Hi Greg,
On Sat, Sep 29, 2018 at 04:40:02PM -0700, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.9-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Thanks for the note. I will take a look at this, and it may take a while
as we are on Chinese National Holidays.
Thanks,
Feng
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> >From 05ab1d8a4b36ee912b7087c6da127439ed0a903e Mon Sep 17 00:00:00 2001
> From: Feng Tang <feng.tang@xxxxxxxxx>
> Date: Thu, 20 Sep 2018 10:58:28 +0800
> Subject: [PATCH] x86/mm: Expand static page table for fixmap space
>
> We met a kernel panic when enabling earlycon, which is due to the fixmap
> address of earlycon is not statically setup.
>
> Currently the static fixmap setup in head_64.S only covers 2M virtual
> address space, while it actually could be in 4M space with different
> kernel configurations, e.g. when VSYSCALL emulation is disabled.
>
> So increase the static space to 4M for now by defining FIXMAP_PMD_NUM to 2,
> and add a build time check to ensure that the fixmap is covered by the
> initial static page tables.
>
> Fixes: 1ad83c858c7d ("x86_64,vsyscall: Make vsyscall emulation configurable")
> Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Tested-by: kernel test robot <rong.a.chen@xxxxxxxxx>
> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> (Xen parts)
> Cc: H Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Cc: Andy Lutomirsky <luto@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://lkml.kernel.org/r/20180920025828.23699-1-feng.tang@xxxxxxxxx
>
> diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
> index e203169931c7..6390bd8c141b 100644
> --- a/arch/x86/include/asm/fixmap.h
> +++ b/arch/x86/include/asm/fixmap.h
> @@ -14,6 +14,16 @@
> #ifndef _ASM_X86_FIXMAP_H
> #define _ASM_X86_FIXMAP_H
>
> +/*
> + * Exposed to assembly code for setting up initial page tables. Cannot be
> + * calculated in assembly code (fixmap entries are an enum), but is sanity
> + * checked in the actual fixmap C code to make sure that the fixmap is
> + * covered fully.
> + */
> +#define FIXMAP_PMD_NUM 2
> +/* fixmap starts downwards from the 507th entry in level2_fixmap_pgt */
> +#define FIXMAP_PMD_TOP 507
> +
> #ifndef __ASSEMBLY__
> #include <linux/kernel.h>
> #include <asm/acpi.h>
> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
> index ce2b59047cb8..9c85b54bf03c 100644
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -14,6 +14,7 @@
> #include <asm/processor.h>
> #include <linux/bitops.h>
> #include <linux/threads.h>
> +#include <asm/fixmap.h>
>
> extern p4d_t level4_kernel_pgt[512];
> extern p4d_t level4_ident_pgt[512];
> @@ -22,7 +23,7 @@ extern pud_t level3_ident_pgt[512];
> extern pmd_t level2_kernel_pgt[512];
> extern pmd_t level2_fixmap_pgt[512];
> extern pmd_t level2_ident_pgt[512];
> -extern pte_t level1_fixmap_pgt[512];
> +extern pte_t level1_fixmap_pgt[512 * FIXMAP_PMD_NUM];
> extern pgd_t init_top_pgt[];
>
> #define swapper_pg_dir init_top_pgt
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index c16af27eb23f..ddee1f0870c4 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -35,6 +35,7 @@
> #include <asm/bootparam_utils.h>
> #include <asm/microcode.h>
> #include <asm/kasan.h>
> +#include <asm/fixmap.h>
>
> /*
> * Manage page tables very early on.
> @@ -166,7 +167,8 @@ unsigned long __head __startup_64(unsigned long physaddr,
> pud[511] += load_delta;
>
> pmd = fixup_pointer(level2_fixmap_pgt, physaddr);
> - pmd[506] += load_delta;
> + for (i = FIXMAP_PMD_TOP; i > FIXMAP_PMD_TOP - FIXMAP_PMD_NUM; i--)
> + pmd[i] += load_delta;
>
> /*
> * Set up the identity mapping for the switchover. These
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 15ebc2fc166e..a3618cf04cf6 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -24,6 +24,7 @@
> #include "../entry/calling.h"
> #include <asm/export.h>
> #include <asm/nospec-branch.h>
> +#include <asm/fixmap.h>
>
> #ifdef CONFIG_PARAVIRT
> #include <asm/asm-offsets.h>
> @@ -445,13 +446,20 @@ NEXT_PAGE(level2_kernel_pgt)
> KERNEL_IMAGE_SIZE/PMD_SIZE)
>
> NEXT_PAGE(level2_fixmap_pgt)
> - .fill 506,8,0
> - .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
> - /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
> - .fill 5,8,0
> + .fill (512 - 4 - FIXMAP_PMD_NUM),8,0
> + pgtno = 0
> + .rept (FIXMAP_PMD_NUM)
> + .quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
> + + _PAGE_TABLE_NOENC;
> + pgtno = pgtno + 1
> + .endr
> + /* 6 MB reserved space + a 2MB hole */
> + .fill 4,8,0
>
> NEXT_PAGE(level1_fixmap_pgt)
> + .rept (FIXMAP_PMD_NUM)
> .fill 512,8,0
> + .endr
>
> #undef PMDS
>
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index ae394552fb94..089e78c4effd 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -637,6 +637,15 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
> {
> unsigned long address = __fix_to_virt(idx);
>
> +#ifdef CONFIG_X86_64
> + /*
> + * Ensure that the static initial page tables are covering the
> + * fixmap completely.
> + */
> + BUILD_BUG_ON(__end_of_permanent_fixed_addresses >
> + (FIXMAP_PMD_NUM * PTRS_PER_PTE));
> +#endif
> +
> if (idx >= __end_of_fixed_addresses) {
> BUG();
> return;
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 2fe5c9b1816b..dd461c0167ef 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -1907,7 +1907,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
> /* L3_k[511] -> level2_fixmap_pgt */
> convert_pfn_mfn(level3_kernel_pgt);
>
> - /* L3_k[511][506] -> level1_fixmap_pgt */
> + /* L3_k[511][508-FIXMAP_PMD_NUM ... 507] -> level1_fixmap_pgt */
> convert_pfn_mfn(level2_fixmap_pgt);
>
> /* We get [511][511] and have Xen's version of level2_kernel_pgt */
> @@ -1952,7 +1952,11 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
> set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
> set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
> set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
> - set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO);
> +
> + for (i = 0; i < FIXMAP_PMD_NUM; i++) {
> + set_page_prot(level1_fixmap_pgt + i * PTRS_PER_PTE,
> + PAGE_KERNEL_RO);
> + }
>
> /* Pin down new L4 */
> pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
