linux-kernel - Re: [PATCH v2 07/11] KVM: x86: emulator/smm: add structs for KVM's smram layout

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Date:   Thu, 21 Jul 2022 00:40:44 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v2 07/11] KVM: x86: emulator/smm: add structs for KVM's
 smram layout

On Tue, Jun 21, 2022, Maxim Levitsky wrote:
> Those structs will be used to read/write the smram state image.
> 
> Also document the differences between KVM's SMRAM layout and SMRAM
> layout that is used by real Intel/AMD cpus.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/kvm_emulate.h | 139 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 139 insertions(+)
> 
> diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
> index 89246446d6aa9d..7015728da36d5f 100644
> --- a/arch/x86/kvm/kvm_emulate.h
> +++ b/arch/x86/kvm/kvm_emulate.h
> @@ -503,6 +503,145 @@ enum x86_intercept {
>  	nr_x86_intercepts
>  };
>  
> +
> +/*
> + * 32 bit KVM's emulated SMM layout
> + * Loosely based on Intel's layout
> + */
> +
> +struct kvm_smm_seg_state_32 {
> +	u32 flags;
> +	u32 limit;
> +	u32 base;
> +} __packed;
> +
> +struct kvm_smram_state_32 {
> +
> +	u32 reserved1[62];			/* FE00 - FEF7 */
> +	u32 smbase;				/* FEF8 */
> +	u32 smm_revision;			/* FEFC */
> +	u32 reserved2[5];			/* FF00-FF13 */
> +	/* CR4 is not present in Intel/AMD SMRAM image*/
> +	u32 cr4;				/* FF14 */
> +	u32 reserved3[5];			/* FF18 */

Again, I love this approach, but we should have compile-time asserts to verify
the layout, e.g. see vmx_check_vmcs12_offsets().