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Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic

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In the VM mode on Hyper-V, currently, when the kernel panics, an error
code and few register values are populated in an MSR and the Hypervisor
notified. This information is collected on the host. The amount of
information currently collected is found to be limited and not very
actionable. To gather more actionable data, such as stack trace, the
proposal is to write one page worth of kmsg data on an allocated page
and the Hypervisor notified of the page address through the MSR.

- Sysctl option to control the behavior, with ON by default.

Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sunil Muthuswamy
2018-07-08 02:56:51 +00:00
committed by Greg Kroah-Hartman
parent e464d28273
commit 81b18bce48
5 changed files with 152 additions and 2 deletions
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27
arch/x86/hyperv/hv_init.c
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@@ -423,6 +423,33 @@ void hyperv_report_panic(struct pt_regs *regs, long err)
}
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;