linux-kernel - Re: [PATCH 0/2] KVM: xen: update shared_info when long

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Message-ID: <ZWoNzzYiZtloNQiv@google.com>
Date:   Fri, 1 Dec 2023 08:46:07 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paul Durrant <paul@....org>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] KVM: xen: update shared_info when long_mode is set

On Fri, Dec 01, 2023, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@...zon.com>
> 
> This series is based on my v9 of my "update shared_info and vcpu_info
> handling" series [1] and fixes an issue that was latent before the
> "allow shared_info to be mapped by fixed HVA" patch of that series allowed
> a VMM to set up shared_info before the VM booted and then leave it alone.

Uh, what?   If this is fixing an existing bug then it really shouldn't take a
dependency on a rather large and non-trivial series.  If the bug can only manifest
as a result of said series, then the fix absolutely belongs in that series.

This change from patch 1 in particular:

 -static int kvm_xen_shared_info_init(struct kvm *kvm, u64 addr, bool addr_is_gfn)
 +static int kvm_xen_shared_info_init(struct kvm *kvm)

practically screams for inclusion in that series which does:

 -static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 +static int kvm_xen_shared_info_init(struct kvm *kvm, u64 addr, bool addr_is_gfn)

Why not get the code right the first time instead of fixing it up in a completely
different series?