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From: Nadav Amit <namit@vmware.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	the arch/x86 maintainers <x86@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi()
Date: Wed, 26 Jun 2019 02:39:45 +0000
Message-ID: <401C4384-98A1-4C27-8F71-4848F4B4A440@vmware.com> (raw)
In-Reply-To: <cb28f2b4-92f0-f075-648e-dddfdbdd2e3c@intel.com>

> On Jun 25, 2019, at 2:40 PM, Dave Hansen <dave.hansen@intel.com> wrote:
> 
> On 6/12/19 11:48 PM, Nadav Amit wrote:
>> Support the new interface of flush_tlb_multi, which also flushes the
>> local CPU's TLB, instead of flush_tlb_others that does not. This
>> interface is more performant since it parallelize remote and local TLB
>> flushes.
>> 
>> The actual implementation of flush_tlb_multi() is almost identical to
>> that of flush_tlb_others().
> 
> This confused me a bit.  I thought we didn't support paravirtualized
> flush_tlb_multi() from reading earlier in the series.
> 
> But, it seems like that might be Xen-only and doesn't apply to KVM and
> paravirtualized KVM has no problem supporting flush_tlb_multi().  Is
> that right?  It might be good to include some of that background in the
> changelog to set the context.

I’ll try to improve the change-logs a bit. There is no inherent reason for
PV TLB-flushers not to implement their own flush_tlb_multi(). It is left
for future work, and here are some reasons:

1. Hyper-V/Xen TLB-flushing code is not very simple
2. I don’t have a proper setup
3. I am lazy



  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190613064813.8102-1-namit@vmware.com>
2019-06-13  6:48 ` [PATCH 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently Nadav Amit
2019-06-25 21:29   ` Dave Hansen
2019-06-26  2:35     ` Nadav Amit
2019-06-26  3:00       ` Dave Hansen
2019-06-26  3:32         ` Nadav Amit
2019-06-26  3:36   ` Andy Lutomirski
2019-06-26  3:48     ` Nadav Amit
2019-06-26  3:51       ` Andy Lutomirski
2019-06-13  6:48 ` [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi() Nadav Amit
2019-06-25 21:40   ` Dave Hansen
2019-06-26  2:39     ` Nadav Amit [this message]
2019-06-26  3:35       ` Andy Lutomirski
2019-06-26  3:41         ` Nadav Amit
2019-06-26  3:56           ` Andy Lutomirski
2019-06-26  6:30             ` Nadav Amit
2019-06-26 16:37               ` Andy Lutomirski
2019-06-26 17:41                 ` Vitaly Kuznetsov
2019-06-26 18:21                   ` Andy Lutomirski

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