Re: [PATCH] x86/head/64: level2_kernel_pgt's kernel area is built with _PAGE_PRESENT set

Wei Yang
2024-05-22T07:34:52Z

On Sat, Mar 23, 2024 at 11:26:21PM +0000, Wei Yang wrote:
>The code is first introduced in 'commit 1ab60e0f72f7 ("[PATCH] x86-64:
>Relocatable Kernel Support")'. Then 'commit c88d71508e36b
>("x86/boot/64: Rewrite startup_64() in C")', convert it to c. And
>'commit 2aa85f246c181 ("x86/boot/64: Make level2_kernel_pgt pages
>invalid outside kernel area")' limit the range from _text to _end.
>
>Originally, it does the check because the loop iterate the whole
>level2_kernel_pgt, while currently it just fixup the kernel area. This
>area is built with _PAGE_PRESENT set.

Ping

>
>Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>CC: Vivek Goyal <vgoyal@in.ibm.com>
>CC: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>CC: Ingo Molnar <mingo@kernel.org>
>CC: Steve Wahl <steve.wahl@hpe.com>
>CC: Borislav Petkov <bp@suse.de>
>---
> arch/x86/kernel/head64.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
>diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
>index 212e8e06aeba..75c69f8620d8 100644
>--- a/arch/x86/kernel/head64.c
>+++ b/arch/x86/kernel/head64.c
>@@ -253,8 +253,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
>
> /* fixup pages that are part of the kernel image */
> for (; i <= pmd_index((unsigned long)_end); i++)
>- if (pmd[i] & _PAGE_PRESENT)
>- pmd[i] += load_delta;
>+ pmd[i] += load_delta;
>
> /* invalidate pages after the kernel image */
> for (; i < PTRS_PER_PMD; i++)
>--
>2.34.1