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From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@suse.de>
Cc: "Brijesh Singh" <brijesh.singh@amd.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	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>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active
Date: Tue, 11 Sep 2018 13:07:06 +0200	[thread overview]
Message-ID: <cacb6865-e4ad-80c9-7482-23e480a61b0f@redhat.com> (raw)
In-Reply-To: <20180911102504.GC11418@zn.tnic>

On 11/09/2018 12:25, Borislav Petkov wrote:
> On Tue, Sep 11, 2018 at 12:19:13PM +0200, Paolo Bonzini wrote:
>> That's exactly what kvmclock is for, it provides a stable and
>> synchronized clock on top of unsynchronized TSCs.  But that's also why
>> you need one struct per vCPU, at least in the synchronized case.
                                                 ^^^^^^^^^^^^

unsynchronized

> 
> Why?
> 
> Why can't it be a single pointer to a struct pvclock_vsyscall_time_info
> shared between all vCPUs?
> 
> Or does each vCPU write its own specific stuff into it so it has to be
> per-vCPU?

If the host TSCs are unsynchronized then yes, that's what happens.  And
you can do live migration from synchronized to unsynchronized.

Paolo

  reply	other threads:[~2018-09-11 11:07 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 [this message]
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
2018-09-10 16:14         ` Brijesh Singh
2018-09-10 12:28   ` Paolo Bonzini

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