linux-kernel - [RFC PATCH v4 07/20] x86/kexec: Copy control page into place in machine_kexec

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Message-ID: <20241127190343.44916-8-dwmw2@infradead.org>
Date: Wed, 27 Nov 2024 19:00:21 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: kexec@...ts.infradead.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	linux-kernel@...r.kernel.org,
	Simon Horman <horms@...nel.org>,
	Dave Young <dyoung@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	jpoimboe@...nel.org,
	bsz@...zon.de
Subject: [RFC PATCH v4 07/20] x86/kexec: Copy control page into place in machine_kexec_prepare()

From: David Woodhouse <dwmw@...zon.co.uk>

There's no need for this to wait until the actual machine_kexec() invocation;
future changes will need to make the control page read-only and executable,
so all writes should be completed before machine_kexec_prepare() returns.

Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 arch/x86/kernel/machine_kexec_64.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 7223c38a8708..3a4cbac1a0c6 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -301,17 +301,16 @@ static void load_segments(void)
 
 int machine_kexec_prepare(struct kimage *image)
 {
-	unsigned long control_page;
+	void *control_page = page_address(image->control_code_page);
 	int result;
 
-	/* Calculate the offsets */
-	control_page = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
-
 	/* Setup the identity mapped 64bit page table */
-	result = init_pgtable(image, control_page);
+	result = init_pgtable(image, __pa(control_page));
 	if (result)
 		return result;
 
+	__memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
+
 	return 0;
 }
 
@@ -363,7 +362,6 @@ void machine_kexec(struct kimage *image)
 	}
 
 	control_page = page_address(image->control_code_page);
-	__memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
 
 	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
 	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
-- 
2.47.0