From: Paul Durrant <xadimgnik@gmail.com>
To: "'Jan Beulich'" <jbeulich@suse.com>
Cc: xen-devel@lists.xenproject.org,
"'Paul Durrant'" <pdurrant@amazon.com>,
"'Roger Pau Monné'" <roger.pau@citrix.com>,
"'Wei Liu'" <wl@xen.org>,
"'Andrew Cooper'" <andrew.cooper3@citrix.com>
Subject: RE: [PATCH v2 2/2] x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt()
Date: Fri, 31 Jul 2020 14:07:54 +0100 [thread overview]
Message-ID: <004501d6673b$9adffbf0$d09ff3d0$@xen.org> (raw)
In-Reply-To: <a4856c33-8bb0-4afa-cc71-3af4c229bc27@suse.com>
> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: 31 July 2020 13:58
> To: Paul Durrant <paul@xen.org>
> Cc: xen-devel@lists.xenproject.org; Paul Durrant <pdurrant@amazon.com>; Andrew Cooper
> <andrew.cooper3@citrix.com>; Wei Liu <wl@xen.org>; Roger Pau Monné <roger.pau@citrix.com>
> Subject: Re: [PATCH v2 2/2] x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt()
>
> On 31.07.2020 14:39, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@amazon.com>
> >
> > Re-factor the code to take advantage of the fact that the APIC access page is
> > a 'special' page.
>
> Hmm, that's going quite as far as I was thinking to go: In
> particular, you leave in place the set_mmio_p2m_entry() use
> in vmx_alloc_vlapic_mapping(). With that replaced, the
> re-ordering in epte_get_entry_emt() that you do shouldn't
> be necessary; you'd simple drop the checking of the
> specific MFN.
Ok, it still needs to go in the p2m though so are you suggesting just calling p2m_set_entry() directly?
> However, ...
>
> > --- a/xen/arch/x86/hvm/mtrr.c
> > +++ b/xen/arch/x86/hvm/mtrr.c
> > @@ -814,29 +814,22 @@ int epte_get_entry_emt(struct domain *d, unsigned long gfn, mfn_t mfn,
> > return -1;
> > }
> >
> > - if ( direct_mmio )
> > - {
> > - if ( (mfn_x(mfn) ^ mfn_x(d->arch.hvm.vmx.apic_access_mfn)) >> order )
> > - return MTRR_TYPE_UNCACHABLE;
> > - if ( order )
> > - return -1;
>
> ... this part of the logic wants retaining, I think, i.e.
> reporting back to the guest that the mapping needs splitting.
> I'm afraid I have to withdraw my R-b on patch 1 for this
> reason, as the check needs to be added there already.
To be clear... You mean I need the:
if ( order )
return -1;
there?
Paul
>
> Jan
next prev parent reply other threads:[~2020-07-31 13:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 12:39 [PATCH v2 0/2] epte_get_entry_emt() modifications Paul Durrant
2020-07-31 12:39 ` [PATCH v2 1/2] x86/hvm: set 'ipat' in EPT for special pages Paul Durrant
2020-07-31 12:39 ` [PATCH v2 2/2] x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt() Paul Durrant
2020-07-31 12:58 ` Jan Beulich
2020-07-31 13:07 ` Paul Durrant [this message]
2020-07-31 13:40 ` Jan Beulich
2020-07-31 13:43 ` Paul Durrant
2020-07-31 13:54 ` Paul Durrant
2020-07-31 14:14 ` Jan Beulich
2020-07-31 13:45 ` Durrant, Paul
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