On Tue, Apr 28, 2020 at 05:57:59PM +0200, Laurent Vivier wrote: > On 12/12/2018 05:17, Paul Mackerras wrote: > > + if (change == KVM_MR_FLAGS_ONLY && kvm_is_radix(kvm) && > > + ((new->flags ^ old->flags) & KVM_MEM_LOG_DIRTY_PAGES)) > > + kvmppc_radix_flush_memslot(kvm, old); > > } > > Hi, > > this part introduces a regression in QEMU test suite. > > We have the following warning in the host kernel log: > [snip] > > The problem is detected with the "migration-test" test program in qemu, > on a POWER9 host in radix mode with THP. It happens only the first time > the test program is run after loading kvm_hv. The warning is an explicit > detection [1] of a problem: Yes, we found a valid PTE where we didn't expect there to be one. [snip] > I reproduce the problem in QEMU 4.2 build directory with : > > sudo rmmod kvm_hv > sudo modprobe kvm_hv > make check-qtest-ppc64 > > or once the test binary is built with > > sudo rmmod kvm_hv > sudo modprobe kvm_hv > export QTEST_QEMU_BINARY=ppc64-softmmu/qemu-system-ppc64 > tests/qtest/migration-test > > The sub-test is "/migration/validate_uuid_error" that generates some > memory stress with a SLOF program in the source guest and fails because > of a mismatch with the destination guest. So the source guest continues > to execute the stress program while the migration is aborted. > > Another way to reproduce the problem is: > > Source guest: > > sudo rmmod kvm-hv > sudo modprobe kvm-hv > qemu-system-ppc64 -display none -accel kvm -name source -m 256M \ > -nodefaults -prom-env use-nvramrc?=true \ > -prom-env 'nvramrc=hex ." _" begin 6400000 100000 \ > do i c@ 1 + i c! 1000 +loop ." B" 0 until' -monitor \ > stdio > > Destination guest (on the same host): > > qemu-system-ppc64 -display none -accel kvm -name source -m 512M \ > -nodefaults -monitor stdio -incoming tcp:0:4444 > > Then in source guest monitor: > > (qemu) migrate tcp:localhost:4444 > > The migration intentionally fails because of a memory size mismatch and > the warning is generated in the host kernel log. I built QEMU 4.2 and tried all three methods you list without seeing the problem manifest itself. Is there any other configuration regarding THP or anything necessary? I was using the patch below, which you could try also, since you are better able to trigger the problem. I never saw the "flush_memslot was necessary" message nor the WARN_ON. If you see the flush_memslot message then that will give us a clue as to where the problem is coming from. Regards, Paul. -- diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h index 506e4df2d730..14ddf1411279 100644 --- a/arch/powerpc/include/asm/kvm_book3s.h +++ b/arch/powerpc/include/asm/kvm_book3s.h @@ -220,7 +220,7 @@ extern int kvm_test_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, unsigned long gfn); extern long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, unsigned long *map); -extern void kvmppc_radix_flush_memslot(struct kvm *kvm, +extern int kvmppc_radix_flush_memslot(struct kvm *kvm, const struct kvm_memory_slot *memslot); extern int kvmhv_get_rmmu_info(struct kvm *kvm, struct kvm_ppc_rmmu_info *info); diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index aa12cd4078b3..930042632d8f 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -433,7 +433,7 @@ static void kvmppc_unmap_free_pte(struct kvm *kvm, pte_t *pte, bool full, for (it = 0; it < PTRS_PER_PTE; ++it, ++p) { if (pte_val(*p) == 0) continue; - WARN_ON_ONCE(1); + WARN_ON(1); kvmppc_unmap_pte(kvm, p, pte_pfn(*p) << PAGE_SHIFT, PAGE_SHIFT, NULL, lpid); @@ -1092,30 +1092,34 @@ long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm, return 0; } -void kvmppc_radix_flush_memslot(struct kvm *kvm, +int kvmppc_radix_flush_memslot(struct kvm *kvm, const struct kvm_memory_slot *memslot) { unsigned long n; pte_t *ptep; unsigned long gpa; unsigned int shift; + int ret = 0; if (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START) kvmppc_uvmem_drop_pages(memslot, kvm, true); if (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE) - return; + return 0; gpa = memslot->base_gfn << PAGE_SHIFT; spin_lock(&kvm->mmu_lock); for (n = memslot->npages; n; --n) { ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); - if (ptep && pte_present(*ptep)) + if (ptep && pte_present(*ptep)) { kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot, kvm->arch.lpid); + ret = 1; + } gpa += PAGE_SIZE; } spin_unlock(&kvm->mmu_lock); + return ret; } static void add_rmmu_ap_encoding(struct kvm_ppc_rmmu_info *info, diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 93493f0cbfe8..40b50f867835 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4508,6 +4508,10 @@ static void kvmppc_core_commit_memory_region_hv(struct kvm *kvm, if (change == KVM_MR_FLAGS_ONLY && kvm_is_radix(kvm) && ((new->flags ^ old->flags) & KVM_MEM_LOG_DIRTY_PAGES)) kvmppc_radix_flush_memslot(kvm, old); + else if (kvm_is_radix(kvm) && kvmppc_radix_flush_memslot(kvm, old)) + pr_err("flush_memslot was necessary - change = %d flags %x -> %x\n", + change, old->flags, new->flags); + /* * If UV hasn't yet called H_SVM_INIT_START, don't register memslots. */