linux-kernel - Re: [PATCH] KVM: x86: don't expose syscall/sysret to intel 32-bit guest

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Message-ID: <CANRm+CxoipUJEzx0MBMbG84GLmf_f+3fSs1YOPTwme2dwZ7UDA@mail.gmail.com>
Date:	Wed, 25 Nov 2015 20:45:28 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Wanpeng li <wanpeng.li@...mail.com>, kvm <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: don't expose syscall/sysret to intel 32-bit guest

2015-11-19 19:05 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>
> 1) Clear F(SYSCALL) in kvm_update_cpuid, like you are doing here but
> only if F(LM) is already clear (in addition to the vendor being Intel).

It seems that F(LM) is always set in the case of qemu-system-x86_64 w/
32-bit guest, vmware also exposes LM bit to 32 bit guest(however it
doesn't expose syscall/sysret), so maybe we can't depend on F(LM).

Regards,
Wanpeng Li
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