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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Radim Krcmar <rkrcmar@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juergen Gross <jgross@suse.com>,
	Pavel Tatashin <pasha.tatashin@oracle.com>,
	steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
	x86@kernel.org, kvm@vger.kernel.org
Subject: [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups
Date: Fri, 06 Jul 2018 18:13:07 +0200	[thread overview]
Message-ID: <20180706161307.733337643@linutronix.de> (raw)

To allow early utilization of kvmclock it is required to remove the
memblock dependency. memblock is currently used to allocate the per
cpu data for kvmclock.

The first patch replaces the memblock with a static array sized 64bytes *
NR_CPUS and was posted by Pavel. That patch allocates everything statically
which is a waste when kvmclock is not used.

The rest of the series cleans up the code and converts it to per cpu
variables but does not put the kvmclock data into the per cpu area as that
has an issue vs. mapping the boot cpu data into the VDSO (leaks arbitrary
data, unless page sized).

The per cpu data consists of pointers to the actual data. For the boot cpu
a page sized array is statically allocated which can be mapped into the
VDSO. That array is used for initializing the first 64 CPU pointers. If
there are more CPUs the pvclock data is allocated during CPU bringup.

So this still will have some overhead when kvmclock is not in use, but
bringing it down to zero would be a massive trainwreck and even more
indirections.

Thanks,

	tglx

8<--------------
 a/arch/x86/include/asm/kvm_guest.h |    7 
 arch/x86/include/asm/kvm_para.h    |    1 
 arch/x86/kernel/kvm.c              |   14 -
 arch/x86/kernel/kvmclock.c         |  262 ++++++++++++++-----------------------
 arch/x86/kernel/setup.c            |    4 
 5 files changed, 105 insertions(+), 183 deletions(-)





             reply	other threads:[~2018-07-06 16:23 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-06 16:13 Thomas Gleixner [this message]
2018-07-06 16:13 ` [patch 1/7] x86/kvmclock: Remove memblock dependency Thomas Gleixner
2018-07-06 16:13 ` [patch 2/7] x86/kvmclock: Remove page size requirement from wall_clock Thomas Gleixner
2018-07-12  2:15   ` Pavel Tatashin
2018-07-06 16:13 ` [patch 3/7] x86/kvmclock: Decrapify kvm_register_clock() Thomas Gleixner
2018-07-06 17:38   ` Paolo Bonzini
2018-07-06 17:39     ` Thomas Gleixner
2018-07-12  2:24   ` Pavel Tatashin
2018-07-06 16:13 ` [patch 4/7] x86/kvmclock: Cleanup the code Thomas Gleixner
2018-07-06 17:39   ` Paolo Bonzini
2018-07-09  9:05   ` Peter Zijlstra
2018-07-09 10:03     ` Thomas Gleixner
2018-07-09 11:32     ` Paolo Bonzini
2018-07-06 16:13 ` [patch 5/7] x86/kvmclock: Mark variables __initdata and __ro_after_init Thomas Gleixner
2018-07-12  2:31   ` Pavel Tatashin
2018-07-06 16:13 ` [patch 6/7] x86/kvmclock: Move kvmclock vsyscall param and init to kvmclock Thomas Gleixner
2018-07-06 17:43   ` Paolo Bonzini
2018-07-06 19:23     ` Thomas Gleixner
2018-07-12  2:52   ` Pavel Tatashin
2018-07-06 16:13 ` [patch 7/7] x86/kvmclock: Switch kvmclock data to a PER_CPU variable Thomas Gleixner
2018-07-12  3:12   ` Pavel Tatashin
2018-07-06 17:47 ` [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups Paolo Bonzini
2018-07-06 23:51   ` Brijesh Singh
2018-07-09  9:22 ` [patch 8/7] x86/kvmclock: Avoid TSC recalibration Peter Zijlstra
2018-07-12  2:12 ` [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups Pavel Tatashin
2018-07-13 22:51   ` Thomas Gleixner
2018-07-14  0:20     ` Pavel Tatashin

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