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SubjectRe: [PATCH] Fix undefined operation VMXOFF during reboot and crash
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Hi David,

If you happen to make a v2 of this patch, there are a few comments
that begin with "/**" but they are not kernel-doc comments, so they
should instead begin with just "/*". Please see below.

(and you did not introduce this comment style here.)

On 6/10/20 11:12 AM, David P. Reed wrote:
>
> Signed-off-by: David P. Reed <dpreed@deepplum.com>
> ---
> arch/x86/include/asm/virtext.h | 24 ++++++++++++----
> arch/x86/kernel/reboot.c | 13 ++-------
> arch/x86/kernel/traps.c | 52 ++++++++++++++++++++++++++++++++--
> 3 files changed, 71 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
> index 9aad0e0876fb..ea2d67191684 100644
> --- a/arch/x86/include/asm/virtext.h
> +++ b/arch/x86/include/asm/virtext.h
> @@ -13,12 +13,16 @@
> #ifndef _ASM_X86_VIRTEX_H
> #define _ASM_X86_VIRTEX_H
>
> +#include <linux/percpu.h>
> +
> #include <asm/processor.h>
>
> #include <asm/vmx.h>
> #include <asm/svm.h>
> #include <asm/tlbflush.h>
>
> +DECLARE_PER_CPU_READ_MOSTLY(int, doing_emergency_vmxoff);
> +
> /*
> * VMX functions:
> */
> @@ -33,8 +37,8 @@ static inline int cpu_has_vmx(void)
> /** Disable VMX on the current CPU

just
/* Disable VMX on the current CPU

> *
> * vmxoff causes a undefined-opcode exception if vmxon was not run
> - * on the CPU previously. Only call this function if you know VMX
> - * is enabled.
> + * on the CPU previously. Only call this function directly if you know VMX
> + * is enabled *and* CPU is in VMX root operation.
> */
> static inline void cpu_vmxoff(void)
> {
> @@ -47,17 +51,25 @@ static inline int cpu_vmx_enabled(void)
> return __read_cr4() & X86_CR4_VMXE;
> }
>
> -/** Disable VMX if it is enabled on the current CPU
> +/** Force disable VMX if it is enabled on the current CPU.

just
/* Force disable VMX if it is enabled on the current CPU.

> + * Note that if CPU is not in VMX root operation this
> + * VMXOFF will fault an undefined operation fault.
> + * So the 'doing_emergency_vmxoff' percpu flag is set,
> + * the trap handler for just restarts execution after
> + * the VMXOFF instruction.
> *
> - * You shouldn't call this if cpu_has_vmx() returns 0.
> + * You shouldn't call this directly if cpu_has_vmx() returns 0.
> */
> static inline void __cpu_emergency_vmxoff(void)
> {
> - if (cpu_vmx_enabled())
> + if (cpu_vmx_enabled()) {
> + this_cpu_write(doing_emergency_vmxoff, 1);
> cpu_vmxoff();
> + this_cpu_write(doing_emergency_vmxoff, 0);
> + }
> }
>
> -/** Disable VMX if it is supported and enabled on the current CPU
> +/** Force disable VMX if it is supported and enabled on the current CPU

ditto.


> */
> static inline void cpu_emergency_vmxoff(void)
> {


thanks.
--
~Randy

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