From: Juergen Gross <jgross@suse.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v4 09/12] x86/mtrr: construct a memory map with cache modes
Date: Fri, 31 Mar 2023 15:23:13 +0200 [thread overview]
Message-ID: <8860c326-3ba5-bd4c-1dab-17772e8fcda0@suse.com> (raw)
In-Reply-To: <20230331125538.GBZCbYSqr8kMP4bpwS@fat_crate.local>
[-- Attachment #1.1.1: Type: text/plain, Size: 2000 bytes --]
On 31.03.23 14:55, Borislav Petkov wrote:
> On Wed, Mar 29, 2023 at 03:39:35PM +0200, Juergen Gross wrote:
>> No. :-)
>
> Because?
In general the critical case is add_map_entry_at() returning 2 (in the
case it is returning 1, the index can be set to -1, but there is always
the "continue" statement right after that, which would execute the "i++"
of the "for" statement).
add_map_entry_at() can return 2 only, if it detects "merge_prev" and
"merge_next". "merge_prev" can be set only if the current index was > 0,
which makes it impossible to return 2 if the index was 0.
>> The final form of the code is the result of an iterative process. :-)
>
> I have a similar iterative process: until it hasn't been reviewed and
> explained properly, this is not going anywhere.
Of course.
> So however you wanna do it, fine by me.
>
>> I've reused the wording from cleanup.c (just above amd_special_default_mtrr()).
>
> That got added with K8. K8 is ancient history so nothing magic about
> that anymore. It is basically a bit in the SYSCFG MSR which says that
>
> [4G ... TOP_MEM2]
>
> is WB.
How should it be named? AMD TOP_MEM2 MSR?
>>> Why not in mtrr_bp_init()? That is the first CPU.
>>
>> Yeah, but generic_set_mtrr() can be called after boot, too.
>
> That function sets a single MTRR register so you'd have to merge the
> ranges, AFAICT. Not rebuild the whole map...
The problem isn't an added MTRR register, but a possibly replaced or removed
one. Handling that is much more complicated, so I've chosen to do it the simple
way.
In the end I'd expect setting of MTRRs to be a rare event, so there shouldn't be
a performance issue with that approach.
>
>> Umm, not really. I want to do the copy even in the Xen PV case.
>
> How about some comments? Or you're expecting me to be able to read your
> mind?!
Okay, I'll add some more comments.
OTOH, what was hard to write should be hard to read (just kidding).
Juergen
[-- Attachment #1.1.2: OpenPGP public key --]
[-- Type: application/pgp-keys, Size: 3149 bytes --]
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 495 bytes --]
next prev parent reply other threads:[~2023-03-31 13:23 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 16:34 [PATCH v4 00/12] x86/mtrr: fix handling with PAT but without MTRR Juergen Gross
2023-03-06 16:34 ` [PATCH v4 01/12] x86/mtrr: split off physical address size calculation Juergen Gross
2023-03-06 16:34 ` [PATCH v4 02/12] x86/mtrr: optimize mtrr_calc_physbits() Juergen Gross
2023-03-20 12:50 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 03/12] x86/mtrr: support setting MTRR state for software defined MTRRs Juergen Gross
2023-03-20 12:59 ` Huang, Kai
2023-03-20 13:47 ` Juergen Gross
2023-03-20 21:34 ` Huang, Kai
2023-03-20 22:42 ` Borislav Petkov
2023-03-21 6:01 ` Juergen Gross
2023-03-20 19:05 ` Borislav Petkov
2023-03-21 6:00 ` Juergen Gross
2023-03-21 10:30 ` Borislav Petkov
2023-03-21 15:49 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 04/12] x86/hyperv: set MTRR state when running as SEV-SNP Hyper-V guest Juergen Gross
2023-03-06 16:34 ` [PATCH v4 05/12] x86/xen: set MTRR state when running as Xen PV initial domain Juergen Gross
2023-03-07 21:47 ` Boris Ostrovsky
2023-03-23 12:43 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 06/12] x86/mtrr: replace vendor tests in MTRR code Juergen Gross
2023-03-24 16:56 ` Borislav Petkov
2023-03-27 5:43 ` Juergen Gross
2023-03-27 7:14 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 07/12] x86/mtrr: allocate mtrr_value array dynamically Juergen Gross
2023-03-20 12:25 ` Huang, Kai
2023-03-20 13:49 ` Juergen Gross
2023-03-20 15:31 ` Dave Hansen
2023-03-20 15:49 ` Juergen Gross
2023-03-26 22:05 ` Borislav Petkov
2023-03-27 5:44 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 08/12] x86/mtrr: add get_effective_type() service function Juergen Gross
2023-03-06 16:34 ` [PATCH v4 09/12] x86/mtrr: construct a memory map with cache modes Juergen Gross
2023-03-29 12:51 ` Borislav Petkov
2023-03-29 13:39 ` Juergen Gross
2023-03-31 12:55 ` Borislav Petkov
2023-03-31 13:23 ` Juergen Gross [this message]
2023-04-01 14:24 ` Borislav Petkov
2023-04-03 6:57 ` Juergen Gross
2023-03-31 12:57 ` Borislav Petkov
2023-03-31 13:35 ` Juergen Gross
2023-04-01 14:26 ` Borislav Petkov
2023-04-03 7:02 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 10/12] x86/mtrr: use new cache_map in mtrr_type_lookup() Juergen Gross
2023-03-06 16:34 ` [PATCH v4 11/12] x86/mtrr: don't let mtrr_type_lookup() return MTRR_TYPE_INVALID Juergen Gross
2023-03-06 16:34 ` [PATCH v4 12/12] x86/mm: only check uniform after calling mtrr_type_lookup() Juergen Gross
2023-03-07 21:09 ` [PATCH v4 00/12] x86/mtrr: fix handling with PAT but without MTRR Michael Kelley (LINUX)
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=8860c326-3ba5-bd4c-1dab-17772e8fcda0@suse.com \
--to=jgross@suse.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.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).