linux-kernel - Re: [PATCH v1 0/2] firmware: dmi_scan: Make it work in kexec'ed kernel

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Date:   Sat, 12 Jun 2021 12:40:57 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jean Delvare <jdelvare@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Javier Tiá <javier.tia@...il.com>,
        kexec@...ts.infradead.org, Eric Biederman <ebiederm@...ssion.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v1 0/2] firmware: dmi_scan: Make it work in kexec'ed
 kernel

> Probably it is doable to have kexec on 32bit efi working
> without runtime service support, that means no need the trick of fixed
> mapping.
> 
> If I can restore my vm to boot 32bit efi on this weekend then I may provide some draft
> patches for test.

Unfortunately I failed to setup a 32bit efi guest,  here are some
untested draft patches, please have a try.

========= kernel draft patch ==============

---
 arch/x86/boot/header.S         |    2 +-
 arch/x86/platform/efi/efi.c    |    6 +++---
 arch/x86/platform/efi/quirks.c |    3 ---
 3 files changed, 4 insertions(+), 7 deletions(-)

--- linux-x86.orig/arch/x86/boot/header.S
+++ linux-x86/arch/x86/boot/header.S
@@ -416,7 +416,7 @@ xloadflags:
 # define XLF23 0
 #endif
 
-#if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
+#if defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
 # define XLF4 XLF_EFI_KEXEC
 #else
 # define XLF4 0
--- linux-x86.orig/arch/x86/platform/efi/efi.c
+++ linux-x86/arch/x86/platform/efi/efi.c
@@ -710,10 +710,10 @@ static void __init kexec_enter_virtual_m
 	unsigned int num_pages;
 
 	/*
-	 * We don't do virtual mode, since we don't do runtime services, on
-	 * non-native EFI.
+	 * We don't do virtual mode, since we don't do runtime services
+	 * on non-native or IA32 EFI.
 	 */
-	if (efi_is_mixed()) {
+	if (!efi_enabled(EFI_64BIT)) {
 		efi_memmap_unmap();
 		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 		return;
--- linux-x86.orig/arch/x86/platform/efi/quirks.c
+++ linux-x86/arch/x86/platform/efi/quirks.c
@@ -524,9 +524,6 @@ int __init efi_reuse_config(u64 tables,
 	if (!efi_setup)
 		return 0;
 
-	if (!efi_enabled(EFI_64BIT))
-		return 0;
-
 	data = early_memremap(efi_setup, sizeof(*data));
 	if (!data) {
 		ret = -ENOMEM;


========= kexec-tools draft patch =========

---
 kexec/arch/i386/kexec-bzImage.c |    5 +++++
 1 file changed, 5 insertions(+)

--- kexec-tools.orig/kexec/arch/i386/kexec-bzImage.c
+++ kexec-tools/kexec/arch/i386/kexec-bzImage.c
@@ -83,6 +83,11 @@ int bzImage_probe(const char *buf, off_t
 	if (probe_debug) {
 		fprintf(stderr, "It's a bzImage\n");
 	}
+
+#define XLF_EFI_KEXEC   (1 << 4)
+	if ((header->xloadflags & XLF_EFI_KEXEC) == XLF_EFI_KEXEC)
+		bzImage_support_efi_boot = 1;
+
 	return 0;
 }