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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "James Hogan" <jhogan@kernel.org>,
	"Paul Mackerras" <paulus@ozlabs.org>,
	"Janosch Frank" <frankja@linux.ibm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Marc Zyngier" <maz@kernel.org>,
	"David Hildenbrand" <david@redhat.com>,
	"Cornelia Huck" <cohuck@redhat.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"James Morse" <james.morse@arm.com>,
	"Julien Thierry" <julien.thierry.kdev@gmail.com>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
	"Christoffer Dall" <christoffer.dall@arm.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>
Subject: Re: [PATCH v4 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION
Date: Tue, 24 Mar 2020 10:43:07 +0100
Message-ID: <78b21097-52e4-b851-fc78-da3442fd0904@de.ibm.com> (raw)
In-Reply-To: <20191218163958.GC25201@linux.intel.com>



On 18.12.19 17:39, Sean Christopherson wrote:
> On Wed, Dec 18, 2019 at 12:39:43PM +0100, Christian Borntraeger wrote:
>>
>> On 17.12.19 21:40, Sean Christopherson wrote:
>>> Add a KVM selftest to test moving the base gfn of a userspace memory
>>> region.  The test is primarily targeted at x86 to verify its memslot
>>> metadata is correctly updated, but also provides basic functionality
>>> coverage on other architectures.
>>> +static void *vcpu_worker(void *data)
>>> +{
>>> +	struct kvm_vm *vm = data;
>>> +	struct kvm_run *run;
>>> +	struct ucall uc;
>>> +	uint64_t cmd;
>>> +
>>> +	/*
>>> +	 * Loop until the guest is done.  Re-enter the guest on all MMIO exits,
>>> +	 * which will occur if the guest attempts to access a memslot while it
>>> +	 * is being moved.
>>> +	 */
>>> +	run = vcpu_state(vm, VCPU_ID);
>>> +	do {
>>> +		vcpu_run(vm, VCPU_ID);
>>> +	} while (run->exit_reason == KVM_EXIT_MMIO);
>>> +
>>> +	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
>>> +		    "Unexpected exit reason = %d", run->exit_reason);
>>
>>
>> This will also not work for s390. Maybe just make this test x86 specific for now?
> 
> Doh, that's obvious in hindsight.  I think the basic premise is also
> broken on arm64 as it returns -EFAULT on is_error_noslot_pfn(pfn).  So
> yeah, x86 only for now :-(

I started looking into this what it would cost to implement this on s390.
s390 is also returning EFAULT if no memory slot is available.

According to the doc this is not documented at all. So this part of the test
        vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
        vm_vcpu_add(vm, VCPU_ID);
        /* Fails with ENOSPC because the MMU can't create pages (no slots). */
        TEST_ASSERT(_vcpu_run(vm, VCPU_ID) == -1 && errno == ENOSPC,
                    "Unexpected error code = %d", errno);
        kvm_vm_free(vm);

is actually just testing that the implementation for x86 does not change the error
from ENOSPC to something else.

The question is: do we want to document the error for the "no memslot" case and then
change all existing platforms?


  reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 20:40 [PATCH v4 00/19] KVM: Dynamically size memslot arrays Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Sean Christopherson
2019-12-17 20:48   ` Sean Christopherson
2019-12-17 20:50     ` Sean Christopherson
2019-12-17 21:56   ` Peter Xu
2019-12-17 22:20     ` Sean Christopherson
2019-12-17 22:37       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 02/19] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 03/19] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 04/19] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 05/19] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-12-17 22:07   ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 06/19] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 07/19] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-12-17 22:24   ` Peter Xu
2019-12-17 22:51     ` Sean Christopherson
2019-12-18 16:17       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 08/19] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 09/19] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 10/19] KVM: Drop "const" attribute from old memslot in commit_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 11/19] KVM: x86: Free arrays for old memslot when moving memslot's base gfn Sean Christopherson
2019-12-17 22:48   ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 12/19] KVM: Move memslot deletion to helper function Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 13/19] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 14/19] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 15/19] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 16/19] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-12-24 18:19   ` Peter Xu
2020-01-14 18:25     ` Sean Christopherson
2020-02-06 22:03       ` Peter Xu
2020-02-07 18:52         ` Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 17/19] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 18/19] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION Sean Christopherson
2019-12-18 11:29   ` Christian Borntraeger
2019-12-18 11:39   ` Christian Borntraeger
2019-12-18 16:39     ` Sean Christopherson
2020-03-24  9:43       ` Christian Borntraeger [this message]
2020-03-24 18:20         ` Sean Christopherson
2019-12-18 11:40 ` [PATCH v4 00/19] KVM: Dynamically size memslot arrays Christian Borntraeger
2019-12-18 18:10 ` Marc Zyngier

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