On 08/15/2012 06:54 AM, Jacob Shin wrote:
On Tue, Aug 14, 2012 at 04:34:39PM +0800, Dave Young wrote:
On 08/14/2012 05:46 AM, Jacob Shin wrote:
Currently kernel direct mappings are created for all pfns between
[ 0 to max_low_pfn ) and [ 4GB to max_pfn ). When we introduce memory
holes, we end up mapping memory ranges that are not backed by physical
DRAM. This is fine for lower memory addresses which can be marked as UC
by fixed/variable range MTRRs, however we run in to trouble with high
addresses.
The following patchset creates direct mappings only for E820_RAM regions
between 0 ~ max_low_pfn and 4GB ~ max_pfn. And leaves non-E820_RAM and
memory holes unmapped.
Hi,
Chaowang did some kdump test in a kvm guest with this patchset, 2nd
kenrel just reboot after some ACPI printk, see below dmesg of 2nd kernel:
Hello, thanks for testing, since I have not tested under KVM .. I also have
not tested passing in user supplied memory maps as your kernel log suggests.
Looking into this, it seems like we get a page fault while trying to set up
fixmap for the APIC. I think the fixmap is set up even before we get to
setup_arch(), and it is sitting in memory that is not marked as usable by
your user supplied e820.
Could you give V3 a try? I just sent it out a minute ago, this version
won't try to remap what has already been mapped as part of the boot process
before we get to setup_arch, it'll just take what its given.
Hi, Jacob
I just tried v3 patchset in my x86_64 kvm guest, it was booting
successfully and the issue mentioned is gone.
-WANG Chao
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