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Fix for page faults under KVM

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Under KVM we were hitting what look like out-of-order and/or issues
during initialization when writing to the page tables and then
immediately writing to the mapped memory.  Adding a memory barrier and
an io_wait() in memory_bootstrap.cpp fixed it.
This commit is contained in:
Justin C. Miller
2018-09-21 20:32:28 -07:00
parent f1bb3556eb
commit d8399e3c07
1 changed files with 6 additions and 2 deletions
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8
src/kernel/memory_bootstrap.cpp
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@@ -2,7 +2,7 @@
#include "kutil/assert.h" #include "kutil/assert.h"
#include "kutil/linked_list.h" #include "kutil/linked_list.h"
#include "kutil/slab_allocator.h" #include "kutil/slab_allocator.h"
#include "memory.h" #include "io.h"
#include "page_manager.h" #include "page_manager.h"
const unsigned efi_page_size = 0x1000; const unsigned efi_page_size = 0x1000;
@@ -402,7 +402,7 @@ memory_initialize(const void *memory_map, size_t map_length, size_t desc_length)
uint64_t free_next = free_region_start_virt; uint64_t free_next = free_region_start_virt;
// We'll need to copy any existing tables (except the PML4 which the // We'll need to copy any existing tables (except the PML4 which the
// bootloader gave us) into our 4 reserved pages so we can edit them. // bootloader gave us) into our reserved pages so we can edit them.
page_table_indices fr_idx{free_region_start_virt}; page_table_indices fr_idx{free_region_start_virt};
copy_new_table(&tables[0], fr_idx[0], &tables[1]); copy_new_table(&tables[0], fr_idx[0], &tables[1]);
@@ -473,6 +473,10 @@ memory_initialize(const void *memory_map, size_t map_length, size_t desc_length)
page_in_ident(&tables[0], pt_start_phys, pt_start_virt, remaining_pages, tables + 4); page_in_ident(&tables[0], pt_start_phys, pt_start_virt, remaining_pages, tables + 4);
// Make sure the page table is finished updating before we write to memory
__sync_synchronize();
io_wait();
// Finally, build an acutal set of kernel page tables that just contains // Finally, build an acutal set of kernel page tables that just contains
// what the kernel actually has mapped, but making everything writable // what the kernel actually has mapped, but making everything writable
// (especially the page tables themselves) // (especially the page tables themselves)