From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Chang Seok Bae <chang.seok.bae@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Sasha Levin <sashal@kernel.org>, kvm list <kvm@vger.kernel.org>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled
Date: Wed, 16 Sep 2020 18:54:57 +0200 [thread overview]
Message-ID: <de679a1f-8a6d-6db2-d891-6069ed4cb33e@redhat.com> (raw)
In-Reply-To: <CALCETrXn5DHzySo3JGfAn=Ckhn4UG48L-UjauG8_L0D9Sd=WXg@mail.gmail.com>
On 22/08/20 18:42, Andy Lutomirski wrote:
> On VMX, when a VM exits, the VM's
> value of MSR_TSC_AUX is live, and we can take an NMI, MCE, or
> abominable new #SX, #VE, #VC, etc on the next instruction boundary.
> And unless we use the atomic MSR switch mechanism, the result is that
> we're going through the entry path with guest-controlled MSRs.
If anything of that is a problem, we can and will use the atomic MSR
switching; it's not worth doing complicated stuff if you're going to pay
the price of rdmsr/wrmsr anyway.
The remaining cases are MSRs that are really meant for usermode (such as
the syscall MSRs) and especially the edge cases of these two MSRs that
the kernel doesn't mind too much about. But they are really really
rare, I don't expect any new one coming soon and if they are ever needed
(by SGX perhaps?!?) I'll certainly loop you guys in.
Paolo
next prev parent reply other threads:[~2020-09-16 20:51 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 2:50 Sean Christopherson
2020-08-21 7:24 ` peterz
2020-08-21 7:44 ` Borislav Petkov
2020-08-21 7:47 ` Borislav Petkov
2020-08-21 8:09 ` Paolo Bonzini
2020-08-21 8:16 ` Borislav Petkov
2020-08-21 9:05 ` Paolo Bonzini
2020-08-21 9:22 ` Borislav Petkov
2020-08-21 9:44 ` Paolo Bonzini
2020-08-21 9:48 ` Borislav Petkov
2020-08-21 10:07 ` Paolo Bonzini
2020-08-22 16:42 ` Andy Lutomirski
2020-09-16 16:54 ` Paolo Bonzini [this message]
2020-08-21 9:28 ` Thomas Gleixner
2020-08-21 9:37 ` Paolo Bonzini
2020-08-21 19:55 ` hpa
2020-08-21 20:02 ` Peter Zijlstra
2020-08-21 8:56 ` kernel test robot
2020-08-21 10:28 ` kernel test robot
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