linux-kernel - RE: [PATCH v1 6/6] x86/hyperv: Enable build of hypervisor crashdump collection files

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Message-ID:
 <SN6PR02MB41575C12515CFF532B8B51C8D416A@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Thu, 18 Sep 2025 23:53:21 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Mukesh R <mrathor@...ux.microsoft.com>, "linux-hyperv@...r.kernel.org"
	<linux-hyperv@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org"
	<linux-arch@...r.kernel.org>
CC: "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
	<haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"decui@...rosoft.com" <decui@...rosoft.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de"
	<bp@...en8.de>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
	"arnd@...db.de" <arnd@...db.de>
Subject: RE: [PATCH v1 6/6] x86/hyperv: Enable build of hypervisor crashdump
 collection files

From: Mukesh R <mrathor@...ux.microsoft.com> Sent: Tuesday, September 16, 2025 6:16 PM
> 
> On 9/15/25 10:56, Michael Kelley wrote:
> > From: Mukesh Rathor <mrathor@...ux.microsoft.com> Sent: Tuesday, September 9, 2025 5:10 PM
> >>
> >> Enable build of the new files introduced in the earlier commits and add
> >> call to do the setup during boot.
> >>
> >> Signed-off-by: Mukesh Rathor <mrathor@...ux.microsoft.com>
> >> ---
> >>  arch/x86/hyperv/Makefile       | 6 ++++++
> >>  arch/x86/hyperv/hv_init.c      | 1 +
> >>  include/asm-generic/mshyperv.h | 9 +++++++++
> >>  3 files changed, 16 insertions(+)
> >>
> >> diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
> >> index d55f494f471d..6f5d97cddd80 100644
> >> --- a/arch/x86/hyperv/Makefile
> >> +++ b/arch/x86/hyperv/Makefile
> >> @@ -5,4 +5,10 @@ obj-$(CONFIG_HYPERV_VTL_MODE)	+= hv_vtl.o
> >>
> >>  ifdef CONFIG_X86_64
> >>  obj-$(CONFIG_PARAVIRT_SPINLOCKS)	+= hv_spinlock.o
> >> +
> >> + ifdef CONFIG_MSHV_ROOT
> >> +  CFLAGS_REMOVE_hv_trampoline.o += -pg
> >> +  CFLAGS_hv_trampoline.o        += -fno-stack-protector
> >> +  obj-$(CONFIG_CRASH_DUMP)      += hv_crash.o hv_trampoline.o
> >> + endif
> >>  endif
> >> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> >> index afdbda2dd7b7..577bbd143527 100644
> >> --- a/arch/x86/hyperv/hv_init.c
> >> +++ b/arch/x86/hyperv/hv_init.c
> >> @@ -510,6 +510,7 @@ void __init hyperv_init(void)
> >>  		memunmap(src);
> >>
> >>  		hv_remap_tsc_clocksource();
> >> +		hv_root_crash_init();
> >>  	} else {
> >>  		hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
> >>  		wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> >> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> >> index dbd4c2f3aee3..952c221765f5 100644
> >> --- a/include/asm-generic/mshyperv.h
> >> +++ b/include/asm-generic/mshyperv.h
> >> @@ -367,6 +367,15 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32
> >> num_pages);
> >>  int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
> >>  int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
> >>
> >> +#if CONFIG_CRASH_DUMP
> >> +void hv_root_crash_init(void);
> >> +void hv_crash_asm32(void);
> >> +void hv_crash_asm64_lbl(void);
> >> +void hv_crash_asm_end(void);
> >> +#else   /* CONFIG_CRASH_DUMP */
> >> +static inline void hv_root_crash_init(void) {}
> >> +#endif  /* CONFIG_CRASH_DUMP */
> >> +
> >
> > The hv_crash_asm* functions are x86 specific. Seems like their
> > declarations should go in arch/x86/include/asm/mshyperv.h, not in
> > the architecture-neutral include/asm-generic/mshyperv.h.
> 
> well, arm port is going on. i suppose i could move it to x86 and
> they can move it back  here in their patch submissions. hopefully
> they will remember or someone will catch it.

I could see the ARM64 implementation implementing its own version
of hv_root_crash_init() since that's a generic name. But sharing the
"asm" function names across architectures seems more questionable.
I doubt there would be hv_crash_asm32() on ARM64. :-)

> 
> >>  #else /* CONFIG_MSHV_ROOT */
> >>  static inline bool hv_root_partition(void) { return false; }
> >>  static inline bool hv_l1vh_partition(void) { return false; }
> >> --
> >> 2.36.1.vfs.0.0
> >>