Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759477AbbGHQTv (ORCPT ); Wed, 8 Jul 2015 12:19:51 -0400 Received: from foss.arm.com ([217.140.101.70]:42183 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759442AbbGHQTq (ORCPT ); Wed, 8 Jul 2015 12:19:46 -0400 From: Marc Zyngier To: Catalin Marinas , Will Deacon , Christoffer Dall Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: [PATCH 11/13] arm64: Panic when VHE and non VHE CPUs coexist Date: Wed, 8 Jul 2015 17:19:14 +0100 Message-Id: <1436372356-30410-12-git-send-email-marc.zyngier@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1436372356-30410-1-git-send-email-marc.zyngier@arm.com> References: <1436372356-30410-1-git-send-email-marc.zyngier@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3515 Lines: 121 Having both VHE and non-VHE capable CPUs in the same system is likely to be a recipe for disaster. If the boot CPU has VHE, but a secondary is not, we won't be able to downgrade and run the kernel at EL1. Add CPU hotplug to the mix, and this produces a terrifying mess. Let's solve the problem once and for all. If you mix VHE and non-VHE CPUs in the same system, you deserve to loose, and this patch makes sure you don't get a chance. This is implemented by storing the kernel execution level in a global variable. Secondaries will park themselves in a WFI loop if they observe a mismatch. Also, the primary CPU will detect that the secondary CPU has died on a mismatched execution level. Panic will follow. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/virt.h | 15 +++++++++++++++ arch/arm64/kernel/head.S | 15 +++++++++++++++ arch/arm64/kernel/smp.c | 4 ++++ 3 files changed, 34 insertions(+) diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 9f22dd6..8e246f7 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -36,6 +36,11 @@ */ extern u32 __boot_cpu_mode[2]; +/* + * __run_cpu_mode records the mode the boot CPU uses for the kernel. + */ +extern u32 __run_cpu_mode; + void __hyp_set_vectors(phys_addr_t phys_vector_base); phys_addr_t __hyp_get_vectors(void); @@ -60,6 +65,16 @@ static inline bool is_kernel_in_hyp_mode(void) return el == CurrentEL_EL2; } +static inline bool is_kernel_mode_mismatched(void) +{ + u64 el; + u32 mode; + + asm("mrs %0, CurrentEL" : "=r" (el)); + mode = ACCESS_ONCE(__run_cpu_mode); + return el != mode; +} + /* The section containing the hypervisor text */ extern char __hyp_text_start[]; extern char __hyp_text_end[]; diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index a179747..318e69f 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -578,7 +578,20 @@ ENTRY(set_cpu_boot_mode_flag) 1: str w20, [x1] // This CPU has booted in EL1 dmb sy dc ivac, x1 // Invalidate potentially stale cache line + adr_l x1, __run_cpu_mode + ldr w0, [x1] + mrs x20, CurrentEL + str w20, [x1] + dmb sy + dc ivac, x1 // Invalidate potentially stale cache line + cbz x0, skip_el_check + cmp x0, x20 + bne mismatched_el +skip_el_check: ret +mismatched_el: + wfi + b mismatched_el ENDPROC(set_cpu_boot_mode_flag) /* @@ -593,6 +606,8 @@ ENDPROC(set_cpu_boot_mode_flag) ENTRY(__boot_cpu_mode) .long BOOT_CPU_MODE_EL2 .long BOOT_CPU_MODE_EL1 +ENTRY(__run_cpu_mode) + .long 0 .popsection #ifdef CONFIG_SMP diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 695801a..b467f51 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -52,6 +52,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -112,6 +113,9 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) pr_crit("CPU%u: failed to come online\n", cpu); ret = -EIO; } + + if (is_kernel_mode_mismatched()) + panic("CPU%u: incompatible execution level", cpu); } else { pr_err("CPU%u: failed to boot: %d\n", cpu, ret); } -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/