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From: Jon Doron <arilou@gmail.com>
To: Roman Kagan <rvkagan@yandex-team.ru>,
	kvm@vger.kernel.org, linux-hyperv@vger.kernel.org,
	vkuznets@redhat.com
Subject: Re: [PATCH v11 6/7] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls
Date: Wed, 13 May 2020 15:39:26 +0300
Message-ID: <20200513123926.GL2862@jondnuc> (raw)
In-Reply-To: <20200512153353.GB9944@rvkaganb.lan>

On 12/05/2020, Roman Kagan wrote:
>On Fri, Apr 24, 2020 at 02:37:45PM +0300, Jon Doron wrote:
>> There is another mode for the synthetic debugger which uses hypercalls
>> to send/recv network data instead of the MSR interface.
>>
>> This interface is much slower and less recommended since you might get
>> a lot of VMExits while KDVM polling for new packets to recv, rather
>> than simply checking the pending page to see if there is data avialble
>> and then request.
>>
>> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Signed-off-by: Jon Doron <arilou@gmail.com>
>> ---
>>  arch/x86/kvm/hyperv.c | 28 ++++++++++++++++++++++++++++
>>  1 file changed, 28 insertions(+)
>>
>> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>> index 524b5466a515..744bcef88c70 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
>> @@ -1832,6 +1832,34 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>>  		}
>>  		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
>>  		break;
>> +	case HVCALL_POST_DEBUG_DATA:
>> +	case HVCALL_RETRIEVE_DEBUG_DATA:
>> +		if (unlikely(fast)) {
>> +			ret = HV_STATUS_INVALID_PARAMETER;
>> +			break;
>> +		}
>> +		fallthrough;
>> +	case HVCALL_RESET_DEBUG_SESSION: {
>> +		struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
>> +
>> +		if (!syndbg->active) {
>> +			ret = HV_STATUS_INVALID_HYPERCALL_CODE;
>> +			break;
>> +		}
>> +
>> +		if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
>> +			ret = HV_STATUS_OPERATION_DENIED;
>> +			break;
>> +		}
>> +		vcpu->run->exit_reason = KVM_EXIT_HYPERV;
>> +		vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
>> +		vcpu->run->hyperv.u.hcall.input = param;
>> +		vcpu->run->hyperv.u.hcall.params[0] = ingpa;
>> +		vcpu->run->hyperv.u.hcall.params[1] = outgpa;
>> +		vcpu->arch.complete_userspace_io =
>> +				kvm_hv_hypercall_complete_userspace;
>> +		return 0;
>> +	}
>
>I'd personally just push every hyperv hypercall not recognized by the
>kernel to userspace.  Smth like this:
>
>diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>index bcefa9d4e57e..f0404df0f488 100644
>--- a/arch/x86/kvm/hyperv.c
>+++ b/arch/x86/kvm/hyperv.c
>@@ -1644,6 +1644,48 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> 		}
> 		kvm_vcpu_on_spin(vcpu, true);
> 		break;
>+	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST:
>+		if (unlikely(fast || !rep_cnt || rep_idx)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
>+		break;
>+	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE:
>+		if (unlikely(fast || rep)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
>+		break;
>+	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
>+		if (unlikely(fast || !rep_cnt || rep_idx)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
>+		break;
>+	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
>+		if (unlikely(fast || rep)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
>+		break;
>+	case HVCALL_SEND_IPI:
>+		if (unlikely(rep)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, false, fast);
>+		break;
>+	case HVCALL_SEND_IPI_EX:
>+		if (unlikely(fast || rep)) {
>+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>+			break;
>+		}
>+		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
>+		break;
> 	case HVCALL_SIGNAL_EVENT:
> 		if (unlikely(rep)) {
> 			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>@@ -1653,12 +1695,8 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> 		if (ret != HV_STATUS_INVALID_PORT_ID)
> 			break;
> 		/* fall through - maybe userspace knows this conn_id. */
>-	case HVCALL_POST_MESSAGE:
>-		/* don't bother userspace if it has no way to handle it */
>-		if (unlikely(rep || !vcpu_to_synic(vcpu)->active)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>+	default:
>+		/* forward unrecognized hypercalls to userspace */
> 		vcpu->run->exit_reason = KVM_EXIT_HYPERV;
> 		vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
> 		vcpu->run->hyperv.u.hcall.input = param;
>@@ -1667,51 +1705,6 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> 		vcpu->arch.complete_userspace_io =
> 				kvm_hv_hypercall_complete_userspace;
> 		return 0;
>-	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST:
>-		if (unlikely(fast || !rep_cnt || rep_idx)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
>-		break;
>-	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE:
>-		if (unlikely(fast || rep)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
>-		break;
>-	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
>-		if (unlikely(fast || !rep_cnt || rep_idx)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
>-		break;
>-	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
>-		if (unlikely(fast || rep)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
>-		break;
>-	case HVCALL_SEND_IPI:
>-		if (unlikely(rep)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, false, fast);
>-		break;
>-	case HVCALL_SEND_IPI_EX:
>-		if (unlikely(fast || rep)) {
>-			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>-			break;
>-		}
>-		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
>-		break;
>-	default:
>-		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
>-		break;
> 	}
>
> 	return kvm_hv_hypercall_complete(vcpu, ret);
>
>(would also need a kvm cap for that)
>
>Roman.

This looks like a good idea, but I think it should be part of another 
patchset, I could revise one once this is in and expose a new CAP, and 
we need to make sure QEMU can handle this and wont just crash getting 
these additional exits.

-- Jon.

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-24 11:37 [PATCH v11 0/7] x86/kvm/hyper-v: add support for synthetic debugger Jon Doron
2020-04-24 11:37 ` [PATCH v11 1/7] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit Jon Doron
2020-05-13  8:42   ` Roman Kagan
2020-04-24 11:37 ` [PATCH v11 2/7] x86/kvm/hyper-v: Simplify addition for custom cpuid leafs Jon Doron
2020-05-13  9:24   ` Roman Kagan
2020-05-13 12:49     ` Jon Doron
2020-05-29 11:13       ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 3/7] x86/hyper-v: Add synthetic debugger definitions Jon Doron
2020-04-24 11:37 ` [PATCH v11 4/7] x86/kvm/hyper-v: Add support for synthetic debugger capability Jon Doron
2020-05-29 10:46   ` Paolo Bonzini
2020-05-29 12:08     ` Vitaly Kuznetsov
2020-05-29 12:17       ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 5/7] x86/kvm/hyper-v: enable hypercalls without hypercall page with syndbg Jon Doron
2020-05-13  9:57   ` Roman Kagan
2020-05-13 12:37     ` Jon Doron
2020-05-29 10:48   ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 6/7] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls Jon Doron
2020-05-12 15:33   ` Roman Kagan
2020-05-13 12:39     ` Jon Doron [this message]
2020-04-24 11:37 ` [PATCH v11 7/7] KVM: selftests: update hyperv_cpuid with SynDBG tests Jon Doron
2020-05-07  3:01 ` [PATCH v11 0/7] x86/kvm/hyper-v: add support for synthetic debugger Jon Doron
2020-05-07  7:57   ` Paolo Bonzini

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