From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Nadav Amit <namit@vmware.com>, Alexander Graf <graf@amazon.com>,
Ajay Kaher <akaher@vmware.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
Srivatsa Bhat <srivatsab@vmware.com>,
"srivatsa@csail.mit.edu" <srivatsa@csail.mit.edu>,
Alexey Makhalov <amakhalov@vmware.com>,
Vasavi Sirnapalli <vsirnapalli@vmware.com>,
"er.ajay.kaher@gmail.com" <er.ajay.kaher@gmail.com>,
"willy@infradead.org" <willy@infradead.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"jailhouse-dev@googlegroups.com" <jailhouse-dev@googlegroups.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"acrn-dev@lists.projectacrn.org" <acrn-dev@lists.projectacrn.org>,
"helgaas@kernel.org" <helgaas@kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v2] x86/PCI: Prefer MMIO over PIO on all hypervisor
Date: Tue, 04 Oct 2022 10:30:10 +0200 [thread overview]
Message-ID: <87lepw9ejx.fsf@redhat.com> (raw)
In-Reply-To: <04F550C5-786A-4B8E-9A88-EBFBD8872F16@vmware.com>
Nadav Amit <namit@vmware.com> writes:
> On Oct 3, 2022, at 8:03 AM, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
>> Not my but rather PCI maintainer's call but IMHO dropping 'const' is
>> better, introducing a new global var is our 'last resort' and should be
>> avoided whenever possible. Alternatively, you can add a
>> raw_pci_ext_ops_preferred() function checking somethin within 'struct
>> hypervisor_x86' but I'm unsure if it's better.
>>
>> Also, please check Alex' question/suggestion.
>
> Here is my take (and Ajay knows probably more than me):
>
> Looking briefly on MCFG, I do not see a clean way of using the ACPI table.
> The two options are either to use a reserved field (which who knows, might
> be used one day) or some OEM ID. I am also not familiar with
> PCI_COMMAND.MEMORY=0, so Ajay can hopefully give some answer about that.
>
> Anyhow, I understand (although not relate) to the objection for a new global
> variable. How about explicitly calling this hardware bug a “bug” and using
> the proper infrastructure? Calling it explicitly a bug may even push whoever
> can to resolve it.
>
> IOW, how about doing something along the lines of (not tested):
>
Works for me. Going forward, the intention shoud be to also clear the
bug on other x86 hypervisors, e.g. we test modern Hyper-V versions and
if MMIO works well we clear it, we test modern QEMU/KVM setups and if
MMIO works introduce a feature bit somewhere and also clear the bug in
the guest when the bit is set.
--
Vitaly
next prev parent reply other threads:[~2022-10-04 8:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 12:47 [PATCH v2] x86/PCI: Prefer MMIO over PIO on all hypervisor Ajay Kaher
2022-09-13 13:34 ` Vitaly Kuznetsov
2022-09-29 5:36 ` Ajay Kaher
2022-09-29 9:12 ` Alexander Graf
2022-10-03 15:03 ` Vitaly Kuznetsov
2022-10-03 17:34 ` Nadav Amit
2022-10-03 21:06 ` H. Peter Anvin
2022-10-03 21:28 ` Nadav Amit
2022-10-03 23:51 ` H. Peter Anvin
2022-10-04 0:19 ` Nadav Amit
2022-10-04 8:22 ` Alexander Graf
2022-10-04 18:48 ` Nadav Amit
2022-10-10 14:58 ` Nadav Amit
2022-10-10 17:05 ` Michael S. Tsirkin
2022-10-04 8:30 ` Vitaly Kuznetsov [this message]
2022-10-03 21:01 ` H. Peter Anvin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87lepw9ejx.fsf@redhat.com \
--to=vkuznets@redhat.com \
--cc=acrn-dev@lists.projectacrn.org \
--cc=akaher@vmware.com \
--cc=amakhalov@vmware.com \
--cc=bhelgaas@google.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=er.ajay.kaher@gmail.com \
--cc=graf@amazon.com \
--cc=helgaas@kernel.org \
--cc=hpa@zytor.com \
--cc=jailhouse-dev@googlegroups.com \
--cc=kvm@vger.kernel.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namit@vmware.com \
--cc=rostedt@goodmis.org \
--cc=srivatsa@csail.mit.edu \
--cc=srivatsab@vmware.com \
--cc=tglx@linutronix.de \
--cc=vsirnapalli@vmware.com \
--cc=willy@infradead.org \
--cc=x86@kernel.org \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).