On April 26, 2023 5:08:57 PM PDT, Anthony Yznaga <anthony.yznaga@xxxxxxxxxx> wrote: >pkram kaslr code can incur multiple page faults when it walks its >preserved ranges list called via mem_avoid_overlap(). The multiple >faults can easily end up using up the small number of pages available >to be allocated for page table pages. > >This patch hacks things so that mappings are 1GB which results in the need >for far fewer page table pages. As is this breaks AMD SEV-ES which expects >the mappings to be 2M. This could possibly be fixed by updating split >code to split 1GB page if the aren't any other issues with using 1GB >mappings. > >Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx> >--- > arch/x86/boot/compressed/ident_map_64.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > >diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c >index 321a5011042d..1e02cf6dda3c 100644 >--- a/arch/x86/boot/compressed/ident_map_64.c >+++ b/arch/x86/boot/compressed/ident_map_64.c >@@ -95,8 +95,8 @@ void kernel_add_identity_map(unsigned long start, unsigned long end) > int ret; > > /* Align boundary to 2M. */ >- start = round_down(start, PMD_SIZE); >- end = round_up(end, PMD_SIZE); >+ start = round_down(start, PUD_SIZE); >+ end = round_up(end, PUD_SIZE); > if (start >= end) > return; > >@@ -120,6 +120,7 @@ void initialize_identity_maps(void *rmode) > mapping_info.context = &pgt_data; > mapping_info.page_flag = __PAGE_KERNEL_LARGE_EXEC | sme_me_mask; > mapping_info.kernpg_flag = _KERNPG_TABLE; >+ mapping_info.direct_gbpages = true; > > /* > * It should be impossible for this not to already be true, >@@ -365,8 +366,8 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code) > > ghcb_fault = sev_es_check_ghcb_fault(address); > >- address &= PMD_MASK; >- end = address + PMD_SIZE; >+ address &= PUD_MASK; >+ end = address + PUD_SIZE; > > /* > * Check for unexpected error codes. Unexpected are: Strong NAK: 1G pages are not supported by all 64-bit CPUs, *and* by your own admission breaks things ...
