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SubjectRe: [PATCH 1/8] KVM: SVM: extract VMCB accessors to a new file
On 11/7/22 18:08, Sean Christopherson wrote:
> On Mon, Nov 07, 2022, Paolo Bonzini wrote:
>> Having inline functions confuses the compilation of asm-offsets.c,
>> which cannot find kvm_cache_regs.h because arch/x86/kvm is not in
>> asm-offset.c's include path. Just extract the functions to a
>> new file.
>>
>> No functional change intended.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly")
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> arch/x86/kvm/svm/avic.c | 1 +
>> arch/x86/kvm/svm/nested.c | 1 +
>> arch/x86/kvm/svm/sev.c | 1 +
>> arch/x86/kvm/svm/svm.c | 1 +
>> arch/x86/kvm/svm/svm.h | 200 ------------------------------
>> arch/x86/kvm/svm/svm_onhyperv.c | 1 +
>> arch/x86/kvm/svm/vmcb.h | 211 ++++++++++++++++++++++++++++++++
>
> I don't think vmcb.h is a good name. The logical inclusion sequence would be for
> svm.h to include vmcb.h, e.g. SVM requires knowledge about VMCBs, but this requires
> vmcb.h to include svm.h to dereference "struct vcpu_svm".
> Unlike VMX's vmcs.h, the new file isn't a "pure" VMCB helper, it also holds a
> decent amount of KVM's SVM logic.

Yes, it's basically the wrappers that KVM uses to access the VMCB fields.

> What about making KVM self-sufficient?

You mean having a different asm-offsets.h file just for arch/x86/kvm/?

> The includes in asm-offsets.c are quite ugly
>
> #include "../kvm/vmx/vmx.h"
> #include "../kvm/svm/svm.h"
>
> or as a stopgap to make backporting easier, just include kvm_cache_regs.h?

The problem is that the _existing_ include of kvm_cache_regs.h in svm.h
fails, with

arch/x86/kernel/../kvm/svm/svm.h:25:10: fatal error: kvm_cache_regs.h:
No such file or directory
25 | #include "kvm_cache_regs.h"
| ^~~~~~~~~~~~~~~~~~
compilation terminated.

The other two solutions here are:

1) move kvm_cache_regs.h to arch/x86/include/asm/ so it can be included
normally

2) extract the structs to arch/x86/kvm/svm/svm_types.h and include that
from asm-offsets.h, basically the opposite of this patch.

(2) is my preference if having a different asm-offsets.h file turns out
to be too complex. We can do the same for VMX as well.

Paolo

>> void svm_leave_nested(struct kvm_vcpu *vcpu);
>> diff --git a/arch/x86/kvm/svm/svm_onhyperv.c b/arch/x86/kvm/svm/svm_onhyperv.c
>> index 8cdc62c74a96..ae0a101329e6 100644
>> --- a/arch/x86/kvm/svm/svm_onhyperv.c
>> +++ b/arch/x86/kvm/svm/svm_onhyperv.c
>> @@ -8,6 +8,7 @@
>> #include <asm/mshyperv.h>
>>
>> #include "svm.h"
>> +#include "vmcb.h"
>> #include "svm_ops.h"
>>
>> #include "hyperv.h"
>> diff --git a/arch/x86/kvm/svm/vmcb.h b/arch/x86/kvm/svm/vmcb.h
>> new file mode 100644
>> index 000000000000..8757cda27e3a
>> --- /dev/null
>> +++ b/arch/x86/kvm/svm/vmcb.h
>> @@ -0,0 +1,211 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Kernel-based Virtual Machine driver for Linux
>> + *
>> + * AMD SVM support - VMCB accessors
>> + */
>> +
>> +#ifndef __SVM_VMCB_H
>> +#define __SVM_VMCB_H
>> +
>> +#include "kvm_cache_regs.h"
> This should include "svm.h" instead of relying on the parent to include said file.
>

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