From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>, Jon Kohler <jon@nutanix.com>,
Dave Hansen <dave.hansen@intel.com>,
Babu Moger <babu.moger@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Fenghua Yu <fenghua.yu@intel.com>,
Yu-cheng Yu <yu-cheng.yu@intel.com>,
Tony Luck <tony.luck@intel.com>, Uros Bizjak <ubizjak@gmail.com>,
Petteri Aimonen <jpa@git.mail.kapsi.fi>,
Kan Liang <kan.liang@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@kernel.org>,
Benjamin Thiel <b.thiel@posteo.de>,
Fan Yang <Fan_Yang@sjtu.edu.cn>, Juergen Gross <jgross@suse.com>,
Dave Jiang <dave.jiang@intel.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
LKML <linux-kernel@vger.kernel.org>,
kvm list <kvm@vger.kernel.org>
Subject: Re: [PATCH] KVM: x86: add hint to skip hidden rdpkru under kvm_load_host_xsave_state
Date: Mon, 17 May 2021 17:39:13 +0000 [thread overview]
Message-ID: <YKKqQZH7bX+7PDjX@google.com> (raw)
In-Reply-To: <5e01d18b-123c-b91f-c7b4-7ec583dd1ec6@redhat.com>
On Mon, May 17, 2021, Paolo Bonzini wrote:
> On 14/05/21 07:11, Andy Lutomirski wrote:
> > I don't even want to think about what happens if a perf NMI hits and
> > accesses host user memory while the guest PKRU is live (on VMX -- I
> > think this can't happen on SVM).
>
> This is indeed a problem, which indeed cannot happen on SVM but is there on
> VMX. Note that the function above is not handling all of the xstate, it's
> handling the *XSAVE state*, that is XCR0, XSS and PKRU. Thus the window is
> small, but it's there.
>
> Is it solvable at all, without having PKRU fields in the VMCS (and without
> masking NMIs in the LAPIC which would be too expensive)? Dave, Sean, what
> do you think?
The least awful solution would be to have the NMI handler restore the host's
PKRU. The NMI handler would need to save/restore the register, a la CR2, but the
whole thing could be optimized to run if and only if the NMI lands in the window
where the guest's PKRU is loaded.
next prev parent reply other threads:[~2021-05-17 17:39 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-07 16:44 [PATCH] KVM: x86: add hint to skip hidden rdpkru under kvm_load_host_xsave_state Jon Kohler
2021-05-07 16:52 ` Paolo Bonzini
2021-05-07 16:58 ` Dave Hansen
2021-05-07 17:13 ` Jon Kohler
2021-05-14 5:11 ` Andy Lutomirski
2021-05-17 2:50 ` Jon Kohler
2021-05-17 16:35 ` Tom Lendacky
2021-05-17 7:46 ` Paolo Bonzini
2021-05-17 17:39 ` Sean Christopherson [this message]
2021-05-17 17:55 ` Dave Hansen
2021-05-17 18:02 ` Sean Christopherson
[not found] ` <4e6f7056-6b66-46b9-9eac-922ae1c7b526@www.fastmail.com>
2021-05-17 17:59 ` Dave Hansen
2021-05-17 18:04 ` Sean Christopherson
2021-05-17 18:15 ` Jim Mattson
2021-05-17 18:34 ` Sean Christopherson
2021-05-19 22:44 ` Dave Hansen
2021-05-19 23:15 ` Andy Lutomirski
2021-05-17 13:54 ` Dave Hansen
2021-05-17 16:43 ` Paolo Bonzini
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