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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id k85-20020a628458000000b0057725613627sm4955021pfd.142.2022.12.07.16.24.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Dec 2022 16:24:23 -0800 (PST) Date: Thu, 8 Dec 2022 00:24:20 +0000 From: Sean Christopherson To: Oliver Upton Cc: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Paolo Bonzini , Shuah Khan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kvmarm@lists.linux.dev, Ricardo Koller , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] KVM: selftests: Setup ucall after loading program into guest memory Message-ID: References: <20221207214809.489070-1-oliver.upton@linux.dev> <20221207214809.489070-3-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221207_162426_719265_CE39ED5D X-CRM114-Status: GOOD ( 23.34 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Dec 08, 2022, Oliver Upton wrote: > On Wed, Dec 07, 2022 at 11:57:27PM +0000, Sean Christopherson wrote: > > > diff --git a/tools/testing/selftests/kvm/aarch64/page_fault_test.c b/tools/testing/selftests/kvm/aarch64/page_fault_test.c > > > index 92d3a91153b6..95d22cfb7b41 100644 > > > --- a/tools/testing/selftests/kvm/aarch64/page_fault_test.c > > > +++ b/tools/testing/selftests/kvm/aarch64/page_fault_test.c > > > @@ -609,8 +609,13 @@ static void setup_memslots(struct kvm_vm *vm, struct test_params *p) > > > data_size / guest_page_size, > > > p->test_desc->data_memslot_flags); > > > vm->memslots[MEM_REGION_TEST_DATA] = TEST_DATA_MEMSLOT; > > > +} > > > + > > > +static void setup_ucall(struct kvm_vm *vm) > > > +{ > > > + struct userspace_mem_region *region = vm_get_mem_region(vm, MEM_REGION_TEST_DATA); > > > > > > - ucall_init(vm, data_gpa + data_size); > > > + ucall_init(vm, region->region.guest_phys_addr + region->region.memory_size); > > > > Isn't there a hole after CODE_AND_DATA_MEMSLOT? I.e. after memslot 0? > > Sure, but that's only guaranteed in the PA space. > > > The reason > > I ask is because if so, then we can do the temporarily heinous, but hopefully forward > > looking thing of adding a helper to wrap kvm_vm_elf_load() + ucall_init(). > > > > E.g. I think we can do this immediately, and then at some point in the 6.2 cycle > > add a dedicated region+memslot for the ucall MMIO page. > > Even still, that's just a kludge to make ucalls work. We have other > MMIO devices (GIC distributor, for example) that work by chance since > nothing conflicts with the constant GPAs we've selected in the tests. > > I'd rather we go down the route of having an address allocator for the > for both the VA and PA spaces to provide carveouts at runtime. Aren't those two separate issues? The PA, a.k.a. memslots space, can be solved by allocating a dedicated memslot, i.e. doesn't need a carve. At worst, collisions will yield very explicit asserts, which IMO is better than whatever might go wrong with a carve out. > There's another issue with the new ucall implementation where identity > mapping could stomp on a program segment that I'm fighting with right now > which only further highlights the problems with our (mis)management of > address spaces in selftests. Oooh, this crud: virt_pg_map(vm, mmio_gpa, mmio_gpa); Yeah, that needs to be fixed. But again, that's a separate issue, e.g. selftests can allocate a virtual address and map the read-only memslot. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel