This patch preallocates the intermediate page table entries so that all that is needed to setup a fixmap is to fill in the appropriate pte. By doing this modern hardware that uses memory mapped access can be talked to early in boot through a fixmap. Allowing USB debugging and the like. Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> --- arch/x86_64/kernel/head.S | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-) diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S index 1fab487..1b704c4 100644 --- a/arch/x86_64/kernel/head.S +++ b/arch/x86_64/kernel/head.S @@ -74,6 +74,9 @@ startup_64: addq %rbp, level3_ident_pgt + 0(%rip) addq %rbp, level3_kernel_pgt + (510*8)(%rip) + addq %rbp, level3_kernel_pgt + (511*8)(%rip) + + addq %rbp, level2_fixmap_pgt + (506*8)(%rip) /* Add an Identity mapping if I am above 1G */ leaq _text(%rip), %rdi @@ -314,7 +317,16 @@ NEXT_PAGE(level3_kernel_pgt) .fill 510,8,0 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */ .quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE - .fill 1,8,0 + .quad level2_fixmap_pgt - __START_KERNEL_map + _KERNPG_TABLE + _PAGE_USER + +NEXT_PAGE(level2_fixmap_pgt) + .fill 506,8,0 + .quad level1_fixmap_pgt - __START_KERNEL_map + _KERNPG_TABLE + _PAGE_USER + /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ + .fill 5,8,0 + +NEXT_PAGE(level1_fixmap_pgt) + .fill 512,8,0 NEXT_PAGE(level2_ident_pgt) /* Since I easily can, map the first 1G. -- 1.5.1.1.181.g2de0 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
