linux-kernel - Re: [PATCH RESEND v4 23/23] KVM: x86: smm: preserve interrupt shadow in SMRAM

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Date:   Fri, 28 Oct 2022 12:35:15 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Yang Zhong <yang.zhong@...el.com>, x86@...nel.org,
        Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Shuah Khan <shuah@...nel.org>,
        Guang Zeng <guang.zeng@...el.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kselftest@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        "H. Peter Anvin" <hpa@...or.com>, Wei Wang <wei.w.wang@...el.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH RESEND v4 23/23] KVM: x86: smm: preserve interrupt shadow
 in SMRAM

On 10/25/22 14:47, Maxim Levitsky wrote:
> @@ -19,7 +19,8 @@ struct kvm_smram_state_32 {
>   	u32 reserved1[62];
>   	u32 smbase;
>   	u32 smm_revision;
> -	u32 reserved2[5];
> +	u32 reserved2[4];
> +	u32 int_shadow; /* KVM extension */
>   	u32 cr4; /* CR4 is not present in Intel/AMD SMRAM image */
>   	u32 reserved3[5];

Of course the placement of KVM-specific fields is somewhat arbitrary, 
but based on sandpile.org data I would place it at 0xFF1A ("reserved", 
you have to search for 7F1Ah in the web page).

> @@ -86,7 +87,7 @@ struct kvm_smram_state_64 {
>   	u64 io_restart_rsi;
>   	u64 io_restart_rdi;
>   	u32 io_restart_dword;
> -	u32 reserved1;
> +	u32 int_shadow;
>   	u8 io_inst_restart;
>   	u8 auto_hlt_restart;
>   	u8 reserved2[6];

Likewise, based on AMD BKDG I would place this at 0xFECB after the "NMI 
Mask" field (which unfortunately I learnt about only after "inventing" 
HF_SMM_INSIDE_NMI_MASK).

I can do the changes myself, but please ack.

Paolo