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[104.155.91.135]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cee7fec25sm544179385e9.13.2026.09.08.03.07.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2026 03:07:16 -0700 (PDT) Date: Tue, 8 Sep 2026 11:07:12 +0100 From: Vincent Donnefort To: Wei-Lin Chang Cc: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kernel-team@android.com, fuad.tabba@linux.dev, qperret@google.com, keirf@google.com Subject: Re: [PATCH 02/20] KVM: arm64: Propagate host stage-2 annotated entries on block split Message-ID: References: <20260803100904.3563942-1-vdonnefort@google.com> <20260803100904.3563942-3-vdonnefort@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260908_030721_118631_C1D66044 X-CRM114-Status: GOOD ( 19.56 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 07, 2026 at 02:58:41PM +0100, Wei-Lin Chang wrote: > On Mon, Aug 03, 2026 at 11:08:46AM +0100, Vincent Donnefort wrote: > > [...] > > > static void stage2_map_prefault_idmap(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t *ptep) > > { > > kvm_pte_t block_pte = ctx->old; > > + bool counted, valid; > > u64 pa; > > int i; > > > > - if (!kvm_pte_valid(block_pte)) > > + counted = stage2_pte_is_counted(block_pte); > > + valid = kvm_pte_valid(block_pte); > > + > > + if (!valid && !counted) > > + return; > > + > > + /* > > + * Shared walks not supported: cannot rollback refcounts on break > > + * failure. > > + */ > > + if (counted && WARN_ON_ONCE(kvm_pgtable_walk_shared(ctx))) > > Doesn't patch 1 also need this shared walk check, Only the host stage-2 has the IDMAP flag and will run this function. For the host stage-2, only non valid PTEs and non-RWX PTEs are refcounted. * non-valid PTEs are skipped in PATCH 1. * non-RWX PTEs are forced PTE-level. So there's no risk of hitting a refcounted PTE in this function until PATCH 2. -- Vincent > > > return; > > > > pa = ALIGN_DOWN(ctx->addr, kvm_granule_size(ctx->level)); > > for (i = 0; i < PTRS_PER_PTE; ++i, ++ptep, pa += kvm_granule_size(ctx->level + 1)) { > > - kvm_pte_t pte = kvm_init_valid_leaf_pte(pa, block_pte, ctx->level + 1); > > + kvm_pte_t pte = valid ? > > + kvm_init_valid_leaf_pte(pa, block_pte, ctx->level + 1) : > > + block_pte; > > > > /* > > * Skip ptes in the range being modified by the caller if we're > > @@ -1053,8 +1066,11 @@ static void stage2_map_prefault_idmap(const struct kvm_pgtable_visit_ctx *ctx, k > > * that should happen very infrequently. > > */ > > if ((ctx->level < (KVM_PGTABLE_LAST_LEVEL - 1)) || > > - (pa < ctx->addr) || (pa >= ctx->end)) > > + (pa < ctx->addr) || (pa >= ctx->end)) { > > *ptep = pte; > > + if (counted) > > + ctx->mm_ops->get_page(ptep); > > and this get_page() ? > > Thanks, > Wei-Lin Chang > > [...]