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Date:   Mon, 22 Feb 2021 11:27:00 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     sthemmin@...rosoft.com, kys@...rosoft.com, wei.liu@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        daniel.lezcano@...aro.org, arnd@...db.de,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 04/10] Drivers: hv: vmbus: Move hyperv_report_panic_msg
 to arch neutral code

On Wed, Jan 27, 2021 at 12:23:39PM -0800, Michael Kelley wrote:
> With the new Hyper-V MSR set function, hyperv_report_panic_msg() can be
> architecture neutral, so move it out from under arch/x86 and merge into
> hv_kmsg_dump(). This move also avoids needing a separate implementation
> under arch/arm64.
> 
> No functional change.
> 
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  arch/x86/hyperv/hv_init.c      | 27 ---------------------------
>  drivers/hv/vmbus_drv.c         | 24 +++++++++++++++++++-----
>  include/asm-generic/mshyperv.h |  1 -
>  3 files changed, 19 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 9b2cdbe..22e9557 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -452,33 +452,6 @@ void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
>  }
>  EXPORT_SYMBOL_GPL(hyperv_report_panic);
>  
> -/**
> - * hyperv_report_panic_msg - report panic message to Hyper-V
> - * @pa: physical address of the panic page containing the message
> - * @size: size of the message in the page
> - */
> -void hyperv_report_panic_msg(phys_addr_t pa, size_t size)
> -{
> -	/*
> -	 * P3 to contain the physical address of the panic page & P4 to
> -	 * contain the size of the panic data in that page. Rest of the
> -	 * registers are no-op when the NOTIFY_MSG flag is set.
> -	 */
> -	wrmsrl(HV_X64_MSR_CRASH_P0, 0);
> -	wrmsrl(HV_X64_MSR_CRASH_P1, 0);
> -	wrmsrl(HV_X64_MSR_CRASH_P2, 0);
> -	wrmsrl(HV_X64_MSR_CRASH_P3, pa);
> -	wrmsrl(HV_X64_MSR_CRASH_P4, size);
> -
> -	/*
> -	 * Let Hyper-V know there is crash data available along with
> -	 * the panic message.
> -	 */
> -	wrmsrl(HV_X64_MSR_CRASH_CTL,
> -	       (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
> -}
> -EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);
> -
>  bool hv_is_hyperv_initialized(void)
>  {
>  	union hv_x64_msr_hypercall_contents hypercall_msr;
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 089f165..8affe68 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1365,22 +1365,36 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper,
>  			 enum kmsg_dump_reason reason)
>  {
>  	size_t bytes_written;
> -	phys_addr_t panic_pa;
>  
>  	/* We are only interested in panics. */
>  	if ((reason != KMSG_DUMP_PANIC) || (!sysctl_record_panic_msg))
>  		return;
>  
> -	panic_pa = virt_to_phys(hv_panic_page);
> -
>  	/*
>  	 * Write dump contents to the page. No need to synchronize; panic should
>  	 * be single-threaded.
>  	 */
>  	kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE,
>  			     &bytes_written);
> -	if (bytes_written)
> -		hyperv_report_panic_msg(panic_pa, bytes_written);
> +	if (!bytes_written)
> +		return;
> +	/*
> +	 * P3 to contain the physical address of the panic page & P4 to
> +	 * contain the size of the panic data in that page. Rest of the
> +	 * registers are no-op when the NOTIFY_MSG flag is set.
> +	 */
> +	hv_set_register(HV_REGISTER_CRASH_P0, 0);
> +	hv_set_register(HV_REGISTER_CRASH_P1, 0);
> +	hv_set_register(HV_REGISTER_CRASH_P2, 0);
> +	hv_set_register(HV_REGISTER_CRASH_P3, virt_to_phys(hv_panic_page));
> +	hv_set_register(HV_REGISTER_CRASH_P4, bytes_written);
> +
> +	/*
> +	 * Let Hyper-V know there is crash data available along with
> +	 * the panic message.
> +	 */
> +	hv_set_register(HV_REGISTER_CRASH_CTL,
> +	       (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
>  }
>  
>  static struct kmsg_dumper hv_kmsg_dumper = {
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 10c97a9..6a8072f 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -170,7 +170,6 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
>  }
>  
>  void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
> -void hyperv_report_panic_msg(phys_addr_t pa, size_t size);
>  bool hv_is_hyperv_initialized(void);
>  bool hv_is_hibernation_supported(void);
>  void hyperv_cleanup(void);
> -- 
> 1.8.3.1
> 

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