From: Jan Beulich <jbeulich@suse.com>
To: Wei Chen <wei.chen@arm.com>
Cc: nd@arm.com, "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
"George Dunlap" <george.dunlap@citrix.com>,
"Julien Grall" <julien@xen.org>,
"Stefano Stabellini" <sstabellini@kernel.org>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH v5 2/6] xen/x86: move generically usable NUMA code from x86 to common
Date: Tue, 27 Sep 2022 11:39:53 +0200 [thread overview]
Message-ID: <504534ec-32bf-0bab-7a61-86d75b6e1f71@suse.com> (raw)
In-Reply-To: <359e87d9-aec7-2198-86ab-1d0f76bf567d@suse.com>
On 27.09.2022 10:19, Jan Beulich wrote:
> On 20.09.2022 11:12, Wei Chen wrote:
>> +static unsigned int __init extract_lsb_from_nodes(const struct node *nodes,
>> + nodeid_t numnodes)
>> +{
>> + unsigned int i, nodes_used = 0;
>> + unsigned long spdx, epdx;
>> + unsigned long bitfield = 0, memtop = 0;
>> +
>> + for ( i = 0; i < numnodes; i++ )
>> + {
>> + spdx = paddr_to_pdx(nodes[i].start);
>> + epdx = paddr_to_pdx(nodes[i].end - 1) + 1;
>> +
>> + if ( spdx >= epdx )
>> + continue;
>> +
>> + bitfield |= spdx;
>
> Perhaps to be taken care of in a separate patch: We accumulate only
> the bits from the start addresses here, contrary to what the comment
> ahead of the function says (and I think it is the comment which is
> putting things correctly).
It's the comment which is wrong - it wasn't updated in Linux commit
54413927f022 ("x86-64: x86_64-make-the-numa-hash-function-nodemap-allocation
fix fix"). Our code was cloned from Linux'es. In fact when memory is not
contiguous, too small a shift value might be determined. This in particular
also may matter for the lowest range covered by any node: On x86 this will
always start at zero (and hence won't influence the final calculation), but
iirc on Arm memory may (and typically will) start at non-zero addresses. In
such a case the first node's start address should be ignored, as it's fine
to (kind of) associate all lower addresses (where no memory is) with this
same node. But that's now indeed something which will want taking care of
while making the code usable for other architectures.
Jan
next prev parent reply other threads:[~2022-09-27 9:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-20 9:12 [PATCH v5 0/6] Device tree based NUMA support for Arm - Part#2 Wei Chen
2022-09-20 9:12 ` [PATCH v5 1/6] xen/x86: Provide helpers for common code to access acpi_numa Wei Chen
2022-09-27 7:37 ` Jan Beulich
2022-09-29 6:29 ` Wei Chen
2022-09-20 9:12 ` [PATCH v5 2/6] xen/x86: move generically usable NUMA code from x86 to common Wei Chen
2022-09-27 8:19 ` Jan Beulich
2022-09-27 9:39 ` Jan Beulich [this message]
2022-09-29 7:58 ` Wei Chen
2022-09-29 7:43 ` Wei Chen
2022-09-29 12:14 ` Jan Beulich
2022-09-30 1:45 ` Wei Chen
2022-09-20 9:12 ` [PATCH v5 3/6] xen/x86: Use ASSERT instead of VIRTUAL_BUG_ON for phys_to_nid Wei Chen
2022-09-20 9:12 ` [PATCH v5 4/6] xen/x86: use arch_get_ram_range to get information from E820 map Wei Chen
2022-09-20 9:12 ` [PATCH v5 5/6] xen/x86: move NUMA scan nodes codes from x86 to common Wei Chen
2022-09-27 15:48 ` Jan Beulich
2022-09-29 8:21 ` Wei Chen
2022-09-29 12:21 ` Jan Beulich
2022-09-30 1:40 ` Wei Chen
2022-09-30 6:03 ` Jan Beulich
2022-10-09 7:25 ` Wei Chen
2022-10-10 7:03 ` Wei Chen
2022-10-10 8:25 ` Jan Beulich
2022-09-20 9:12 ` [PATCH v5 6/6] xen: introduce a Kconfig option to configure NUMA nodes number Wei Chen
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