linux-kernel - Re: [PATCH v19 027/130] KVM: TDX: Define TDX architectural definitions

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Message-ID: <20240403163011.GD2444378@ls.amr.corp.intel.com>
Date: Wed, 3 Apr 2024 09:30:11 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: isaku.yamahata@...el.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
	Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
	Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
	Sean Christopherson <sean.j.christopherson@...el.com>,
	Xiaoyao Li <xiaoyao.li@...el.com>, isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 027/130] KVM: TDX: Define TDX architectural
 definitions

On Wed, Apr 03, 2024 at 08:04:03AM -0700,
Sean Christopherson <seanjc@...gle.com> wrote:

> On Mon, Feb 26, 2024, isaku.yamahata@...el.com wrote:
> > +union tdx_vcpu_state_details {
> > +	struct {
> > +		u64 vmxip	: 1;
> > +		u64 reserved	: 63;
> > +	};
> > +	u64 full;
> > +};
> 
> No unions please.  KVM uses unions in a few places where they are the lesser of
> all evils, but in general, unions are frowned upon.  Bitfields in particular are
> strongly discourage, as they are a nightmare to read/review and tend to generate
> bad code.
> 
> E.g. for this one, something like (names aren't great)
> 
> static inline bool tdx_has_pending_virtual_interrupt(struct kvm_vcpu *vcpu)
> {
> 	return <get "non arch field"> & TDX_VCPU_STATE_VMXIP;
> }


Sure, let me replace them with mask and shift.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>