From: Paolo Bonzini <pbonzini@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>, kvm <kvm@vger.kernel.org>
Subject: Re: KVM x86: Infinite loop on updating accessed bit in r/o page table
Date: Tue, 25 Feb 2014 15:11:37 +0100 [thread overview]
Message-ID: <530CA499.9070401@redhat.com> (raw)
In-Reply-To: <530C7D19.2000409@siemens.com>
Il 25/02/2014 12:23, Jan Kiszka ha scritto:
>> > even though OVMF sets the accessed/dirty bits so it's not exactly the same
>> > scenario.
>> >
>> > Note that NPT simply does not support this. Page tables must be writable
>> > in the NPT page tables, according to the AMD manual.
> We could still emulate the instruction in such a case to get beyond the
> write fault. Slow but more correct, I suppose.
They must be writable always, even if A=D=1. So the only solution would
be to emulate everything that puts page tables in ROMs, which is really
too slow to be viable. We're really talking 50-100 times slower than
bare metal.
Paolo
prev parent reply other threads:[~2014-02-25 14:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-24 18:29 KVM x86: Infinite loop on updating accessed bit in r/o page table Jan Kiszka
2014-02-25 10:57 ` Paolo Bonzini
2014-02-25 11:23 ` Jan Kiszka
2014-02-25 14:11 ` Paolo Bonzini [this message]
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