From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Message-ID: <1489666647.4195.238.camel@infradead.org> Subject: Re: [PATCH v2] arm64: pci: add support for pci_mmap_page_range From: David Woodhouse To: Will Deacon , Jerin Jacob In-Reply-To: <20160415130953.GI22906@arm.com> References: <1460581856-12380-1-git-send-email-jerin.jacob@caviumnetworks.com> <20160415130953.GI22906@arm.com> Date: Thu, 16 Mar 2017 12:17:27 +0000 Mime-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lorenzo.pieralisi@arm.com, benh@kernel.crashing.org, david.daney@cavium.com, catalin.marinas@arm.com, Liviu.Dudau@arm.com, rrichter@cavium.com, hanjun.guo@linaro.org, linux-pci , bhelgaas@google.com, linux-arm-kernel@lists.infradead.org Content-Type: multipart/mixed; boundary="===============0611751714314708911==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+bjorn=helgaas.com@lists.infradead.org List-ID: --===============0611751714314708911== Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-QiavzKSAeIYy0/qqcWmi" --=-QiavzKSAeIYy0/qqcWmi Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2016-04-15 at 14:09 +0100, Will Deacon wrote: >=20 > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (write_combine) > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0vma->vm_page_prot =3D pgprot_writecombine(vma->vm_page_prot); > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0else > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0vma->vm_page_prot =3D pgprot_noncached(vma->vm_page_prot); >=20 > For consistency with ioremap, this should be pgprot_device. What's the difference? I note that VFIO is using pgprot_noncached() too, in vfio_pci_mmap() =E2=80= =94 where it open-codes an entirely arch-agnostic version of pci_mmap_page_range() all for itself. Should that be changed to pgprot_device() too? Let me see if I can get this straight... We have the legacy interface through /proc/bus/pci, where the user passes a "user-visible" bus address not necessarily (on platforms with HAVE_PCI_RESOURCE_TO_USER) a host physical address. The arch-specific pci_mmap_page_range() exists to work around that translation, on the two platforms which need it. It *also* has (on about three platforms) support for a write-combining mapping. The sysfs interface theough /sys/bus/pci/devices/*/resource* probably doesn't need to use pci_mmap_page_range() at all, *except* for the 'resourceX_wc' variant which has write-combining support. How about we do the following (probably not in this order): =C2=A0=E2=80=A2 Kill pci_mmap_page_range() entirely. =C2=A0=E2=80=A2 Implement a generic version which has (arch-assisted) WC su= pport =C2=A0 =C2=A0but no knowledge of the horrid pci_resource_to_user() mapping. =C2=A0=E2=80=A2 Require pci_user_to_resource() to be provided by platforms = with =C2=A0 =C2=A0HAVE_ARCH_PCI_RESOURCE_TO_USER, and call that from *generic* c= ode, =C2=A0 =C2=A0for the legacy procfs interface, before invoking the generic =C2=A0 =C2=A0replacement for pci_mmap_page_range(). (Yes, we still need to support mmap of I/O resources on... is it only powerpc? And there are a few inconsistencies, like powerpc forcing WC even on the sysfs files that *don't* have _wc in their name, that probably want to be cleaned up as we consolidate...) --=-QiavzKSAeIYy0/qqcWmi Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCDzUw ggSvMIIDl6ADAgECAhEA4CPLFRKDU4mtYW56VGdrITANBgkqhkiG9w0BAQsFADBvMQswCQYDVQQG EwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRU UCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MB4XDTE0MTIyMjAw MDAwMFoXDTIwMDUzMDEwNDgzOFowgZsxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1h bmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMUEw PwYDVQQDEzhDT01PRE8gU0hBLTI1NiBDbGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBF bWFpbCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAImxDdp6UxlOcFIdvFamBia3 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