linux-kernel - Re: [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb

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Message-ID: <cb28f2b4-92f0-f075-648e-dddfdbdd2e3c@intel.com>
Date:   Tue, 25 Jun 2019 14:40:48 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Nadav Amit <namit@...are.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi()

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.