Signed-off-by: Rusty Russell --- arch/x86/lguest/boot.c | 4 ++-- drivers/lguest/page_tables.c | 9 +++++---- 2 files changed, 7 insertions(+), 6 deletions(-) diff -r c0506c353a7c arch/x86/lguest/boot.c --- a/arch/x86/lguest/boot.c Tue Aug 19 19:36:56 2008 +1000 +++ b/arch/x86/lguest/boot.c Mon Aug 25 09:50:02 2008 +1000 @@ -340,8 +340,8 @@ static void lguest_cpuid(unsigned int *a * kernel mappings (addresses above 0xC0000000 or whatever * PAGE_OFFSET is set to) haven't changed. But Linux calls * flush_tlb_user() for both user and kernel mappings unless - * the Page Global Enable (PGE) feature bit is set. */ - /* Lets also try with PSE support */ + * the Page Global Enable (PGE) feature bit is set. We also + * turn on Page Size Extention (PSE) which allows 4MB pages. */ *dx |= 0x00002008; break; case 0x80000000: diff -r c0506c353a7c drivers/lguest/page_tables.c --- a/drivers/lguest/page_tables.c Tue Aug 19 19:36:56 2008 +1000 +++ b/drivers/lguest/page_tables.c Mon Aug 25 09:50:02 2008 +1000 @@ -219,9 +219,10 @@ int demand_page(struct lg_cpu *cpu, unsi if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) return 0; - /* If the gpgd is actually pointing to a 4MB page, - * instead of pointing to a pte page, we will back it - * with 4KB pages in the host */ + /* The Guest can set the PSE bit which means instead of pointing to a + * page of page table entries, this itself is a page table entry to a + * 4MB page. But it's hard for us to get a 4MB page to use here in the + * Host, so the shadow doesn't use PTE: we make a normal page table. */ if (pgd_flags(gpgd) & _PAGE_PSE) { /* Check they're not trying to write to a page the Guest wants * read-only (bit 2 of errcode == write). */ @@ -248,7 +249,7 @@ int demand_page(struct lg_cpu *cpu, unsi "out of memory allocating pte page"); /* We build a shadow pgd, pointing to the PTE page */ set_pgd(spgd, __pgd(__pa(ptepage) | - (pgd_flags(gpgd) & ~_PAGE_PSE & _PAGE_TABLE))); + (pgd_flags(gpgd) & ~_PAGE_PSE & _PAGE_TABLE))); } /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */