linux-kernel - Re: [PATCH v1 1/8] kvm:vmx Introduce CET related VMCS field definitions.

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Date:   Wed, 2 Jan 2019 10:09:39 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org, mst@...hat.com,
        yu-cheng.yu@...el.com, yi.z.zhang@...el.com, hjl.tools@...il.com,
        Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v1 1/8] kvm:vmx  Introduce CET related VMCS field
 definitions.

On Wed, Dec 26, 2018 at 04:15:25PM +0800, Yang Weijiang wrote:
> VMX relies on these fields to save/restore CET states for
> guest and host. They are added here as VMCS placeholders
> for the function.

The changelog needs a lot more detail on what is saved where and when,
e.g. hardware unconditionally saves the guest MSRs to the VMCS fields
on exit, hence there is no VM_EXIT_SAVE_GUEST_CET_STATE control bit.

It's also worth calling out that the other CET MSRs are saved/loaded
via XSAVES/XRSTORS.

> 
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
>  arch/x86/include/asm/vmx.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index ade0f153947d..db745a1d49ae 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -98,6 +98,7 @@
>  #define VM_EXIT_LOAD_IA32_EFER                  0x00200000
>  #define VM_EXIT_SAVE_VMX_PREEMPTION_TIMER       0x00400000
>  #define VM_EXIT_CLEAR_BNDCFGS                   0x00800000
> +#define VM_EXIT_LOAD_HOST_CET_STATE             0x10000000
>  
>  #define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR	0x00036dff
>  
> @@ -109,6 +110,7 @@
>  #define VM_ENTRY_LOAD_IA32_PAT			0x00004000
>  #define VM_ENTRY_LOAD_IA32_EFER                 0x00008000
>  #define VM_ENTRY_LOAD_BNDCFGS                   0x00010000
> +#define VM_ENTRY_LOAD_GUEST_CET_STATE           0x00100000
>  
>  #define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR	0x000011ff
>  
> @@ -325,6 +327,9 @@ enum vmcs_field {
>  	GUEST_PENDING_DBG_EXCEPTIONS    = 0x00006822,
>  	GUEST_SYSENTER_ESP              = 0x00006824,
>  	GUEST_SYSENTER_EIP              = 0x00006826,
> +	GUEST_IA32_S_CET                = 0x00006828,
> +	GUEST_SSP                       = 0x0000682a,
> +	GUEST_INT_SSP_TABL              = 0x0000682c,

Dropping a single letter from "TABLE" seems pointless, "INTERRUPT" is
usually "INTR", and the docs I've seen list the name as
IA32_INTERRUPT_SSP_TABLE_ADDR.  So maybe?

    {GUEST,HOST}_INTR_SSP_TABLE_ADDR


Also, the SSP and INTERRUPT_SSP_TABL_ADDR fields are 64-bit fields, we
we should define the _HIGH variations.


>  	HOST_CR0                        = 0x00006c00,
>  	HOST_CR3                        = 0x00006c02,
>  	HOST_CR4                        = 0x00006c04,
> @@ -337,6 +342,9 @@ enum vmcs_field {
>  	HOST_IA32_SYSENTER_EIP          = 0x00006c12,
>  	HOST_RSP                        = 0x00006c14,
>  	HOST_RIP                        = 0x00006c16,
> +	HOST_IA32_S_CET                 = 0x00006c18,
> +	HOST_SSP                        = 0x00006c1a,
> +	HOST_INT_SSP_TABL               = 0x00006c1c
>  };
>  
>  /*
> -- 
> 2.17.1
>