From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: [PATCH v2] x86/hvm: re-work viridian APIC assist code Date: Wed, 05 Sep 2018 10:40:22 +0100 Message-ID: <1536140422.31549.59.camel@infradead.org> References: <20180118151059.1336-1-paul.durrant@citrix.com> <1535153880.24926.28.camel@infradead.org> <1536093061.31549.47.camel@infradead.org> <88abe6b0dee947ad93af543653dde12a@AMSPEX02CL03.citrite.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0579345612145324035==" Return-path: Received: from us1-rack-dfw2.inumbo.com ([104.130.134.6]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1fxUIW-0001W6-S8 for xen-devel@lists.xenproject.org; Wed, 05 Sep 2018 09:40:29 +0000 In-Reply-To: <88abe6b0dee947ad93af543653dde12a@AMSPEX02CL03.citrite.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" To: Paul Durrant , "xen-devel@lists.xenproject.org" Cc: Eslam Elnikety , Andrew Cooper , Shan Haitao , Jan Beulich List-Id: xen-devel@lists.xenproject.org --===============0579345612145324035== Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-1T7Oe4GASWDXphGhIbnn" --=-1T7Oe4GASWDXphGhIbnn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2018-09-05 at 09:36 +0000, Paul Durrant wrote: >=20 > 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. --=-1T7Oe4GASWDXphGhIbnn Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEFQw ggUxMIIEGaADAgECAhBNRhEyk/HZ7naOeTHWrzuAMA0GCSqGSIb3DQEBCwUAMIGXMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYD VQQKExFDT01PRE8gQ0EgTGltaXRlZDE9MDsGA1UEAxM0Q09NT0RPIFJTQSBDbGllbnQgQXV0aGVu dGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTAeFw0xNzEyMjEwMDAwMDBaFw0xODEyMjEyMzU5 NTlaMCQxIjAgBgkqhkiG9w0BCQEWE2R3bXcyQGluZnJhZGVhZC5vcmcwggEiMA0GCSqGSIb3DQEB AQUAA4IBDwAwggEKAoIBAQDgzLNWa18DNpGUj/ZeH0Sgz53ESIbzdPw3OJeuNP6jZhxZojbyfxbM hETscxI/Hj6UZ4a7sHm5BkVjlsB1Af2Za/PXUt8MmLAcPMHkMPGunvkUibEvblDvpqMkQZlaZM+t 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