From: Marc Zyngier <marc.zyngier@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Christoffer Dall <christoffer.dall@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu
Subject: [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist
Date: Wed, 3 Feb 2016 18:00:16 +0000 [thread overview]
Message-ID: <1454522416-6874-24-git-send-email-marc.zyngier@arm.com> (raw)
In-Reply-To: <1454522416-6874-1-git-send-email-marc.zyngier@arm.com>
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 <marc.zyngier@arm.com>
---
arch/arm64/include/asm/virt.h | 17 +++++++++++++++++
arch/arm64/kernel/head.S | 20 ++++++++++++++++++++
arch/arm64/kernel/smp.c | 3 +++
3 files changed, 40 insertions(+)
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 9f22dd6..f81a345 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[2];
+
void __hyp_set_vectors(phys_addr_t phys_vector_base);
phys_addr_t __hyp_get_vectors(void);
@@ -60,6 +65,18 @@ static inline bool is_kernel_in_hyp_mode(void)
return el == CurrentEL_EL2;
}
+static inline bool is_kernel_mode_mismatched(void)
+{
+ /*
+ * A mismatched CPU will have written its own CurrentEL in
+ * __run_cpu_mode[1] (initially set to zero) after failing to
+ * match the value in __run_cpu_mode[0]. Thus, a non-zero
+ * value in __run_cpu_mode[1] is enough to detect the
+ * pathological case.
+ */
+ return !!ACCESS_ONCE(__run_cpu_mode[1]);
+}
+
/* 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 6f2f377..f9b6a5b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -578,7 +578,24 @@ 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
+ cbz x0, skip_el_check
+ cmp x0, x20
+ bne mismatched_el
ret
+skip_el_check: // Only the first CPU gets to set the rule
+ str w20, [x1]
+ dmb sy
+ dc ivac, x1 // Invalidate potentially stale cache line
+ ret
+mismatched_el:
+ str w20, [x1, #4]
+ dmb sy
+ dc ivac, x1 // Invalidate potentially stale cache line
+1: wfi
+ b 1b
ENDPROC(set_cpu_boot_mode_flag)
/*
@@ -593,6 +610,9 @@ 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
+ .long 0
.popsection
/*
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index b1adc51..bc7650a 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -113,6 +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
next prev parent reply other threads:[~2016-02-03 18:01 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 17:59 [PATCH v3 00/23] arm64: Virtualization Host Extension support Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 01/23] arm/arm64: KVM: Add hook for C-based stage2 init Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 02/23] arm64: KVM: Switch to " Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 03/23] arm/arm64: Add new is_kernel_in_hyp_mode predicate Marc Zyngier
2016-02-08 14:41 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 04/23] arm64: Allow the arch timer to use the HYP timer Marc Zyngier
2016-02-03 17:59 ` [PATCH v3 05/23] arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature Marc Zyngier
2016-02-08 14:42 ` Catalin Marinas
2016-02-03 17:59 ` [PATCH v3 06/23] arm64: KVM: Skip HYP setup when already running in HYP Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 07/23] arm64: KVM: VHE: Patch out use of HVC Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 08/23] arm64: KVM: VHE: Patch out kern_hyp_va Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 09/23] arm64: KVM: VHE: Introduce unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 10/23] arm64: KVM: VHE: Differenciate host/guest sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 11/23] arm64: KVM: VHE: Split save/restore of registers shared between guest and host Marc Zyngier
2016-02-04 19:15 ` Christoffer Dall
2016-02-03 18:00 ` [PATCH v3 12/23] arm64: KVM: VHE: Use unified system register accessors Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 13/23] arm64: KVM: VHE: Enable minimal sysreg save/restore Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 14/23] arm64: KVM: VHE: Make __fpsimd_enabled VHE aware Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 15/23] arm64: KVM: VHE: Implement VHE activate/deactivate_traps Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 16/23] arm64: KVM: VHE: Use unified sysreg accessors for timer Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 17/23] arm64: KVM: VHE: Add fpsimd enabling on guest access Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 18/23] arm64: KVM: VHE: Add alternative panic handling Marc Zyngier
2016-02-03 18:00 ` [PATCH v3 19/23] arm64: KVM: Move most of the fault decoding to C Marc Zyngier
2016-02-04 19:20 ` Christoffer Dall
2016-02-08 14:44 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 20/23] arm64: perf: Count EL2 events if the kernel is running in HYP Marc Zyngier
2016-02-04 19:23 ` Christoffer Dall
2016-02-05 9:02 ` Marc Zyngier
2016-02-08 14:48 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 21/23] arm64: hw_breakpoint: Allow EL2 breakpoints if " Marc Zyngier
2016-02-08 15:56 ` Catalin Marinas
2016-02-08 16:45 ` Marc Zyngier
2016-02-08 16:52 ` Catalin Marinas
2016-02-03 18:00 ` [PATCH v3 22/23] arm64: VHE: Add support for running Linux in EL2 mode Marc Zyngier
2016-02-04 19:25 ` Christoffer Dall
2016-02-08 15:58 ` Catalin Marinas
2016-02-03 18:00 ` Marc Zyngier [this message]
2016-02-04 19:25 ` [PATCH v3 23/23] arm64: Panic when VHE and non VHE CPUs coexist Christoffer Dall
2016-02-08 16:04 ` Catalin Marinas
2016-02-08 16:24 ` Mark Rutland
2016-02-09 12:02 ` Catalin Marinas
2016-02-04 19:26 ` [PATCH v3 00/23] arm64: Virtualization Host Extension support Christoffer Dall
2016-02-05 8:56 ` Marc Zyngier
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