From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, luto@amacapital.net,
linux-kernel@vger.kernel.org, x86@kernel.org,
Lai Jiangshan <laijs@linux.alibaba.com>,
andrew.cooper3@citrix.com, daniel.thompson@linaro.org,
a.darwish@linutronix.de, rostedt@goodmis.org,
bigeasy@linutronix.de, Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH 08/14] x86/entry: Optimize local_db_save() for virt
Date: Tue, 2 Jun 2020 18:17:17 -0700 [thread overview]
Message-ID: <20200603011716.GC24169@linux.intel.com> (raw)
In-Reply-To: <20200529213321.187833200@infradead.org>
On Fri, May 29, 2020 at 11:27:36PM +0200, Peter Zijlstra wrote:
> Because DRn access is 'difficult' with virt; but the DR7 read is
> cheaper than a cacheline miss on native, add a virt specific
> fast path to local_db_save(), such that when breakpoints are not in
> use we avoid touching DRn entirely.
>
> Suggested-by: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/x86/include/asm/debugreg.h | 7 ++++++-
> arch/x86/kernel/hw_breakpoint.c | 26 ++++++++++++++++++++++----
> arch/x86/kvm/vmx/nested.c | 2 +-
> 3 files changed, 29 insertions(+), 6 deletions(-)
...
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3028,9 +3028,9 @@ static int nested_vmx_check_vmentry_hw(s
> /*
> * VMExit clears RFLAGS.IF and DR7, even on a consistency check.
> */
> - local_irq_enable();
> if (hw_breakpoint_active())
> set_debugreg(__this_cpu_read(cpu_dr7), 7);
> + local_irq_enable();
> preempt_enable();
This should be a separate patch, probably with:
Cc: stable@vger.kernel.org
Fixes: 52017608da33 ("KVM: nVMX: add option to perform early consistency checks via H/W")
next prev parent reply other threads:[~2020-06-03 1:17 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 21:27 [PATCH 00/14] x86/entry: disallow #DB more and x86/entry lockdep/nmi Peter Zijlstra
2020-05-29 21:27 ` [PATCH 01/14] x86/hw_breakpoint: Add within_area() to check data breakpoints Peter Zijlstra
2020-05-29 21:27 ` [PATCH 02/14] x86/hw_breakpoint: Prevent data breakpoints on direct GDT Peter Zijlstra
2020-05-30 12:45 ` Andrew Cooper
2020-05-30 15:15 ` Lai Jiangshan
2020-05-29 21:27 ` [PATCH 03/14] x86/hw_breakpoint: Prevent data breakpoints on per_cpu cpu_tss_rw Peter Zijlstra
2020-05-29 21:27 ` [PATCH 04/14] x86/hw_breakpoint: Prevent data breakpoints on user_pcid_flush_mask Peter Zijlstra
2020-05-29 21:27 ` [PATCH 05/14] x86/entry: Introduce local_db_{save,restore}() Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 06/14] x86/entry, nmi: Disable #DB Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 07/14] x86/entry, mce: Disallow #DB during #MC Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 08/14] x86/entry: Optimize local_db_save() for virt Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-03 1:17 ` Sean Christopherson [this message]
2020-05-29 21:27 ` [PATCH 09/14] x86/entry: Remove debug IDT frobbing Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 10/14] x86/entry: Remove DBn stacks Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 11/14] x86/entry: Clarify irq_{enter,exit}_rcu() Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-02 14:42 ` [PATCH 11/14] " Qian Cai
2020-06-02 15:05 ` Peter Zijlstra
2020-06-02 18:47 ` Qian Cai
2020-06-03 17:50 ` [tip: x86/entry] x86/entry: Use __irq_exit_rcu() in irq_exit() tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 12/14] x86/entry: Rename trace_hardirqs_off_prepare() Peter Zijlstra
2020-05-30 9:57 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-05-29 21:27 ` [PATCH 13/14] lockdep: Prepare for NMI IRQ state tracking Peter Zijlstra
2020-05-29 22:14 ` Steven Rostedt
2020-05-29 22:25 ` Peter Zijlstra
2020-05-29 22:28 ` Steven Rostedt
2020-05-29 22:33 ` Peter Zijlstra
2020-06-02 20:00 ` Peter Zijlstra
2020-05-29 21:27 ` [PATCH 14/14] x86/entry: Fix NMI vs " Peter Zijlstra
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