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Commit ad5173ff authored by Rusty Russell's avatar Rusty Russell
Browse files

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: default avatarRusty Russell <rusty@rustcorp.com.au>
parent d5d02d6d

arch/x86/lguest/boot.c

+17 −12
Original line number Diff line number Diff line
@@ -367,10 +367,9 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx, 
 * 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 @@ static unsigned long lguest_read_cr2(void) 
	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 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval) 
 * 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_set_pte(pte_t *ptep, pte_t pteval) 
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.