lguest: fix early_ioremap.
dmi_scan_machine breaks under lguest:
lguest: unhandled trap 14 at 0xc04edeae (0xffa00000)
This is because we use current_cr3 for the read_cr3() paravirt
function, and it isn't set until the first cr3 change. We got away
with it until this happened.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 48ee4f9..4e22fa0 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -367,10 +367,9 @@
* lazily after a task switch, and Linux uses that gratefully, but wouldn't a
* name like "FPUTRAP bit" be a little less cryptic?
*
- * We store cr0 (and cr3) locally, because the Host never changes it. The
- * Guest sometimes wants to read it and we'd prefer not to bother the Host
- * unnecessarily. */
-static unsigned long current_cr0, current_cr3;
+ * We store cr0 locally because the Host never changes it. The Guest sometimes
+ * wants to read it and we'd prefer not to bother the Host unnecessarily. */
+static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
lazy_hcall(LHCALL_TS, val & X86_CR0_TS, 0, 0);
@@ -399,17 +398,23 @@
return lguest_data.cr2;
}
+/* See lguest_set_pte() below. */
+static bool cr3_changed = false;
+
/* cr3 is the current toplevel pagetable page: the principle is the same as
- * cr0. Keep a local copy, and tell the Host when it changes. */
+ * cr0. Keep a local copy, and tell the Host when it changes. The only
+ * difference is that our local copy is in lguest_data because the Host needs
+ * to set it upon our initial hypercall. */
static void lguest_write_cr3(unsigned long cr3)
{
+ lguest_data.pgdir = cr3;
lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0);
- current_cr3 = cr3;
+ cr3_changed = true;
}
static unsigned long lguest_read_cr3(void)
{
- return current_cr3;
+ return lguest_data.pgdir;
}
/* cr4 is used to enable and disable PGE, but we don't care. */
@@ -498,13 +503,13 @@
* to forget all of them. Fortunately, this is very rare.
*
* ... except in early boot when the kernel sets up the initial pagetables,
- * which makes booting astonishingly slow. So we don't even tell the Host
- * anything changed until we've done the first page table switch. */
+ * which makes booting astonishingly slow: 1.83 seconds! So we don't even tell
+ * the Host anything changed until we've done the first page table switch,
+ * which brings boot back to 0.25 seconds. */
static void lguest_set_pte(pte_t *ptep, pte_t pteval)
{
*ptep = pteval;
- /* Don't bother with hypercall before initial setup. */
- if (current_cr3)
+ if (cr3_changed)
lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
}
@@ -521,7 +526,7 @@
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
- lazy_hcall(LHCALL_SET_PTE, current_cr3, addr, 0);
+ lazy_hcall(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
}
/* This is what happens after the Guest has removed a large number of entries.