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| author | Rusty Russell <rusty@rustcorp.com.au> | 2011-07-22 14:39:48 +0930 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2011-07-22 14:39:48 +0930 |
| commit | 5dea1c88ed11a1221581c4b202f053c4fc138704 (patch) | |
| tree | 59e15d3c696712e26ffb229ff987f33bcc72affe /arch/x86/lguest | |
| parent | e0377e25206328998d036cafddcd00a7c3252e3e (diff) | |
| download | linux-5dea1c88ed11a1221581c4b202f053c4fc138704.tar.bz2 | |
lguest: use a special 1:1 linear pagetable mode until first switch.
The Host used to create some page tables for the Guest to use at the
top of Guest memory; it would then tell the Guest where this was. In
particular, it created linear mappings for 0 and 0xC0000000 addresses
because lguest used to switch to its real page tables quite late in
boot.
However, since d50d8fe19 Linux initialized boot page tables in
head_32.S even before the "are we lguest?" boot jump. So, now we can
simplify things: the Host pagetable code assumes 1:1 linear mapping
until it first calls the LHCALL_NEW_PGTABLE hypercall, which we now do
before we reach C code.
This also means that the Host doesn't need to know anything about the
Guest's PAGE_OFFSET. (Non-Linux guests might not even have such a
thing).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'arch/x86/lguest')
| -rw-r--r-- | arch/x86/lguest/boot.c | 11 | ||||
| -rw-r--r-- | arch/x86/lguest/i386_head.S | 9 |
2 files changed, 12 insertions, 8 deletions
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index db832fd65ecb..719a32c60516 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -520,17 +520,16 @@ static unsigned long lguest_read_cr2(void) /* See lguest_set_pte() below. */ static bool cr3_changed = false; +static unsigned long current_cr3; /* * 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. The only - * difference is that our local copy is in lguest_data because the Host needs - * to set it upon our initial hypercall. + * cr0. Keep a local copy, and tell the Host when it changes. */ static void lguest_write_cr3(unsigned long cr3) { - lguest_data.pgdir = cr3; lazy_hcall1(LHCALL_NEW_PGTABLE, cr3); + current_cr3 = cr3; /* These two page tables are simple, linear, and used during boot */ if (cr3 != __pa(swapper_pg_dir) && cr3 != __pa(initial_page_table)) @@ -539,7 +538,7 @@ static void lguest_write_cr3(unsigned long cr3) static unsigned long lguest_read_cr3(void) { - return lguest_data.pgdir; + return current_cr3; } /* cr4 is used to enable and disable PGE, but we don't care. */ @@ -758,7 +757,7 @@ static void lguest_pmd_clear(pmd_t *pmdp) static void lguest_flush_tlb_single(unsigned long addr) { /* Simply set it to zero: if it was not, it will fault back in. */ - lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0); + lazy_hcall3(LHCALL_SET_PTE, current_cr3, addr, 0); } /* diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S index 4f420c2f2d55..863b03a9fbff 100644 --- a/arch/x86/lguest/i386_head.S +++ b/arch/x86/lguest/i386_head.S @@ -27,13 +27,18 @@ .section .init.text, "ax", @progbits ENTRY(lguest_entry) /* - * We make the "initialization" hypercall now to tell the Host about - * us, and also find out where it put our page tables. + * We make the "initialization" hypercall now to tell the Host where + * our lguest_data struct is. */ movl $LHCALL_LGUEST_INIT, %eax movl $lguest_data - __PAGE_OFFSET, %ebx int $LGUEST_TRAP_ENTRY + /* Now turn our pagetables on; setup by arch/x86/kernel/head_32.S. */ + movl $LHCALL_NEW_PGTABLE, %eax + movl $(initial_page_table - __PAGE_OFFSET), %ebx + int $LGUEST_TRAP_ENTRY + /* Set up the initial stack so we can run C code. */ movl $(init_thread_union+THREAD_SIZE),%esp |