From: David Woodhouse <dwmw2@infradead.org>
To: Paul Durrant <Paul.Durrant@citrix.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Eslam Elnikety <elnikety@amazon.de>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
Shan Haitao <haitao.shan@intel.com>,
Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH v2] x86/hvm: re-work viridian APIC assist code
Date: Wed, 05 Sep 2018 10:40:22 +0100 [thread overview]
Message-ID: <1536140422.31549.59.camel@infradead.org> (raw)
In-Reply-To: <88abe6b0dee947ad93af543653dde12a@AMSPEX02CL03.citrite.net>
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On Wed, 2018-09-05 at 09:36 +0000, Paul Durrant wrote:
>
> I see. Given that Windows has used APIC assist to circumvent its EOI
> then I wonder whether we can get away with essentially doing the
> same. I.e. for a completed APIC assist found in
> vlapic_has_pending_irq() we simply clear the APIC assist and highest
> vector in the ISR, rather than calling through to vlapic_EOI_set()
> and suffering the overhead. I'll spin up a patch and give it a whirl.
I think that's fine if you don't actually pass unmaskable MSIs through
to the guest in question, but if you *do* then you still need the EOI
to happen properly to "unmask" it.
Hence my approach which is basically doing what you said and bypassing
the expensive part of hvm_dpci_msi_eoi(), but *only* if there's no
unmaskable MSI to worry about.
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next prev parent reply other threads:[~2018-09-05 9:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-18 15:10 [PATCH v2] x86/hvm: re-work viridian APIC assist code Paul Durrant
2018-01-18 16:21 ` Jan Beulich
2018-01-18 16:27 ` Paul Durrant
2018-08-24 23:38 ` David Woodhouse
2018-09-03 10:12 ` Paul Durrant
2018-09-04 20:31 ` David Woodhouse
2018-09-05 9:36 ` Paul Durrant
2018-09-05 9:40 ` David Woodhouse [this message]
2018-09-05 9:43 ` Paul Durrant
2018-09-05 10:40 ` Paul Durrant
2018-09-05 10:45 ` David Woodhouse
2018-09-05 10:48 ` Paul Durrant
2020-08-11 13:25 ` [Xen-devel] " David Woodhouse
2020-08-12 13:43 ` Roger Pau Monné
2020-08-13 8:10 ` Paul Durrant
2020-08-13 9:45 ` Roger Pau Monné
2020-08-14 14:13 ` David Woodhouse
2020-08-14 14:41 ` Roger Pau Monné
2020-08-19 7:12 ` Jan Beulich
2020-08-19 8:26 ` Roger Pau Monné
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