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From: Marc Zyngier <maz@kernel.org>
To: Michael Kelley <mikelley@microsoft.com>
Cc: will@kernel.org, ardb@kernel.org, arnd@arndb.de,
	catalin.marinas@arm.com, mark.rutland@arm.com,
	linux-arm-kernel@lists.infradead.org, gregkh@linuxfoundation.org,
	linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
	linux-efi@vger.kernel.org, linux-arch@vger.kernel.org,
	olaf@aepfle.de, apw@canonical.com, vkuznets@redhat.com,
	jasowang@redhat.com, marcelo.cerri@canonical.com,
	kys@microsoft.com, sunilmut@microsoft.com, boqun.feng@gmail.com
Subject: Re: [PATCH v6 06/10] arm64: hyperv: Add kexec and panic handlers
Date: Sun, 15 Mar 2020 18:15:44 +0000
Message-ID: <86tv2pzdpr.wl-maz@kernel.org> (raw)
In-Reply-To: <1584200119-18594-7-git-send-email-mikelley@microsoft.com>

On Sat, 14 Mar 2020 15:35:15 +0000,
Michael Kelley <mikelley@microsoft.com> wrote:
> 
> Add functions to set up and remove kexec and panic
> handlers, and to inform Hyper-V about a guest panic.
> These functions are called from architecture independent
> code in the VMbus driver.
> 
> This code is built only when CONFIG_HYPERV is enabled.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  arch/arm64/hyperv/hv_core.c  | 61 ++++++++++++++++++++++++++++++++++++++++++++
>  arch/arm64/hyperv/mshyperv.c | 26 +++++++++++++++++++
>  2 files changed, 87 insertions(+)
> 
> diff --git a/arch/arm64/hyperv/hv_core.c b/arch/arm64/hyperv/hv_core.c
> index 4aa6b8f..8d6de9f 100644
> --- a/arch/arm64/hyperv/hv_core.c
> +++ b/arch/arm64/hyperv/hv_core.c
> @@ -199,3 +199,64 @@ void hv_get_vpreg_128(u32 msr, struct hv_get_vp_register_output *res)
>  	kfree(output);
>  }
>  EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
> +
> +void hyperv_report_panic(struct pt_regs *regs, long err)
> +{
> +	static bool panic_reported;
> +	u64 guest_id;
> +
> +	/*
> +	 * We prefer to report panic on 'die' chain as we have proper
> +	 * registers to report, but if we miss it (e.g. on BUG()) we need
> +	 * to report it on 'panic'.
> +	 */
> +	if (panic_reported)
> +		return;
> +	panic_reported = true;

How does this work when multiple vcpus are crashing at once? Are you
guaranteed to be single-threaded at this point?

> +
> +	guest_id = hv_get_vpreg(HV_REGISTER_GUEST_OSID);
> +
> +	/*
> +	 * Hyper-V provides the ability to store only 5 values.
> +	 * Pick the passed in error value, the guest_id, and the PC.
> +	 * The first two general registers are added arbitrarily.
> +	 */
> +	hv_set_vpreg(HV_REGISTER_CRASH_P0, err);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P1, guest_id);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P2, regs->pc);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P3, regs->regs[0]);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P4, regs->regs[1]);

How about reporting useful information, a pointer to some data
structure describing the fault? As it is, the usefulness of this is
pretty dubious.

> +
> +	/*
> +	 * Let Hyper-V know there is crash data available
> +	 */
> +	hv_set_vpreg(HV_REGISTER_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
> +}
> +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.
> +	 */
> +	hv_set_vpreg(HV_REGISTER_CRASH_P0, 0);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P1, 0);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P2, 0);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P3, pa);
> +	hv_set_vpreg(HV_REGISTER_CRASH_P4, size);
> +
> +	/*
> +	 * Let Hyper-V know there is crash data available along with
> +	 * the panic message.
> +	 */
> +	hv_set_vpreg(HV_REGISTER_CRASH_CTL,
> +	       (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
> +}
> +EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> index ae6ece6..c58940d 100644
> --- a/arch/arm64/hyperv/mshyperv.c
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -23,6 +23,8 @@
>  
>  static void (*vmbus_handler)(void);
>  static void (*hv_stimer0_handler)(void);
> +static void (*hv_kexec_handler)(void);
> +static void (*hv_crash_handler)(struct pt_regs *regs);

Why is this in the arch-specific code? Yes, it lives in the x86 arch
code too, but I don't see what prevents it from being moved to the
vmbus_drv.c code.

>  
>  static int vmbus_irq;
>  static long __percpu *vmbus_evt;
> @@ -137,3 +139,27 @@ void hv_remove_stimer0_irq(int irq)
>  	}
>  }
>  EXPORT_SYMBOL_GPL(hv_remove_stimer0_irq);
> +
> +void hv_setup_kexec_handler(void (*handler)(void))
> +{
> +	hv_kexec_handler = handler;
> +}
> +EXPORT_SYMBOL_GPL(hv_setup_kexec_handler);
> +
> +void hv_remove_kexec_handler(void)
> +{
> +	hv_kexec_handler = NULL;
> +}
> +EXPORT_SYMBOL_GPL(hv_remove_kexec_handler);
> +
> +void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
> +{
> +	hv_crash_handler = handler;
> +}
> +EXPORT_SYMBOL_GPL(hv_setup_crash_handler);
> +
> +void hv_remove_crash_handler(void)
> +{
> +	hv_crash_handler = NULL;
> +}
> +EXPORT_SYMBOL_GPL(hv_remove_crash_handler);
> -- 
> 1.8.3.1
> 
> 

Thanks,

	M.

-- 
Jazz is not dead, it just smells funny.

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-14 15:35 [PATCH v6 00/10] Subject: Enable Linux guests on Hyper-V on ARM64 Michael Kelley
2020-03-14 15:35 ` [PATCH v6 01/10] arm64: hyperv: Add core Hyper-V include files Michael Kelley
2020-03-15 17:31   ` Marc Zyngier
2020-03-18  0:10     ` Michael Kelley
2020-03-16  8:47   ` Arnd Bergmann
2020-03-18  0:12     ` Michael Kelley
2020-03-18 10:10       ` Arnd Bergmann
2020-03-19 21:31         ` Michael Kelley
2020-03-20 16:38           ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 02/10] arm/arm64: smccc-1.1: Add vendor specific owner definition Michael Kelley
2020-03-14 15:35 ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley
2020-03-14 15:35 ` [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages Michael Kelley
2020-03-16  8:22   ` Arnd Bergmann
2020-03-16  8:30     ` gregkh
2020-03-16  8:30     ` Marc Zyngier
2020-03-16  8:32       ` Arnd Bergmann
2020-03-18  0:15         ` Michael Kelley
2020-03-18  9:57           ` Arnd Bergmann
2020-03-19 21:43             ` Michael Kelley
2020-03-20 16:28               ` Arnd Bergmann
2020-03-20 17:22                 ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 05/10] arm64: hyperv: Add interrupt handlers for VMbus and stimer Michael Kelley
2020-03-16  8:25   ` Arnd Bergmann
2020-03-18  0:16     ` Michael Kelley
2020-03-18  9:52       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 06/10] arm64: hyperv: Add kexec and panic handlers Michael Kelley
2020-03-15 18:15   ` Marc Zyngier [this message]
2020-03-18  0:17     ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 07/10] arm64: hyperv: Initialize hypervisor on boot Michael Kelley
2020-03-16  8:29   ` Arnd Bergmann
2020-03-18  0:17     ` Michael Kelley
2020-03-18  9:44       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 08/10] Drivers: hv: vmbus: Add hooks for per-CPU IRQ Michael Kelley
2020-03-14 15:35 ` [PATCH v6 09/10] arm64: efi: Export screen_info Michael Kelley
2020-03-16  8:20   ` Arnd Bergmann
2020-03-18  0:18     ` Michael Kelley
2020-03-18  9:26       ` Arnd Bergmann
2020-03-19 21:46         ` Michael Kelley
2020-05-13 14:26           ` Nikhil Mahale
2020-05-18  4:25             ` Nikhil Mahale
2020-05-18 12:51               ` Ard Biesheuvel
2020-05-22 11:14                 ` Nikhil Mahale
2020-05-22 11:32                   ` Ard Biesheuvel
2020-03-14 15:35 ` [PATCH v6 10/10] Drivers: hv: Enable Hyper-V code to be built on ARM64 Michael Kelley
     [not found] ` <20200318031130.5476-1-hdanton@sina.com>
2020-03-19 21:04   ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley

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