linux-kernel - Re: [PATCH RFC 0/4] KVM: MIPS: Provide arch-specific kvm_flush_remote

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Message-ID: <20200311183201.GK479302@xz-x1>
Date:   Wed, 11 Mar 2020 14:32:01 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-mips@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH RFC 0/4] KVM: MIPS: Provide arch-specific
 kvm_flush_remote_tlbs()

On Wed, Feb 12, 2020 at 01:25:30PM +0100, Paolo Bonzini wrote:
> On 07/02/20 23:35, Peter Xu wrote:
> > [This series is RFC because I don't have MIPS to compile and test]
> > 
> > kvm_flush_remote_tlbs() can be arch-specific, by either:
> > 
> > - Completely replace kvm_flush_remote_tlbs(), like ARM, who is the
> >   only user of CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL so far
> > 
> > - Doing something extra before kvm_flush_remote_tlbs(), like MIPS VZ
> >   support, however still wants to have the common tlb flush to be part
> >   of the process.  Could refer to kvm_vz_flush_shadow_all().  Then in
> >   MIPS it's awkward to flush remote TLBs: we'll need to call the mips
> >   hooks.
> > 
> > It's awkward to have different ways to specialize this procedure,
> > especially MIPS cannot use the genenal interface which is quite a
> > pity.  It's good to make it a common interface.
> > 
> > This patch series removes the 2nd MIPS usage above, and let it also
> > use the common kvm_flush_remote_tlbs() interface.  It should be
> > suggested that we always keep kvm_flush_remote_tlbs() be a common
> > entrance for tlb flushing on all archs.
> > 
> > This idea comes from the reading of Sean's patchset on dynamic memslot
> > allocation, where a new dirty log specific hook is added for flushing
> > TLBs only for the MIPS code [1].  With this patchset, logically the
> > new hook in that patch can be dropped so we can directly use
> > kvm_flush_remote_tlbs().
> > 
> > TODO: We can even extend another common interface for ranged TLB, but
> > let's see how we think about this series first.
> > 
> > Any comment is welcomed, thanks.
> > 
> > Peter Xu (4):
> >   KVM: Provide kvm_flush_remote_tlbs_common()
> >   KVM: MIPS: Drop flush_shadow_memslot() callback
> >   KVM: MIPS: Replace all the kvm_flush_remote_tlbs() references
> >   KVM: MIPS: Define arch-specific kvm_flush_remote_tlbs()
> > 
> >  arch/mips/include/asm/kvm_host.h |  7 -------
> >  arch/mips/kvm/Kconfig            |  1 +
> >  arch/mips/kvm/mips.c             | 22 ++++++++++------------
> >  arch/mips/kvm/trap_emul.c        | 15 +--------------
> >  arch/mips/kvm/vz.c               | 14 ++------------
> >  include/linux/kvm_host.h         |  1 +
> >  virt/kvm/kvm_main.c              | 10 ++++++++--
> >  7 files changed, 23 insertions(+), 47 deletions(-)
> > 
> 
> Compile-tested and queued.

Just in case it fells through the crach - Paolo, do you still have
plan to queue this again?

Thanks,

-- 
Peter Xu