From: Andrew Cooper <andrew.cooper3@citrix.com>
To: xen devel <xen-devel@lists.xensource.com>
Subject: APIC MSRs query
Date: Tue, 17 May 2011 14:25:52 +0100 [thread overview]
Message-ID: <4DD27760.9020706@citrix.com> (raw)
Hello,
I am currently cleaning up the APIC code for the sake of
shutdown/reboot/crashdump and have a query about the (modified for
brevity) snippet of code:
uint64_t msr_content;
rdmsrl(MSR_IA32_APICBASE, msr_content);
msr_content |= MSR_IA32_APICBASE_ENABLE | MSR_IA32_APICBASE_EXTD;
msr_content = (uint32_t)msr_content;
wrmsrl(MSR_IA32_APICBASE, msr_content);
which is added into apic.c in changeset b622e411eef8, and has propagated
elsewhere in the codebase during subsequent cleanups etc.
The MP spec and x2apic spec states that bits [35:12] of
MSR_IA32_APICBASE is the base APIC MMIO address. Is there reason why
the code (almost always) clears the top 4 bits, or is it just an
overlooked mistake?
--
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com
next reply other threads:[~2011-05-17 13:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-17 13:25 Andrew Cooper [this message]
2011-05-17 13:43 ` APIC MSRs query Jan Beulich
2011-05-17 13:49 ` Andrew Cooper
2011-05-17 13:59 ` Ian Campbell
2011-05-17 14:08 ` Andrew Cooper
2011-05-17 14:08 ` Jan Beulich
2011-05-17 14:53 ` Keir Fraser
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