lguest: map Switcher below fixmap.
Now we've adjusted all the code, we can simply set switcher_addr to
wherever it needs to go below the fixmaps, rather than asserting that
it should be so.
With large NR_CPUS and PAE, people were hitting the "mapping switcher
would thwack fixmap" message.
Reported-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/arch/x86/include/asm/lguest.h b/arch/x86/include/asm/lguest.h
index 74edebd..e2d4a4a 100644
--- a/arch/x86/include/asm/lguest.h
+++ b/arch/x86/include/asm/lguest.h
@@ -14,12 +14,6 @@
/* Page for Switcher text itself, then two pages per cpu */
#define TOTAL_SWITCHER_PAGES (1 + 2 * nr_cpu_ids)
-/* We map at -4M (-2M for PAE) for ease of mapping (one PTE page). */
-#ifdef CONFIG_X86_PAE
-#define SWITCHER_ADDR 0xFFE00000
-#else
-#define SWITCHER_ADDR 0xFFC00000
-#endif
/* Where we map the Switcher, in both Host and Guest. */
extern unsigned long switcher_addr;
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 7e1d7ee..0bf1e4e 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -83,18 +83,13 @@
}
}
- switcher_addr = SWITCHER_ADDR;
-
/*
- * First we check that the Switcher won't overlap the fixmap area at
- * the top of memory. It's currently nowhere near, but it could have
- * very strange effects if it ever happened.
+ * We place the Switcher underneath the fixmap area, which is the
+ * highest virtual address we can get. This is important, since we
+ * tell the Guest it can't access this memory, so we want its ceiling
+ * as high as possible.
*/
- if (switcher_addr + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
- err = -ENOMEM;
- printk("lguest: mapping switcher would thwack fixmap\n");
- goto free_pages;
- }
+ switcher_addr = FIXADDR_START - (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE;
/*
* Now we reserve the "virtual memory area" we want. We might