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Re: [Qemu-devel] [PATCH 07/11] kvm/x86: added hyper-v crash data and ctl


From: Denis V. Lunev
Subject: Re: [Qemu-devel] [PATCH 07/11] kvm/x86: added hyper-v crash data and ctl msr's get/set'ers
Date: Tue, 23 Jun 2015 12:47:53 +0300
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 23/06/15 02:52, Peter Hornyack wrote:
On Mon, Jun 22, 2015 at 9:05 AM, Denis V. Lunev <address@hidden> wrote:
From: Andrey Smetanin <address@hidden>

Added hyper-v crash msr's(HV_X64_MSR_CRASH*) data and control
geters and setters.

Signed-off-by: Andrey Smetanin <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Paolo Bonzini <address@hidden>
CC: Gleb Natapov <address@hidden>
---
  arch/x86/kvm/hyperv.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++
  arch/x86/kvm/x86.c    |  4 ++++
  2 files changed, 70 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f65fb622..0a7d373 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -46,6 +46,59 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
         return r;
  }

+static int kvm_hv_msr_get_crash_ctl(struct kvm_vcpu *vcpu, u64 *pdata)
+{
+       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
+
+       *pdata = hv->hv_crash_ctl;
I see that this is implemented so that userspace controls the Hyper-V
crash capabilities that are enabled - userspace must set
HV_X64_MSR_CRASH_CTL_NOTIFY before the guest reads
HV_X64_MSR_CRASH_CTL. I just want to check that you considered an
alternative: a simpler implementation would have the crash
capabilities statically defined by kvm, and
HV_X64_MSR_CRASH_CTL_CONTENTS could just be returned here (and
hv_crash_ctl could be removed from struct kvm_arch_hyperv).

The current implementation is potentially more flexible but makes the
MSR handling a little more awkward since the host_initiated bool needs
to be passed around (patch 09). I guess either approach seems ok to
me.

Also, if this patchset is used then it looks like
HV_X64_MSR_CRASH_CTL_CONTENTS can be removed.

Paolo,

do you have any opinion on this? I prefer
configurable way but there is no problem
to enable it by default dropping 'hv_panic'
property.

Regards,
    Den

+       return 0;
+}
+
+static int kvm_hv_msr_set_crash_ctl(struct kvm_vcpu *vcpu, u64 data)
+{
+       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
+
+       hv->hv_crash_ctl = data;
+       if ((data & HV_X64_MSR_CRASH_CTL_NOTIFY)) {
+               vcpu_debug(vcpu, "hv crash (0x%llx 0x%llx 0x%llx 0x%llx "
+                         "0x%llx)\n", hv->hv_crash_param[0],
+                         hv->hv_crash_param[1],
+                         hv->hv_crash_param[2],
+                         hv->hv_crash_param[3],
+                         hv->hv_crash_param[4]);
+
+               /* Send notification about crash to user space */
+               kvm_make_request(KVM_REQ_HV_CRASH, vcpu);
+               return 0;
Returning from here seems unnecessary - if more crash capabilities are
added in the future, the guest might want to invoke multiple
capabilities at once, so we'd want to check for those here too.

+       }
+
+       return 0;
+}
+
+static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
+                                    u32 index, u64 data)
+{
+       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
+
+       if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
+               return -EINVAL;
+
+       hv->hv_crash_param[index] = data;
+       return 0;
+}
+
+static int kvm_hv_msr_get_crash_data(struct kvm_vcpu *vcpu,
+                                    u32 index, u64 *pdata)
+{
+       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
+
+       if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
+               return -EINVAL;
+
+       *pdata = hv->hv_crash_param[index];
+       return 0;
+}
+
  static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
  {
         struct kvm *kvm = vcpu->kvm;
@@ -98,6 +152,12 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 
msr, u64 data)
                 mark_page_dirty(kvm, gfn);
                 break;
         }
+       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
+               return kvm_hv_msr_set_crash_data(vcpu,
+                                                msr - HV_X64_MSR_CRASH_P0,
+                                                data);
+       case HV_X64_MSR_CRASH_CTL:
+               return kvm_hv_msr_set_crash_ctl(vcpu, data);
         default:
                 vcpu_unimpl(vcpu, "Hyper-V unimpl wrmsr: 0x%x data 0x%llx\n",
                                   msr, data);
@@ -170,6 +230,12 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 
msr, u64 *pdata)
         case HV_X64_MSR_REFERENCE_TSC:
                 data = hv->hv_tsc_page;
                 break;
+       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
+               return kvm_hv_msr_get_crash_data(vcpu,
+                                                msr - HV_X64_MSR_CRASH_P0,
+                                                pdata);
+       case HV_X64_MSR_CRASH_CTL:
+               return kvm_hv_msr_get_crash_ctl(vcpu, pdata);
         default:
                 vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
                 return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2755c37..2046b78 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2208,6 +2208,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
                  */
                 break;
         case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
+       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
+       case HV_X64_MSR_CRASH_CTL:
                 return kvm_hv_set_msr_common(vcpu, msr, data);
                 break;
         case MSR_IA32_BBL_CR_CTL3:
@@ -2451,6 +2453,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, 
u64 *pdata)
                 data = 0x20000000;
                 break;
         case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
+       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
+       case HV_X64_MSR_CRASH_CTL:
                 return kvm_hv_get_msr_common(vcpu, msr, pdata);
                 break;
         case MSR_IA32_BBL_CR_CTL3:
--
1.9.1

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