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From: Thomas Gleixner <tglx@linutronix.de>
To: Sean Christopherson <seanjc@google.com>,
	Andrei Vagin <avagin@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Wanpeng Li <wanpengli@tencent.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Jianfeng Tan <henry.tjf@antfin.com>,
	Adin Scannell <ascannell@google.com>,
	Konstantin Bogomolov <bogomolov@google.com>,
	Etienne Perot <eperot@google.com>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 0/5] KVM/x86: add a new hypercall to execute host system
Date: Wed, 27 Jul 2022 00:10:12 +0200	[thread overview]
Message-ID: <875yjjttiz.ffs@tglx> (raw)
In-Reply-To: <YuAD6qY+F2nuGm62@google.com>

On Tue, Jul 26 2022 at 15:10, Sean Christopherson wrote:
> On Tue, Jul 26, 2022, Andrei Vagin wrote:
>> * It doesn't allow to support Confidential Computing (SEV-ES/SGX). The Sentry
>>   has to be fully enclosed in a VM to be able to support these technologies.
>
> Speaking of SGX, this reminds me a lot of Graphene, SCONEs, etc..., which IIRC
> tackled the "syscalls are crazy expensive" problem by using a message queue and
> a dedicated task outside of the enclave to handle syscalls.  Would something like
> that work, or is having to burn a pCPU (or more) to handle syscalls in the host a
> non-starter?

Let's put VMs aside for a moment. The problem you are trying to solve is
ptrace overhead because that requires context switching, right?

Did you ever try to solve this with SYSCALL_USER_DISPATCH? That requires
signals, which are not cheap either, but we certainly could come up with
a lightweight signal implementation for that particular use case.

Thanks,

        tglx


  reply	other threads:[~2022-07-26 22:10 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-22 23:02 [PATCH 0/5] KVM/x86: add a new hypercall to execute host system Andrei Vagin
2022-07-22 23:02 ` [PATCH 1/5] kernel: add a new helper to execute system calls from kernel code Andrei Vagin
2022-07-22 23:02 ` [PATCH 2/5] kvm/x86: add controls to enable/disable paravirtualized system calls Andrei Vagin
2022-07-22 23:02 ` [PATCH 3/5] KVM/x86: add a new hypercall to execute host " Andrei Vagin
2022-07-22 23:02 ` [PATCH 4/5] selftests/kvm/x86_64: set rax before vmcall Andrei Vagin
2022-08-01 11:32   ` Vitaly Kuznetsov
2022-08-01 12:43     ` Paolo Bonzini
2022-07-22 23:02 ` [PATCH 5/5] selftests/kvm/x86_64: add tests for KVM_HC_HOST_SYSCALL Andrei Vagin
2022-07-22 23:41 ` [PATCH 0/5] KVM/x86: add a new hypercall to execute host system Sean Christopherson
2022-07-26  8:33   ` Andrei Vagin
2022-07-26 10:27     ` Paolo Bonzini
2022-07-27  6:44       ` Andrei Vagin
2022-07-26 15:10     ` Sean Christopherson
2022-07-26 22:10       ` Thomas Gleixner [this message]
2022-07-27  1:03         ` Andrei Vagin
2022-08-22 20:26           ` Andrei Vagin
2022-07-27  0:25       ` Andrei Vagin
2022-07-26 21:27   ` Thomas Gleixner

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