Messages in this thread Patch in this message | | | From | Marc Zyngier <> | Subject | [PATCH 4/5] arm64: Warn on booting at EL2 with HVC disabled | Date | Thu, 12 Aug 2021 20:02:12 +0100 |
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Now that we are able to paper over the gigantic stupidity that booting at EL2 with SCR_EL3.HCE==0 is, let's taint WARN_TAINT() when detecting this situation.
Yes, this is *LOUD*.
Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/include/asm/virt.h | 10 ++++++++++ arch/arm64/kernel/head.S | 10 ++++++++++ arch/arm64/kernel/smp.c | 3 +++ 3 files changed, 23 insertions(+)
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 7379f35ae2c6..89bf5ae522da 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -49,6 +49,9 @@ #define BOOT_CPU_MODE_EL1 (0xe11) #define BOOT_CPU_MODE_EL2 (0xe12) +/* Flags associated to the boot mode */ +#define BOOT_CPU_MODE_DOWNGRADED (1 << 0) + #ifndef __ASSEMBLY__ #include <asm/ptrace.h> @@ -67,6 +70,13 @@ */ extern u32 __boot_cpu_mode[2]; +/* + * __boot_cpu_mode_flags records events that are associated with CPUs + * coming online. A CPU having been downgraded from EL2 to EL1 because + * of HVC not being enabled will have BOOT_CPU_MODE_DOWNGRADED set. + */ +extern u32 __boot_cpu_mode_flags[1]; + void __hyp_set_vectors(phys_addr_t phys_vector_base); void __hyp_reset_vectors(void); diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index d6b2b05f5d3a..fdad6805868b 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -530,7 +530,13 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL) /* * HVC is unusable, so pretend we actually booted at EL1. * Once we have left EL2, there will be no going back. + * set_cpu_boot_mode_flag will do the necessary CMOs for us. */ + adr_l x1, __boot_cpu_mode_flags + ldr w0, [x1] + orr w0, w0, BOOT_CPU_MODE_DOWNGRADED + str w0, [x1] + mov_q x0, INIT_SCTLR_EL1_MMU_OFF msr sctlr_el1, x0 @@ -623,6 +629,10 @@ SYM_DATA_START(__early_cpu_boot_status) .quad 0 SYM_DATA_END(__early_cpu_boot_status) +SYM_DATA_START(__boot_cpu_mode_flags) + .long 0 +SYM_DATA_END(__boot_cpu_mode_flags) + .popsection /* diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 6f6ff072acbd..43fad7ca9110 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -425,6 +425,9 @@ static void __init hyp_mode_check(void) else if (is_hyp_mode_mismatched()) WARN_TAINT(1, TAINT_CPU_OUT_OF_SPEC, "CPU: CPUs started in inconsistent modes"); + else if (__boot_cpu_mode_flags[0] & BOOT_CPU_MODE_DOWNGRADED) + WARN_TAINT(1, TAINT_CPU_OUT_OF_SPEC, + "CPU: CPUs downgraded to EL1, HVC disabled"); else pr_info("CPU: All CPU(s) started at EL1\n"); if (IS_ENABLED(CONFIG_KVM) && !is_kernel_in_hyp_mode()) { -- 2.30.2
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