
native_set_pmd(&pmd, __pmd(((unsigned long)(linear + i)
- mem_base) | _PAGE_PRESENT | _PAGE_RW | _PAGE_USER));
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