From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH v3 12/75] x86/boot/compressed/64: Switch to __KERNEL_CS after GDT is loaded Date: Tue, 28 Apr 2020 17:16:22 +0200 Message-ID: <20200428151725.31091-13-joro@8bytes.org> References: <20200428151725.31091-1-joro@8bytes.org> Return-path: In-Reply-To: <20200428151725.31091-1-joro@8bytes.org> Sender: kvm-owner@vger.kernel.org To: x86@kernel.org Cc: hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Thomas Hellstrom , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Joerg Roedel , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org From: Joerg Roedel When the pre-decompression code loads its first GDT in startup_64, it is still running on the CS value of the previous GDT. In the case of SEV-ES this is the EFI GDT. To make exception handling work (especially IRET) the CPU needs to switch to a CS value in the current GDT, so jump to __KERNEL_CS after the first GDT is loaded. Signed-off-by: Joerg Roedel --- arch/x86/boot/compressed/head_64.S | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 4f7e6b84be07..6b11060c3a0f 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -393,6 +393,14 @@ SYM_CODE_START(startup_64) addq %rax, 2(%rax) lgdt (%rax) + /* Reload CS so IRET returns to a CS actually in the GDT */ + pushq $__KERNEL_CS + leaq .Lon_kernel_cs(%rip), %rax + pushq %rax + lretq + +.Lon_kernel_cs: + /* * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. -- 2.17.1