linux-kernel - Re: [PATCH] x86/head/64: level2_kernel_pgt's kernel area is built with _PAGE

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Message-ID: <20240522073449.sd4qfvysvjbkc6t3@master>
Date: Wed, 22 May 2024 07:34:49 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Wei Yang <richard.weiyang@...il.com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, Vivek Goyal <vgoyal@...ibm.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Steve Wahl <steve.wahl@....com>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] x86/head/64: level2_kernel_pgt's kernel area is built
 with _PAGE_PRESENT set

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@...il.com>
>CC: Vivek Goyal <vgoyal@...ibm.com>
>CC: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
>CC: Ingo Molnar <mingo@...nel.org>
>CC: Steve Wahl <steve.wahl@....com>
>CC: Borislav Petkov <bp@...e.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

-- 
Wei Yang
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