linux-kernel - [RFC v1 8/8] crash hp: Add x86 crash hotplug support for bzImage

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Date:   Thu, 18 Nov 2021 12:49:48 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
        eric.devolder@...cle.com
Subject: [RFC v1 8/8] crash hp: Add x86 crash hotplug support for bzImage

The few changes to kexec-bzimage64.c are to record information needed
in advance of when a hotplug event occurs. This information is recorded
when the crash/capture kernel is loaded.

In particular, the index of the purgatory segment, and the handful of
register context values needed by purgatory, are recorded.

Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 170d0fd68b1f..1886c215215d 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -378,6 +378,10 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	 * Load purgatory. For 64bit entry point, purgatory  code can be
 	 * anywhere.
 	 */
+#ifdef CONFIG_CRASH_HOTPLUG
+	/* Record the index of the purgatory segment */
+	image->arch.hp.purg_index = image->nr_segments;
+#endif
 	ret = kexec_load_purgatory(image, &pbuf);
 	if (ret) {
 		pr_err("Loading purgatory failed\n");
@@ -488,6 +492,14 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	if (ret)
 		goto out_free_params;
 
+#ifdef CONFIG_CRASH_HOTPLUG
+	/* Save for use on hotplug to patch up purgatory context */
+	image->arch.hp.rbx = regs64.rbx;
+	image->arch.hp.rsi = regs64.rsi;
+	image->arch.hp.rip = regs64.rip;
+	image->arch.hp.rsp = regs64.rsp;
+#endif
+
 	ret = setup_boot_parameters(image, params, bootparam_load_addr,
 				    efi_map_offset, efi_map_sz,
 				    efi_setup_data_offset);
-- 
2.27.0