From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Borislav Petkov <bp@suse.de>, Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, "Tom Lendacky" <thomas.lendacky@amd.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active
Date: Mon, 10 Sep 2018 09:13:23 -0700 [thread overview]
Message-ID: <1536596003.11460.82.camel@intel.com> (raw)
In-Reply-To: <20180910155329.GB20286@zn.tnic>
On Mon, 2018-09-10 at 17:53 +0200, Borislav Petkov wrote:
> On Mon, Sep 10, 2018 at 08:15:38AM -0500, Brijesh Singh wrote:
> >
> > >
> > > Now, the real question from all this SNAFU is, why can't all those point
> > > to a single struct pvclock_vsyscall_time_info and all CPUs read a single
> > > thing? Why do they have to be per-CPU and thus waste so much memory?
> You forgot to answer to the real question - why do we need those things
> to be perCPU and why can't we use a single instance to share with *all*
> CPUs?
I can't speak to the actual TSC stuff, but...
The pvclock ABI includes a per-vCPU bit, PVCLOCK_GUEST_STOPPED, to indicate
that the VM has been paused by the host. The guest uses this information to
update its watchdogs to avoid false positives. I have no idea if there are
use cases for setting STOPPED on a subset of vCPUs, but the ABI allows it so
here we are...
next prev parent reply other threads:[~2018-09-10 16:13 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 17:57 [PATCH v6 0/5] x86: Fix SEV guest regression Brijesh Singh
2018-09-07 17:57 ` [PATCH v6 1/5] x86/mm: Restructure sme_encrypt_kernel() Brijesh Singh
2018-09-10 11:32 ` Borislav Petkov
2018-09-07 17:57 ` [PATCH v6 2/5] x86/mm: fix sme_populate_pgd() to update page flags Brijesh Singh
2018-09-10 11:36 ` Borislav Petkov
2018-09-10 12:28 ` Brijesh Singh
2018-09-10 12:32 ` Borislav Petkov
2018-09-07 17:57 ` [PATCH v6 3/5] x86/mm: add .data..decrypted section to hold shared variables Brijesh Singh
2018-09-10 11:54 ` Borislav Petkov
2018-09-10 12:33 ` Brijesh Singh
2018-09-07 17:57 ` [PATCH v6 4/5] x86/kvm: use __decrypted attribute in " Brijesh Singh
2018-09-10 12:04 ` Borislav Petkov
2018-09-10 13:15 ` Sean Christopherson
2018-09-10 13:29 ` Thomas Gleixner
2018-09-10 15:34 ` Borislav Petkov
2018-09-10 12:29 ` Paolo Bonzini
2018-09-10 12:33 ` Borislav Petkov
2018-09-10 12:46 ` Paolo Bonzini
2018-09-07 17:57 ` [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active Brijesh Singh
2018-09-10 12:27 ` Borislav Petkov
2018-09-10 13:15 ` Brijesh Singh
2018-09-10 13:29 ` Sean Christopherson
2018-09-10 15:10 ` Brijesh Singh
2018-09-10 15:28 ` Sean Christopherson
2018-09-10 15:30 ` Brijesh Singh
2018-09-10 16:48 ` Borislav Petkov
2018-09-11 9:26 ` Paolo Bonzini
2018-09-11 10:01 ` Borislav Petkov
2018-09-11 10:19 ` Paolo Bonzini
2018-09-11 10:25 ` Borislav Petkov
2018-09-11 11:07 ` Paolo Bonzini
2018-09-11 13:55 ` Borislav Petkov
2018-09-11 14:00 ` Paolo Bonzini
2018-09-10 15:53 ` Borislav Petkov
2018-09-10 16:13 ` Sean Christopherson [this message]
2018-09-10 16:14 ` Brijesh Singh
2018-09-10 12:28 ` Paolo Bonzini
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