linux-kernel - Re: [PATCH v14 011/113] KVM: TDX: Add C wrapper functions for SEAMCALLs to the TDX module

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Date:   Wed, 7 Jun 2023 11:15:37 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>
Cc:     "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>,
        "Chen, Bo2" <chen.bo@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v14 011/113] KVM: TDX: Add C wrapper functions for
 SEAMCALLs to the TDX module

On Mon, Jun 05, 2023 at 03:20:19PM +0000,
"Wang, Wei W" <wei.w.wang@...el.com> wrote:

> > diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
> > new file mode 100644 index 000000000000..893cc6c25f3b
> > --- /dev/null
> > +++ b/arch/x86/kvm/vmx/tdx_ops.h
> > @@ -0,0 +1,202 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* constants/data definitions for TDX SEAMCALLs */
> > +
> > +#ifndef __KVM_X86_TDX_OPS_H
> > +#define __KVM_X86_TDX_OPS_H
> > +
> > +#include <linux/compiler.h>
> > +
> > +#include <asm/cacheflush.h>
> > +#include <asm/asm.h>
> > +#include <asm/kvm_host.h>
> > +
> > +#include "tdx_errno.h"
> > +#include "tdx_arch.h"
> > +#include "x86.h"
> > +
> > +static inline u64 kvm_seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> > +			       struct tdx_module_output *out) {
> > +	u64 ret;
> > +
> > +	ret = __seamcall(op, rcx, rdx, r8, r9, out);
> > +	if (unlikely(ret == TDX_SEAMCALL_UD)) {
> > +		/*
> > +		 * TDX requires VMXON or #UD.  In the case of reboot or
> > kexec,
> > +		 * VMX is made off (VMXOFF) by kvm reboot notifier,
> > +		 * kvm_reboot(), while TDs are still running.  The callers
> > check
> > +		 * the returned error and complain.  Suppress it by returning 0.
> > +		 */
> 
> Curious how do the callers check the returned error when " Suppress
> it by returning 0" here.

It doesn't make sense for the caller to check the error and warn when
kvm_rebooting = true.
Let's make it "return kvm_rebooting ? 0 : ret;" instread of "return 0;".
Does it make sense?
-- 
Isaku Yamahata <isaku.yamahata@...il.com>