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From: Ben Gardon <bgardon@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-kselftest@vger.kernel.org,
	Cannon Matthews <cannonmatthews@google.com>,
	Peter Xu <peterx@redhat.com>, Andrew Jones <drjones@redhat.com>,
	Peter Shier <pshier@google.com>, Oliver Upton <oupton@google.com>
Subject: Re: [PATCH v4 09/10] KVM: selftests: Stop memslot creation in KVM internal memslot region
Date: Fri, 24 Jan 2020 10:41:55 -0800
Message-ID: <CANgfPd8jpUykwrOnToXx+zhJOJvnWvxhZPSKhAwST=wwYdtA3A@mail.gmail.com> (raw)
In-Reply-To: <92042648-e43a-d996-dc38-aded106b976b@redhat.com>

On Fri, Jan 24, 2020 at 12:58 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 23/01/20 19:04, Ben Gardon wrote:
> > KVM creates internal memslots covering the region between 3G and 4G in
> > the guest physical address space, when the first vCPU is created.
> > Mapping this region before creation of the first vCPU causes vCPU
> > creation to fail. Prohibit tests from creating such a memslot and fail
> > with a helpful warning when they try to.
> >
> > Signed-off-by: Ben Gardon <bgardon@google.com>
> > ---
>
> The internal memslots are much higher than this (0xfffbc000 and
> 0xfee00000).  I'm changing the patch to block 0xfe0000000 and above,
> otherwise it breaks vmx_dirty_log_test.

Perhaps we're working in different units, but I believe paddrs
0xfffbc000 and 0xfee00000 are between 3GiB and 4GiB.
"Proof by Python":
>>> B=1
>>> KB=1024*B
>>> MB=1024*KB
>>> GB=1024*MB
>>> hex(3*GB)
'0xc0000000'
>>> hex(4*GB)
'0x100000000'
>>> 3*GB == 3<<30
True
>>> 0xfffbc000 > 3*GB
True
>>> 0xfffbc000 < 4*GB
True
>>> 0xfee00000 > 3*GB
True
>>> 0xfee00000 < 4*GB
True

Am I missing something?

I don't think blocking 0xfe0000000 and above is useful, as there's
nothing mapped in that region and AFAIK it's perfectly valid to create
memslots there.


>
> Paolo
>

  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 18:04 [PATCH v4 00/10] Create a userfaultfd demand paging test Ben Gardon
2020-01-23 18:04 ` [PATCH v4 01/10] KVM: selftests: Create a " Ben Gardon
2020-01-24  9:49   ` Andrew Jones
2020-01-27  9:18   ` Thomas Huth
2020-01-23 18:04 ` [PATCH v4 02/10] KVM: selftests: Add demand paging content to the " Ben Gardon
2020-01-23 18:04 ` [PATCH v4 03/10] KVM: selftests: Add configurable demand paging delay Ben Gardon
2020-01-23 18:04 ` [PATCH v4 04/10] KVM: selftests: Add memory size parameter to the demand paging test Ben Gardon
2020-01-24 10:01   ` Andrew Jones
2020-01-23 18:04 ` [PATCH v4 05/10] KVM: selftests: Pass args to vCPU in global vCPU args struct Ben Gardon
2020-01-23 18:04 ` [PATCH v4 06/10] KVM: selftests: Add support for vcpu_args_set to aarch64 and s390x Ben Gardon
2020-01-24  9:03   ` Paolo Bonzini
2020-01-24  9:35     ` Andrew Jones
2020-01-24  9:44       ` Paolo Bonzini
2020-01-24 10:45       ` Andrew Jones
2020-01-24 18:33     ` Christian Borntraeger
2020-01-25  9:34   ` Paolo Bonzini
2020-01-27  8:38     ` Andrew Jones
2020-01-27  9:01   ` Thomas Huth
2020-01-23 18:04 ` [PATCH v4 07/10] KVM: selftests: Support multiple vCPUs in demand paging test Ben Gardon
2020-01-24 10:16   ` Andrew Jones
2020-01-24 10:49   ` Andrew Jones
2020-01-25  9:39     ` Paolo Bonzini
2020-01-27  8:39       ` Andrew Jones
2020-01-23 18:04 ` [PATCH v4 08/10] KVM: selftests: Time guest demand paging Ben Gardon
2020-01-24 10:21   ` Andrew Jones
2020-01-23 18:04 ` [PATCH v4 09/10] KVM: selftests: Stop memslot creation in KVM internal memslot region Ben Gardon
2020-01-24  8:58   ` Paolo Bonzini
2020-01-24 18:41     ` Ben Gardon [this message]
2020-01-25  9:37       ` Paolo Bonzini
2020-01-27 17:28         ` Ben Gardon
2020-01-23 18:04 ` [PATCH v4 10/10] KVM: selftests: Move memslot 0 above KVM internal memslots Ben Gardon
2020-01-24  9:01   ` Paolo Bonzini
2020-01-24 18:53     ` Ben Gardon
2020-01-27  9:42   ` Thomas Huth
2020-01-24  9:03 ` [PATCH v4 00/10] Create a userfaultfd demand paging test Paolo Bonzini

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