[PATCH 08/18] arm64: kexec: skip relocation code for inplace kexec

From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, jmorris@namei.org, sashal@kernel.org,
	ebiederm@xmission.com, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, corbet@lwn.net,
	catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, maz@kernel.org,
	james.morse@arm.com, vladimir.murzin@arm.com,
	matthias.bgg@gmail.com, linux-mm@kvack.org, mark.rutland@arm.com,
	steve.capper@arm.com, rfontana@redhat.com, tglx@linutronix.de,
	selindag@gmail.com, tyhicks@linux.microsoft.com,
	kernelfans@gmail.com, akpm@linux-foundation.org,
	madvenka@linux.microsoft.com
Subject: [PATCH 08/18] arm64: kexec: skip relocation code for inplace kexec
Date: Thu, 27 May 2021 11:05:16 -0400	[thread overview]
Message-ID: <20210527150526.271941-9-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20210527150526.271941-1-pasha.tatashin@soleen.com>

In case of kdump or when segments are already in place the relocation
is not needed, therefore the setup of relocation function and call to
it can be skipped.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Suggested-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/machine_kexec.c   | 34 ++++++++++++++++++-----------
 arch/arm64/kernel/relocate_kernel.S |  3 ---
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 3a034bc25709..bde623805866 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -139,21 +139,23 @@ int machine_kexec_post_load(struct kimage *kimage)
 {
 	void *reloc_code = page_to_virt(kimage->control_code_page);
 
-	/* If in place flush new kernel image, else flush lists and buffers */
-	if (kimage->head & IND_DONE)
+	/* If in place, relocation is not used, only flush next kernel */
+	if (kimage->head & IND_DONE) {
 		kexec_segment_flush(kimage);
-	else
-		kexec_list_flush(kimage);
+		kexec_image_info(kimage);
+		return 0;
+	}
 
 	memcpy(reloc_code, arm64_relocate_new_kernel,
 	       arm64_relocate_new_kernel_size);
 	kimage->arch.kern_reloc = __pa(reloc_code);
-	kexec_image_info(kimage);
 
 	/* Flush the reloc_code in preparation for its execution. */
 	__flush_dcache_area(reloc_code, arm64_relocate_new_kernel_size);
 	flush_icache_range((uintptr_t)reloc_code, (uintptr_t)reloc_code +
 			   arm64_relocate_new_kernel_size);
+	kexec_list_flush(kimage);
+	kexec_image_info(kimage);
 
 	return 0;
 }
@@ -180,19 +182,25 @@ void machine_kexec(struct kimage *kimage)
 	local_daif_mask();
 
 	/*
-	 * cpu_soft_restart will shutdown the MMU, disable data caches, then
-	 * transfer control to the kern_reloc which contains a copy of
-	 * the arm64_relocate_new_kernel routine.  arm64_relocate_new_kernel
-	 * uses physical addressing to relocate the new image to its final
-	 * position and transfers control to the image entry point when the
-	 * relocation is complete.
+	 * Both restart and cpu_soft_restart will shutdown the MMU, disable data
+	 * caches. However, restart will start new kernel or purgatory directly,
+	 * cpu_soft_restart will transfer control to arm64_relocate_new_kernel
 	 * In kexec case, kimage->start points to purgatory assuming that
 	 * kernel entry and dtb address are embedded in purgatory by
 	 * userspace (kexec-tools).
 	 * In kexec_file case, the kernel starts directly without purgatory.
 	 */
-	cpu_soft_restart(kimage->arch.kern_reloc, kimage->head, kimage->start,
-			 kimage->arch.dtb_mem);
+	if (kimage->head & IND_DONE) {
+		typeof(__cpu_soft_restart) *restart;
+
+		cpu_install_idmap();
+		restart = (void *)__pa_symbol(function_nocfi(__cpu_soft_restart));
+		restart(is_hyp_callable(), kimage->start, kimage->arch.dtb_mem,
+			0, 0);
+	} else {
+		cpu_soft_restart(kimage->arch.kern_reloc, kimage->head,
+				 kimage->start, kimage->arch.dtb_mem);
+	}
 
 	BUG(); /* Should never get here. */
 }
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index b78ea5de97a4..8058fabe0a76 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -32,8 +32,6 @@ SYM_CODE_START(arm64_relocate_new_kernel)
 	mov	x16, x0				/* x16 = kimage_head */
 	mov	x14, xzr			/* x14 = entry ptr */
 	mov	x13, xzr			/* x13 = copy dest */
-	/* Check if the new image needs relocation. */
-	tbnz	x16, IND_DONE_BIT, .Ldone
 	raw_dcache_line_size x15, x1		/* x15 = dcache line size */
 .Lloop:
 	and	x12, x16, PAGE_MASK		/* x12 = addr */
@@ -65,7 +63,6 @@ SYM_CODE_START(arm64_relocate_new_kernel)
 .Lnext:
 	ldr	x16, [x14], #8			/* entry = *ptr++ */
 	tbz	x16, IND_DONE_BIT, .Lloop	/* while (!(entry & DONE)) */
-.Ldone:
 	/* wait for writes from copy_page to finish */
 	dsb	nsh
 	ic	iallu
-- 
2.25.1


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