linux-kernel - Re: [BUG][SEVERE] Enabling EFI runtime services causes panics in the T2 security chip on Macs equipped with it.

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Date:   Wed, 12 Jan 2022 06:23:29 +0000
From:   Aditya Garg <gargaditya08@...e.com>
To:     Ard Biesheuvel <ardb@...nel.org>
CC:     "jk@...abs.org" <jk@...abs.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Orlando Chamberlain <redecorating@...tonmail.com>,
        Aun-Ali Zaidi <admin@...eit.net>
Subject: Re: [BUG][SEVERE] Enabling EFI runtime services causes panics in the
 T2 security chip on Macs equipped with it.

Hi Ard
As I said before, if I apply the patch below, the things work well
> 
> Can you check whether things work as before after applying the change below?
> 
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 147c30a81f15..d7203355cc69 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -399,7 +399,7 @@ static int __init efi_systab_init(unsigned long phys)
>                efi_nr_tables           = systab32->nr_tables;
>        }
> 
> -       efi.runtime_version = hdr->revision;
> +       efi.runtime_version = EFI_1_10_SYSTEM_TABLE_REVISION;
> 
>        efi_systab_report_header(hdr, efi_fw_vendor);
>        early_memunmap(p, size);

Now, I tried to quirk on the basis of DMI data for some t2 Macs using this patch :-

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 147c30a81..0d73d7709 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -44,6 +44,7 @@
 #include <linux/io.h>
 #include <linux/reboot.h>
 #include <linux/bcd.h>
+#include <linux/dmi.h>
 
 #include <asm/setup.h>
 #include <asm/efi.h>
@@ -339,6 +340,52 @@ void __init efi_print_memmap(void)
 	}
 }
 
+static const struct dmi_system_id apple_use_old_runtime_version[] = {
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,1"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,2"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,4"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookAir8,1"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookAir8,2"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "iMac20,1"),
+		},
+	},
+	{
+		 .matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "iMac20,2"),
+		},
+	},
+	{ }
+};
+
 static int __init efi_systab_init(unsigned long phys)
 {
 	int size = efi_enabled(EFI_64BIT) ? sizeof(efi_system_table_64_t)
@@ -347,6 +394,7 @@ static int __init efi_systab_init(unsigned long phys)
 	bool over4g = false;
 	void *p;
 	int ret;
+	const struct dmi_system_id *dmi_id;
 
 	hdr = p = early_memremap_ro(phys, size);
 	if (p == NULL) {
@@ -398,8 +446,15 @@ static int __init efi_systab_init(unsigned long phys)
 		efi_config_table	= systab32->tables;
 		efi_nr_tables		= systab32->nr_tables;
 	}
-
-	efi.runtime_version = hdr->revision;
+	
+	dmi_id = dmi_first_match(apple_use_old_runtime_version);
+	if (dmi_id) {
+		efi.runtime_version = EFI_1_10_SYSTEM_TABLE_REVISION;
+		pr_info("T2 Mac detected. Using runtime service version 1.10\n");
+	}
+	else {
+		efi.runtime_version = hdr->revision;
+	}
 
 	efi_systab_report_header(hdr, efi_fw_vendor);
 	early_memunmap(p, size);
-- 
2.25.1

But, now the issue doesn't seen to get resolved
Could you help me in this?