linux-kernel - Re: [PATCH v3 07/13] KVM: x86: emulator/smm: add structs for KVM's smram layout

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Date:   Wed, 24 Aug 2022 22:06:01 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Jim Mattson <jmattson@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v3 07/13] KVM: x86: emulator/smm: add structs for KVM's
 smram layout

On Wed, Aug 03, 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/emulate.c     |   6 +
>  arch/x86/kvm/kvm_emulate.h | 218 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c         |   1 +
>  3 files changed, 225 insertions(+)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 18551611cb13af..55d9328e6074a2 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -5864,3 +5864,9 @@ bool emulator_can_use_gpa(struct x86_emulate_ctxt *ctxt)
>  
>  	return true;
>  }
> +
> +void  __init kvm_emulator_init(void)
> +{
> +	__check_smram32_offsets();
> +	__check_smram64_offsets();
> +}

...

> +static inline void __check_smram64_offsets(void)

Why double underscores?  Same question for the macros.

> +{
> +#define __CHECK_SMRAM64_OFFSET(field, offset) \
> +	ASSERT_STRUCT_OFFSET(struct kvm_smram_state_64, field, offset - 0xFE00)
> +
> +	__CHECK_SMRAM64_OFFSET(es,			0xFE00);
> +	__CHECK_SMRAM64_OFFSET(cs,			0xFE10);
> +	__CHECK_SMRAM64_OFFSET(ss,			0xFE20);
> +	__CHECK_SMRAM64_OFFSET(ds,			0xFE30);
> +	__CHECK_SMRAM64_OFFSET(fs,			0xFE40);
> +	__CHECK_SMRAM64_OFFSET(gs,			0xFE50);
> +	__CHECK_SMRAM64_OFFSET(gdtr,			0xFE60);
> +	__CHECK_SMRAM64_OFFSET(ldtr,			0xFE70);
> +	__CHECK_SMRAM64_OFFSET(idtr,			0xFE80);
> +	__CHECK_SMRAM64_OFFSET(tr,			0xFE90);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rip,		0xFEA0);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rcx,		0xFEA8);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rsi,		0xFEB0);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rdi,		0xFEB8);
> +	__CHECK_SMRAM64_OFFSET(io_restart_dword,	0xFEC0);
> +	__CHECK_SMRAM64_OFFSET(reserved1,		0xFEC4);
> +	__CHECK_SMRAM64_OFFSET(io_inst_restart,		0xFEC8);
> +	__CHECK_SMRAM64_OFFSET(auto_hlt_restart,	0xFEC9);
> +	__CHECK_SMRAM64_OFFSET(reserved2,		0xFECA);
> +	__CHECK_SMRAM64_OFFSET(efer,			0xFED0);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_flag,		0xFED8);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_vmcb_gpa,	0xFEE0);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_virtual_int,	0xFEE8);
> +	__CHECK_SMRAM64_OFFSET(reserved3,		0xFEF0);
> +	__CHECK_SMRAM64_OFFSET(smm_revison,		0xFEFC);
> +	__CHECK_SMRAM64_OFFSET(smbase,			0xFF00);
> +	__CHECK_SMRAM64_OFFSET(reserved4,		0xFF04);
> +	__CHECK_SMRAM64_OFFSET(ssp,			0xFF18);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_pat,		0xFF20);
> +	__CHECK_SMRAM64_OFFSET(svm_host_efer,		0xFF28);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr4,		0xFF30);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr3,		0xFF38);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr0,		0xFF40);
> +	__CHECK_SMRAM64_OFFSET(cr4,			0xFF48);
> +	__CHECK_SMRAM64_OFFSET(cr3,			0xFF50);
> +	__CHECK_SMRAM64_OFFSET(cr0,			0xFF58);
> +	__CHECK_SMRAM64_OFFSET(dr7,			0xFF60);
> +	__CHECK_SMRAM64_OFFSET(dr6,			0xFF68);
> +	__CHECK_SMRAM64_OFFSET(rflags,			0xFF70);
> +	__CHECK_SMRAM64_OFFSET(rip,			0xFF78);
> +	__CHECK_SMRAM64_OFFSET(gprs,			0xFF80);
> +#undef __CHECK_SMRAM64_OFFSET
> +}
> +
> +union kvm_smram {
> +	struct kvm_smram_state_64 smram64;
> +	struct kvm_smram_state_32 smram32;
> +	u8 bytes[512];
> +};
> +
> +void  __init kvm_emulator_init(void);
> +
> +

Unnecessary newline.

>  /* Host execution mode. */
>  #if defined(CONFIG_X86_32)
>  #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 33560bfa0cac6e..bea7e5015d592e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -13355,6 +13355,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_msr_protocol_exit);
>  static int __init kvm_x86_init(void)
>  {
>  	kvm_mmu_x86_module_init();
> +	kvm_emulator_init();

Please don't add an init call that is nop at runtime, e.g. I was _really_ curious
what initialization needed to be done in the emulator.  And it makes it look like
kvm_x86_exit() forgot to call kvm_emulator_exit().

em_rsm() already ends up with

	BUILD_BUG_ON(sizeof(smram) != 512);

just put all the assertions there.

>  	return 0;
>  }
>  module_init(kvm_x86_init);
> -- 
> 2.26.3
>