linux-kernel - [RFC PATCH v2 08/16] x86/kexec: Copy control page into place in machine_kexec

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Message-ID: <20241122224715.171751-9-dwmw2@infradead.org>
Date: Fri, 22 Nov 2024 22:38:17 +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
Subject: [RFC PATCH v2 08/16] 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;
a subsequent change will mark the control page ROX so all writes should be
completed earlier.

Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 arch/x86/kernel/machine_kexec_64.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 123e9544506b..60632a5a2a13 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -297,6 +297,8 @@ static void load_segments(void)
 int machine_kexec_prepare(struct kimage *image)
 {
 	void *control_page = page_address(image->control_code_page) + PAGE_SIZE;
+	unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
+	unsigned long reloc_end = (unsigned long)__relocate_kernel_end;
 	unsigned long start_pgtable;
 	int result;
 
@@ -308,6 +310,8 @@ int machine_kexec_prepare(struct kimage *image)
 	if (result)
 		return result;
 
+	__memcpy(control_page, __relocate_kernel_start, reloc_end - reloc_start);
+
 	set_memory_x((unsigned long)control_page, 1);
 
 	return 0;
@@ -334,7 +338,6 @@ void machine_kexec(struct kimage *image)
 					     unsigned int preserve_context,
 					     unsigned int host_mem_enc_active);
 	unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
-	unsigned long reloc_end = (unsigned long)__relocate_kernel_end;
 	unsigned long page_list[PAGES_NR];
 	unsigned int host_mem_enc_active;
 	int save_ftrace_enabled;
@@ -372,7 +375,6 @@ void machine_kexec(struct kimage *image)
 	}
 
 	control_page = page_address(image->control_code_page) + PAGE_SIZE;
-	__memcpy(control_page, __relocate_kernel_start, reloc_end - reloc_start);
 
 	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
 	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
-- 
2.47.0