linux-kernel - Re: [PATCH v3 7/8] KVM:X86: Add XSS bit 11 and 12 support for CET xsaves/xrstors.

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Date:   Fri, 8 Mar 2019 11:49:17 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yang Weijiang <weijiang.yang@...el.com>, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, jmattson@...gle.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org, mst@...hat.com,
        yu-cheng.yu@...el.com
Cc:     Zhang Yi Z <yi.z.zhang@...ux.intel.com>,
        Luwei Kang <luwei.kang@...el.com>
Subject: Re: [PATCH v3 7/8] KVM:X86: Add XSS bit 11 and 12 support for CET
 xsaves/xrstors.

On 25/02/19 14:27, Yang Weijiang wrote:
> For Guest XSS, right now, only bit 11(user states) and bit 12
> (supervisor states) are supported, if other bits are being set,
> need to modify KVM_SUPPORTED_XSS macro to have support.
> 
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
>  arch/x86/kvm/vmx.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index d32cee9ee079..68908ed7b151 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -47,6 +47,7 @@
>  #include <asm/virtext.h>
>  #include <asm/mce.h>
>  #include <asm/fpu/internal.h>
> +#include <asm/fpu/types.h>
>  #include <asm/perf_event.h>
>  #include <asm/debugreg.h>
>  #include <asm/kexec.h>
> @@ -4336,12 +4337,13 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	case MSR_IA32_XSS:
>  		if (!vmx_xsaves_supported())
>  			return 1;
> +
>  		/*
> -		 * The only supported bit as of Skylake is bit 8, but
> -		 * it is not supported on KVM.
> +		 * Check bits being set are supported in KVM.
>  		 */
> -		if (data != 0)
> +		if (data & ~kvm_supported_xss())
>  			return 1;
> +
>  		vcpu->arch.ia32_xss = data;
>  		if (vcpu->arch.ia32_xss != host_xss)
>  			add_atomic_switch_msr(vmx, MSR_IA32_XSS,
> 

Luwei, can you work with Weijiang to add XSAVES support for Processor
Tracing?

Paolo