From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Sean Christopherson <sean.j.christopherson@intel.com>,
Marc Zyngier <Marc.Zyngier@arm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>
Subject: Re: [PATCH v4 30/30] KVM: selftests: Add test to populate a VM with the max possible guest mem
Date: Tue, 8 Mar 2022 16:36:31 +0100 [thread overview]
Message-ID: <b64c2540-be37-0b03-a216-39b4eb5ef85c@de.ibm.com> (raw)
In-Reply-To: <63f4a488-87f1-097f-95d5-f85e46786740@redhat.com>
Am 08.03.22 um 15:47 schrieb Paolo Bonzini:
> On 3/3/22 20:38, Paolo Bonzini wrote:
>> From: Sean Christopherson<seanjc@google.com>
>>
>> Add a selftest that enables populating a VM with the maximum amount of
>> guest memory allowed by the underlying architecture. Abuse KVM's
>> memslots by mapping a single host memory region into multiple memslots so
>> that the selftest doesn't require a system with terabytes of RAM.
>>
>> Default to 512gb of guest memory, which isn't all that interesting, but
>> should work on all MMUs and doesn't take an exorbitant amount of memory
>> or time. E.g. testing with ~64tb of guest memory takes the better part
>> of an hour, and requires 200gb of memory for KVM's page tables when using
>> 4kb pages.
>
> I couldn't quite run this on a laptop, so I'll tune it down to 128gb and 3/4 of the available CPUs.
>
>> To inflicit maximum abuse on KVM' MMU, default to 4kb pages (or whatever
>> the not-hugepage size is) in the backing store (memfd). Use memfd for
>> the host backing store to ensure that hugepages are guaranteed when
>> requested, and to give the user explicit control of the size of hugepage
>> being tested.
>>
>> By default, spin up as many vCPUs as there are available to the selftest,
>> and distribute the work of dirtying each 4kb chunk of memory across all
>> vCPUs. Dirtying guest memory forces KVM to populate its page tables, and
>> also forces KVM to write back accessed/dirty information to struct page
>> when the guest memory is freed.
>>
>> On x86, perform two passes with a MMU context reset between each pass to
>> coerce KVM into dropping all references to the MMU root, e.g. to emulate
>> a vCPU dropping the last reference. Perform both passes and all
>> rendezvous on all architectures in the hope that arm64 and s390x can gain
>> similar shenanigans in the future.
>
> Did you actually test aarch64 (not even asking about s390 :))? For now let's only add it for x86.
I do get spurious
# selftests: kvm: max_guest_memory_test
# ==== Test Assertion Failure ====
# lib/kvm_util.c:883: !ret
# pid=575178 tid=575178 errno=22 - Invalid argument
# 1 0x000000000100385f: vm_set_user_memory_region at kvm_util.c:883
# 2 0x0000000001001ee1: main at max_guest_memory_test.c:242
# 3 0x000003ffa1033731: ?? ??:0
# 4 0x000003ffa103380d: ?? ??:0
# 5 0x0000000001002389: _start at ??:?
# KVM_SET_USER_MEMORY_REGION failed, errno = 22 (Invalid argument)
not ok 9 selftests: kvm: max_guest_memory_test # exit=254
as the userspace address must be 1MB-aligned but the mmap is not (due to aslr).
There are probably more issues, so it certainly is ok to skip s390 for now.
>
>> + TEST_ASSERT(nr_vcpus, "#DE");
>
> srsly? :)
>
> Paolo
>
next prev parent reply other threads:[~2022-03-08 15:37 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-03 19:38 [PATCH v4 00/30] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 01/30] KVM: x86/mmu: Check for present SPTE when clearing dirty bit in TDP MMU Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 02/30] KVM: x86/mmu: Fix wrong/misleading comments in TDP MMU fast zap Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 03/30] KVM: x86/mmu: Formalize TDP MMU's (unintended?) deferred TLB flush logic Paolo Bonzini
2022-03-03 23:39 ` Mingwei Zhang
2022-03-03 19:38 ` [PATCH v4 04/30] KVM: x86/mmu: Document that zapping invalidated roots doesn't need to flush Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 05/30] KVM: x86/mmu: Require mmu_lock be held for write in unyielding root iter Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 06/30] KVM: x86/mmu: only perform eager page splitting on valid roots Paolo Bonzini
2022-03-03 20:03 ` Sean Christopherson
2022-03-03 19:38 ` [PATCH v4 07/30] KVM: x86/mmu: do not allow readers to acquire references to invalid roots Paolo Bonzini
2022-03-03 20:12 ` Sean Christopherson
2022-03-03 19:38 ` [PATCH v4 08/30] KVM: x86/mmu: Check for !leaf=>leaf, not PFN change, in TDP MMU SP removal Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 09/30] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 10/30] KVM: x86/mmu: Drop RCU after processing each root in MMU notifier hooks Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 11/30] KVM: x86/mmu: Add helpers to read/write TDP MMU SPTEs and document RCU Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 12/30] KVM: x86/mmu: WARN if old _or_ new SPTE is REMOVED in non-atomic path Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 13/30] KVM: x86/mmu: Refactor low-level TDP MMU set SPTE helper to take raw values Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 14/30] KVM: x86/mmu: Zap only the target TDP MMU shadow page in NX recovery Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 15/30] KVM: x86/mmu: Skip remote TLB flush when zapping all of TDP MMU Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 16/30] KVM: x86/mmu: Add dedicated helper to zap TDP MMU root shadow page Paolo Bonzini
2022-03-04 0:07 ` Mingwei Zhang
2022-03-03 19:38 ` [PATCH v4 17/30] KVM: x86/mmu: Require mmu_lock be held for write to zap TDP MMU range Paolo Bonzini
2022-03-04 0:14 ` Mingwei Zhang
2022-03-03 19:38 ` [PATCH v4 18/30] KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range() Paolo Bonzini
2022-03-04 1:16 ` Mingwei Zhang
2022-03-04 16:11 ` Sean Christopherson
2022-03-04 18:00 ` Mingwei Zhang
2022-03-04 18:42 ` Sean Christopherson
2022-03-11 15:09 ` Vitaly Kuznetsov
2022-03-13 18:40 ` Mingwei Zhang
2022-03-25 15:13 ` Sean Christopherson
2022-03-26 18:10 ` Mingwei Zhang
2022-03-28 15:06 ` Sean Christopherson
2022-03-03 19:38 ` [PATCH v4 19/30] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched Paolo Bonzini
2022-03-04 1:19 ` Mingwei Zhang
2022-03-03 19:38 ` [PATCH v4 20/30] KVM: x86/mmu: Defer TLB flush to caller when freeing TDP MMU shadow pages Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 21/30] KVM: x86/mmu: Zap invalidated roots via asynchronous worker Paolo Bonzini
2022-03-03 20:54 ` Sean Christopherson
2022-03-03 21:06 ` Sean Christopherson
2022-03-03 21:20 ` Sean Christopherson
2022-03-03 21:32 ` Sean Christopherson
2022-03-04 6:48 ` Paolo Bonzini
2022-03-04 16:02 ` Sean Christopherson
2022-03-04 18:11 ` Paolo Bonzini
2022-03-05 0:34 ` Sean Christopherson
2022-03-05 19:53 ` Paolo Bonzini
2022-03-08 21:29 ` Sean Christopherson
2022-03-11 17:50 ` Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 22/30] KVM: x86/mmu: Allow yielding when zapping GFNs for defunct TDP MMU root Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 23/30] KVM: x86/mmu: Zap roots in two passes to avoid inducing RCU stalls Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 24/30] KVM: x86/mmu: Zap defunct roots via asynchronous worker Paolo Bonzini
2022-03-03 22:08 ` Sean Christopherson
2022-03-03 19:38 ` [PATCH v4 25/30] KVM: x86/mmu: Check for a REMOVED leaf SPTE before making the SPTE Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 26/30] KVM: x86/mmu: WARN on any attempt to atomically update REMOVED SPTE Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 27/30] KVM: selftests: Move raw KVM_SET_USER_MEMORY_REGION helper to utils Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 28/30] KVM: selftests: Split out helper to allocate guest mem via memfd Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 29/30] KVM: selftests: Define cpu_relax() helpers for s390 and x86 Paolo Bonzini
2022-03-03 19:38 ` [PATCH v4 30/30] KVM: selftests: Add test to populate a VM with the max possible guest mem Paolo Bonzini
2022-03-08 14:47 ` Paolo Bonzini
2022-03-08 15:36 ` Christian Borntraeger [this message]
2022-03-08 21:09 ` Sean Christopherson
2022-03-08 17:25 ` [PATCH v4 00/30] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b64c2540-be37-0b03-a216-39b4eb5ef85c@de.ibm.com \
--to=borntraeger@de.ibm.com \
--cc=Marc.Zyngier@arm.com \
--cc=frankja@linux.ibm.com \
--cc=imbrenda@linux.ibm.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=sean.j.christopherson@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).