From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1g5VZo-0000Gd-MB for kexec@lists.infradead.org; Thu, 27 Sep 2018 12:39:30 +0000 From: Kairui Song Subject: [PATCH] x86/boot: Fix kexec booting failure after SEV early boot support Date: Thu, 27 Sep 2018 20:38:45 +0800 Message-Id: <20180927123845.32052-1-kasong@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: linux-kernel@vger.kernel.org Cc: thomas.lendacky@amd.com, ghook@redhat.com, brijesh.singh@amd.com, kasong@redhat.com, bhe@redhat.com, x86@kernel.org, kexec@lists.infradead.org, mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de, bp@suse.de, dyoung@redhat.com Commit 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active") is causing kexec becomes sometimes unstable even if SEV is not active. kexec reboot won't start a second kernel bypassing BIOS boot process, instead, the system got reset. That's because, in get_sev_encryption_bit function, we are using 32-bit RIP-relative addressing to read the value of enc_bit, but kexec may alloc the early boot up code to a higher location, which is beyond 32-bit addressing limit. Some garbage will be read and get_sev_encryption_bit will return the wrong value, which leads to wrong memory page flag. This patch removes the use of enc_bit, as currently, enc_bit's only purpose is to avoid duplicated encryption bit reading, but the overhead of reading encryption bit is so tiny, so no need to cache that. Fixes: 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active") Suggested-by: Borislav Petkov Signed-off-by: Kairui Song --- arch/x86/boot/compressed/mem_encrypt.S | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S index eaa843a52907..a480356e0ed8 100644 --- a/arch/x86/boot/compressed/mem_encrypt.S +++ b/arch/x86/boot/compressed/mem_encrypt.S @@ -25,20 +25,6 @@ ENTRY(get_sev_encryption_bit) push %ebx push %ecx push %edx - push %edi - - /* - * RIP-relative addressing is needed to access the encryption bit - * variable. Since we are running in 32-bit mode we need this call/pop - * sequence to get the proper relative addressing. - */ - call 1f -1: popl %edi - subl $1b, %edi - - movl enc_bit(%edi), %eax - cmpl $0, %eax - jge .Lsev_exit /* Check if running under a hypervisor */ movl $1, %eax @@ -69,15 +55,12 @@ ENTRY(get_sev_encryption_bit) movl %ebx, %eax andl $0x3f, %eax /* Return the encryption bit location */ - movl %eax, enc_bit(%edi) jmp .Lsev_exit .Lno_sev: xor %eax, %eax - movl %eax, enc_bit(%edi) .Lsev_exit: - pop %edi pop %edx pop %ecx pop %ebx @@ -113,8 +96,6 @@ ENTRY(set_sev_encryption_mask) ENDPROC(set_sev_encryption_mask) .data -enc_bit: - .int 0xffffffff #ifdef CONFIG_AMD_MEM_ENCRYPT .balign 8 -- 2.17.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec