linux-kernel - Re: [PATCH] KVM: Drop gfn_to_pfn

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Message-ID: <20200305154914.GE7146@xz-x1>
Date:   Thu, 5 Mar 2020 10:49:14 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: Drop gfn_to_pfn_atomic()

On Thu, Mar 05, 2020 at 01:52:24AM +0000, linmiaohe wrote:
> Peter Xu <peterx@...hat.com> writes:
> >It's never used anywhere now.
> >
> >Signed-off-by: Peter Xu <peterx@...hat.com>
> >---
> > include/linux/kvm_host.h | 1 -
> > virt/kvm/kvm_main.c      | 6 ------
> > 2 files changed, 7 deletions(-)
> 
> It seems we prefer to use kvm_vcpu_gfn_to_pfn_atomic instead now. :)
> Patch looks good, but maybe we should update Documentation/virt/kvm/locking.rst too:
> In locking.rst:
> 	For direct sp, we can easily avoid it since the spte of direct sp is fixed
> 	to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic()
> 	to pin gfn to pfn, because after gfn_to_pfn_atomic()
> 
> Thanks.
> Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

Yes we should update the document, however instead of replacing with
the vcpu helper, I'd rather reorganize the locking doc for a bit more
because the fast page fault is not enabled for indirect sp at all,
afaict...

I'll add a pre-requisite patch to refine the document, and keep your
r-b for this patch.

Thanks,

-- 
Peter Xu