From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: Nadav Amit <namit@cs.technion.ac.il>,
gleb@kernel.org, tglx@linutronix.de, mingo@redhat.com,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: Fix page-tables reserved bits
Date: Mon, 28 Apr 2014 12:41:37 +0200 [thread overview]
Message-ID: <535E3061.2030402@redhat.com> (raw)
In-Reply-To: <20140416220409.GB15155@amt.cnet>
Il 17/04/2014 00:04, Marcelo Tosatti ha scritto:
>>>> > >> @@ -3550,9 +3550,9 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
>>>> > >> break;
>>>> > >> case PT64_ROOT_LEVEL:
>>>> > >> context->rsvd_bits_mask[0][3] = exb_bit_rsvd |
>>>> > >> - rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
>>>> > >> + rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 7);
>>>> > >> context->rsvd_bits_mask[0][2] = exb_bit_rsvd |
>>>> > >> - rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
>>>> > >> + rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 7);
>>> > >
>>> > > Bit 7 is not reserved either, for the PDPTE (its PageSize bit).
>>> > >
>> >
>> > In long mode (IA-32e), bit 7 is definitely reserved.
It's always reserved for PML4E (rsvd_bits_mask[x][3]), while for PDPTEs
it is not reserved if you have 1GB pages.
> There is a separate reserved mask for PS=1, nevermind.
>
Yeah, but the situation for IA32e rsvd_bits_mask[0][2] is exactly the
same as for PAE rsvd_bits_mask[0][1], and we're not marking the bit as
reserved there.
The right thing to do is to add rsvd_bits(7, 7) to both
rsvd_bits_mask[0][2] and rsvd_bits_mask[1][2], if 1GB pages are not
supported.
As written, the patch has no effect on PDPTEs because
rsvd_bits_mask[0][2] is only accessed if bit 7 is zero.
Nadav, would you mind preparing a follow-up? Also, how did you find
these issues and test the fixes?
Paolo
next prev parent reply other threads:[~2014-04-28 10:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-04 3:31 [PATCH] KVM: x86: Fix page-tables reserved bits Nadav Amit
2014-04-16 19:03 ` Marcelo Tosatti
2014-04-16 21:17 ` H. Peter Anvin
2014-04-16 22:04 ` Marcelo Tosatti
2014-04-28 10:41 ` Paolo Bonzini [this message]
2014-04-28 12:20 ` Nadav Amit
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