Re: [PATCH] KVM: MTRR: fix fixed MTRR segment look up

[Paolo Bonzini <pbonzini@redhat.com>]

On 14/12/2015 17:06, Alexis D...t wrote:
> From what I see in my case, it was especially gfn from 0x0 to 0xA0
> which are deadly impacted by the wrong cache property.

Yes, indeed.  I'll send the patch to Linus this week; I've now posted to
the BZ a second patch for GFNs above 4GB.

Paolo

> 2015-12-14 16:36 GMT+01:00 Paolo Bonzini <pbonzini@redhat.com>:
>> >
>> >
>> > On 14/12/2015 15:39, Alexis D...t wrote:
>>> >> It fixes the slow-down of VM running with pci-passthrough, since some MTRR
>>> >> range changed from MTRR_TYPE_WRBACK to MTRR_TYPE_UNCACHABLE.
>>> >>
>>> >> Fixes: fa61213746a ("KVM: MTRR: simplify kvm_mtrr_get_guest_memory_type")
>>> >> Bugzilla: (https://bugzilla.kernel.org/show_bug.cgi?id=107561)
>>> >>
>>> >> Signed-off-by: Alexis Dambricourt <alexis.dambricourt@gmail.com>
>>> >> ---
>>> >>  arch/x86/kvm/mtrr.c | 2 +-
>>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>>> >>
>>> >> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
>>> >> index 9e8bf13..adc54e1 100644
>>> >> --- a/arch/x86/kvm/mtrr.c
>>> >> +++ b/arch/x86/kvm/mtrr.c
>>> >> @@ -267,7 +267,7 @@ static int fixed_mtrr_addr_to_seg(u64 addr)
>>> >>
>>> >>         for (seg = 0; seg < seg_num; seg++) {
>>> >>                 mtrr_seg = &fixed_seg_table[seg];
>>> >> -               if (mtrr_seg->start >= addr && addr < mtrr_seg->end)
>>> >> +               if (mtrr_seg->start <= addr && addr < mtrr_seg->end)