Re: [PATCH 1/2] kvm/x86: Hyper-V based guest crash data handling

[Andrey Smetanin <asmetanin@virtuozzo.com>]

On Wed, 2015-06-17 at 14:44 +0200, Paolo Bonzini wrote:
> 
> On 11/06/2015 15:18, Denis V. Lunev wrote:
> > From: Andrey Smetanin <asmetanin@virtuozzo.com>
> > 
> > Windows 2012 guests can notify hypervisor about occurred guest crash
> > (Windows bugcheck(BSOD)) by writing specific Hyper-V msrs. This patch does
> > handling of this MSR's by KVM and sending notification to user space that
> > allows to gather Windows guest crash dump by QEMU/LIBVIRT.
> > 
> > The idea is to provide functionality equal to pvpanic device without
> > QEMU guest agent for Windows.
> > 
> > The idea is borrowed from Linux HyperV bus driver and validated against
> > Windows 2k12.
> > 
> > Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> > Signed-off-by: Denis V. Lunev <den@openvz.org>
> > CC: Gleb Natapov <gleb@kernel.org>
> > CC: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  arch/x86/include/uapi/asm/hyperv.h | 10 +++++
> >  arch/x86/kvm/Makefile              |  2 +-
> >  arch/x86/kvm/mshv.c                | 84 ++++++++++++++++++++++++++++++++++++++
> >  arch/x86/kvm/mshv.h                | 32 +++++++++++++++
> 
> Please use hyperv.[ch] or hyper-v.[ch] and name the functions kvm_hv_*.
>  We can later move more functions from x86.c to the new file, so it's
> better to keep the names consistent.
> 
Should we prepare a 1st patch in this series where
we move all hyper-v related code from x86.c into hyperv.c new file with
copyright extension ?
> >  arch/x86/kvm/x86.c                 | 25 ++++++++++++
> >  include/linux/kvm_host.h           | 17 ++++++++
> >  include/uapi/linux/kvm.h           | 11 +++++
> >  7 files changed, 180 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/x86/kvm/mshv.c
> >  create mode 100644 arch/x86/kvm/mshv.h
> > 
> > diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> > index ce6068d..25f3064 100644
> > --- a/arch/x86/include/uapi/asm/hyperv.h
> > +++ b/arch/x86/include/uapi/asm/hyperv.h
> > @@ -199,6 +199,16 @@
> >  #define HV_X64_MSR_STIMER3_CONFIG		0x400000B6
> >  #define HV_X64_MSR_STIMER3_COUNT		0x400000B7
> >  
> > +
> > +/* Hypev-V guest crash notification MSR's */
> > +#define HV_X64_MSR_CRASH_P0			0x40000100
> > +#define HV_X64_MSR_CRASH_P1			0x40000101
> > +#define HV_X64_MSR_CRASH_P2			0x40000102
> > +#define HV_X64_MSR_CRASH_P3			0x40000103
> > +#define HV_X64_MSR_CRASH_P4			0x40000104
> > +#define HV_X64_MSR_CRASH_CTL			0x40000105
> > +#define HV_CRASH_CTL_CRASH_NOTIFY		(1ULL << 63)
> > +
> >  #define HV_X64_MSR_HYPERCALL_ENABLE		0x00000001
> >  #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT	12
> >  #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_MASK	\
> > diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
> > index 16e8f96..b1ec24d 100644
> > --- a/arch/x86/kvm/Makefile
> > +++ b/arch/x86/kvm/Makefile
> > @@ -12,7 +12,7 @@ kvm-y			+= $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o \
> >  kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(KVM)/async_pf.o
> >  
> >  kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
> > -			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o
> > +			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mshv.o
> >  kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)	+= assigned-dev.o iommu.o
> >  kvm-intel-y		+= vmx.o
> >  kvm-amd-y		+= svm.o
> > diff --git a/arch/x86/kvm/mshv.c b/arch/x86/kvm/mshv.c
> > new file mode 100644
> > index 0000000..ad367c44
> > --- /dev/null
> > +++ b/arch/x86/kvm/mshv.c
> > @@ -0,0 +1,84 @@
> > +/*
> > + * KVM Microsoft Hyper-V extended paravirtualization
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2.  See
> > + * the COPYING file in the top-level directory.
> > + *
> > + * Copyright (C) 2015 Andrey Smetanin <asmetanin@virtuozzo.com>
> > + *
> > + * Authors: Andrey Smetanin asmetanin@virtuozzo.com
> > + */
> > +
> > +#include <linux/kvm_host.h>
> > +#include "mshv.h"
> > +
> > +int kvm_mshv_ctx_create(struct kvm *kvm)
> > +{
> > +	struct kvm_mshv_ctx *ctx;
> > +
> > +	ctx = kzalloc(sizeof(struct kvm_mshv_ctx), GFP_KERNEL);
> > +	if (!ctx)
> > +		return -ENOMEM;
> > +
> > +	ctx->kvm = kvm;
> > +	atomic_set(&ctx->crash_pending, 0);
> > +	kvm->mshv_ctx = ctx;
> > +	return 0;
> > +}
> > +
> > +void kvm_mshv_ctx_destroy(struct kvm *kvm)
> > +{
> > +	kfree(kvm->mshv_ctx);
> > +}
> > +
> > +int kvm_mshv_msr_get_crash_ctl(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> > +{
> > +	struct kvm_mshv_ctx *ctx = kvm_vcpu_get_mshv_ctx(vcpu);
> > +
> > +	atomic_set(&ctx->crash_pending, 1);
> > +
> > +	/* Response that KVM ready to receive crash data */
> > +	*pdata = HV_CRASH_CTL_CRASH_NOTIFY;
> > +	return 0;
> > +}
> > +
> > +int kvm_mshv_msr_set_crash_ctl(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > +{
> > +	struct kvm_mshv_ctx *ctx = kvm_vcpu_get_mshv_ctx(vcpu);
> > +
> > +	if (atomic_dec_and_test(&ctx->crash_pending)) {
> > +		pr_debug("vcpu %p 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx",
> > +			 vcpu, ctx->crash_p0, ctx->crash_p1, ctx->crash_p2,
> > +			 ctx->crash_p3, ctx->crash_p4);
> > +
> > +		/* Crash data almost gathered so notify user space */
> 
> Why "almost" gathered?
> 
> > +		kvm_make_request(KVM_REQ_MSHV_CRASH, vcpu);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +int kvm_mshv_msr_set_crash_data(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > +{
> > +	struct kvm_mshv_ctx *ctx = kvm_vcpu_get_mshv_ctx(vcpu);
> > +
> > +	switch (msr) {
> > +	case HV_X64_MSR_CRASH_P0:
> > +		ctx->crash_p0 = data;
> > +		return 0;
> > +	case HV_X64_MSR_CRASH_P1:
> > +		ctx->crash_p1 = data;
> > +		return 0;
> > +	case HV_X64_MSR_CRASH_P2:
> > +		ctx->crash_p2 = data;
> > +		return 0;
> > +	case HV_X64_MSR_CRASH_P3:
> > +		ctx->crash_p3 = data;
> > +		return 0;
> > +	case HV_X64_MSR_CRASH_P4:
> > +		ctx->crash_p4 = data;
> > +		return 0;
> 
> Please use an array (with a WARN_ON_ONCE check that the index is in bounds).
> 
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > diff --git a/arch/x86/kvm/mshv.h b/arch/x86/kvm/mshv.h
> > new file mode 100644
> > index 0000000..ce8e7fa
> > --- /dev/null
> > +++ b/arch/x86/kvm/mshv.h
> > @@ -0,0 +1,32 @@
> > +/*
> > + * KVM Microsoft Hyper-V extended paravirtualization
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2.  See
> > + * the COPYING file in the top-level directory.
> > + *
> > + * Copyright (C) 2015 Andrey Smetanin <asmetanin@virtuozzo.com>
> > + *
> > + * Authors: Andrey Smetanin asmetanin@virtuozzo.com
> > + */
> > +
> > +#ifndef __ARCH_X86_KVM_MSHV_H__
> > +#define __ARCH_X86_KVM_MSHV_H__
> > +
> > +static inline struct kvm_mshv_ctx *kvm_get_mshv_ctx(struct kvm *vm)
> > +{
> > +	return vm->mshv_ctx;
> > +}
> > +
> > +static inline struct kvm_mshv_ctx *kvm_vcpu_get_mshv_ctx(struct kvm_vcpu *vcpu)
> > +{
> > +	return vcpu->kvm->mshv_ctx;
> > +}
> > +
> > +int kvm_mshv_msr_get_crash_ctl(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
> > +int kvm_mshv_msr_set_crash_ctl(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> > +int kvm_mshv_msr_set_crash_data(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> > +
> > +int kvm_mshv_ctx_create(struct kvm *kvm);
> > +void kvm_mshv_ctx_destroy(struct kvm *kvm);
> > +
> > +#endif
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index ea306ad..388b58f 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -28,6 +28,7 @@
> >  #include "x86.h"
> >  #include "cpuid.h"
> >  #include "assigned-dev.h"
> > +#include "mshv.h"
> >  
> >  #include <linux/clocksource.h>
> >  #include <linux/interrupt.h>
> > @@ -2338,6 +2339,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  		} else
> >  			return set_msr_hyperv(vcpu, msr, data);
> >  		break;
> > +	case HV_X64_MSR_CRASH_CTL:
> > +		return kvm_mshv_msr_set_crash_ctl(vcpu, msr, data);
> > +	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> > +		return kvm_mshv_msr_set_crash_data(vcpu, msr, data);
> >  	case MSR_IA32_BBL_CR_CTL3:
> >  		/* Drop writes to this legacy MSR -- see rdmsr
> >  		 * counterpart for further detail.
> > @@ -2650,6 +2655,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> >  		} else
> >  			return get_msr_hyperv(vcpu, msr, pdata);
> >  		break;
> > +	case HV_X64_MSR_CRASH_CTL:
> > +		return kvm_mshv_msr_get_crash_ctl(vcpu, msr, pdata);
> 
> Please implement get_crash_data as well.  Userspace may want to retrieve
> this value and stash it somewhere for post-mortem analysis, and
> KVM_GET_MSR is very handy for this purpose.
> 
> Do not return an error, just return the last written datum.
> 
> >  	case MSR_IA32_BBL_CR_CTL3:
> >  		/* This legacy MSR exists but isn't fully documented in current
> >  		 * silicon.  It is however accessed by winxp in very narrow
> > @@ -6280,6 +6287,20 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> >  			vcpu_scan_ioapic(vcpu);
> >  		if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))
> >  			kvm_vcpu_reload_apic_access_page(vcpu);
> > +		if (kvm_check_request(KVM_REQ_MSHV_CRASH, vcpu)) {
> > +			struct kvm_mshv_ctx *ctx = kvm_vcpu_get_mshv_ctx(vcpu);
> > +
> > +			vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
> > +			vcpu->run->system_event.type = KVM_SYSTEM_EVENT_CRASH;
> > +			vcpu->run->system_event.flags = 0;
> > +			vcpu->run->system_event.crash.p0 = ctx->crash_p0;
> > +			vcpu->run->system_event.crash.p1 = ctx->crash_p1;
> > +			vcpu->run->system_event.crash.p2 = ctx->crash_p2;
> > +			vcpu->run->system_event.crash.p3 = ctx->crash_p3;
> > +			vcpu->run->system_event.crash.p4 = ctx->crash_p4;
> > +			r = 0;
> > +			goto out;
> > +		}
> >  	}
> >  
> >  	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> > @@ -7418,6 +7439,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> >  	if (type)
> >  		return -EINVAL;
> >  
> > +	if (kvm_mshv_ctx_create(kvm))
> > +		return -ENOMEM;
> > +
> >  	INIT_HLIST_HEAD(&kvm->arch.mask_notifier_list);
> >  	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> >  	INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
> > @@ -7484,6 +7508,7 @@ void kvm_arch_sync_events(struct kvm *kvm)
> >  
> >  void kvm_arch_destroy_vm(struct kvm *kvm)
> >  {
> > +	kvm_mshv_ctx_destroy(kvm);
> >  	if (current->mm == kvm->mm) {
> >  		/*
> >  		 * Free memory regions allocated on behalf of userspace,
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index ad45054..83bd7bf 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -134,6 +134,7 @@ static inline bool is_error_page(struct page *page)
> >  #define KVM_REQ_ENABLE_IBS        23
> >  #define KVM_REQ_DISABLE_IBS       24
> >  #define KVM_REQ_APIC_PAGE_RELOAD  25
> > +#define KVM_REQ_MSHV_CRASH        26
> >  
> >  #define KVM_USERSPACE_IRQ_SOURCE_ID		0
> >  #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1
> > @@ -343,6 +344,21 @@ struct kvm_memslots {
> >  	int used_slots;
> >  };
> >  
> > +/*
> > + * Ms hyperv paravirt context
> > + */
> > +struct kvm_mshv_ctx {
> 
> This should be in an x86-specific file.  Please name it "struct
> kvm_arch_hyperv hv" and stick it inside struct kvm_arch (so it's
> accessed as kvm->arch.hv).  We can also move other fields, e.g.
> kvm->arch.hv_hypercall inside this new struct.
> 
> > +	struct kvm	*kvm;
> 
> Not needed if you avoid the pointer: then you can just use container_of.
> 
> > +	atomic_t	crash_pending;
> > +
> > +	/* Guest crash related parameters */
> > +	u64		crash_p0;
> > +	u64		crash_p1;
> > +	u64		crash_p2;
> > +	u64		crash_p3;
> > +	u64		crash_p4;
> > +};
> > +
> >  struct kvm {
> >  	spinlock_t mmu_lock;
> >  	struct mutex slots_lock;
> > @@ -395,6 +411,7 @@ struct kvm {
> >  #endif
> >  	long tlbs_dirty;
> >  	struct list_head devices;
> > +	struct kvm_mshv_ctx *mshv_ctx;
> >  };
> >  
> >  #define kvm_err(fmt, ...) \
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 4b60056..12f481b 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -317,8 +317,19 @@ struct kvm_run {
> >  		struct {
> >  #define KVM_SYSTEM_EVENT_SHUTDOWN       1
> >  #define KVM_SYSTEM_EVENT_RESET          2
> > +#define KVM_SYSTEM_EVENT_CRASH          3
> >  			__u32 type;
> >  			__u64 flags;
> > +			union {
> > +				struct {
> > +					/* Guest crash related parameters */
> > +					__u64 p0;
> > +					__u64 p1;
> > +					__u64 p2;
> > +					__u64 p3;
> > +					__u64 p4;
> > +				} crash;
> 
> No need to return the parameters here.  Userspace can use KVM_GET_MSR to
> read them.
> 
> Paolo
> 
> > +			};
> >  		} system_event;
> >  		/* KVM_EXIT_S390_STSI */
> >  		struct {
> >