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From: Oliver Upton To: Ricardo Koller Subject: Re: [RFC PATCH 01/12] KVM: arm64: Relax WARN check in stage2_make_pte() Message-ID: References: <20221112081714.2169495-1-ricarkol@google.com> <20221112081714.2169495-2-ricarkol@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20221112081714.2169495-2-ricarkol@google.com> X-Migadu-Flow: FLOW_OUT Cc: ricarkol@gmail.com, kvm@vger.kernel.org, catalin.marinas@arm.com, kvmarm@lists.linux.dev, andrew.jones@linux.dev, bgardon@google.com, maz@kernel.org, dmatlack@google.com, pbonzini@redhat.com, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Ricardo, On Sat, Nov 12, 2022 at 08:17:03AM +0000, Ricardo Koller wrote: > stage2_make_pte() throws a warning when used in a non-shared walk, as PTEs > are not "locked" when walking non-shared. Add a check so it can be used > non-shared. > > Signed-off-by: Ricardo Koller I would very much prefer to leave this WARN as-is. Correct me if I am wrong, but I do not believe this warning is firing with the existing code. While the locking portion doesn't make a whole lot of sense for a non-shared walk, it is also a magic value that indicates we've already done the break side of break-before-make. If the warning fires then that would suggest our break-before-make implementation isn't working as expected. -- Thanks, Oliver > --- > arch/arm64/kvm/hyp/pgtable.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index c12462439e70..b16107bf917c 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -733,7 +733,8 @@ static void stage2_make_pte(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t n > { > struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; > > - WARN_ON(!stage2_pte_is_locked(*ctx->ptep)); > + if (kvm_pgtable_walk_shared(ctx)) > + WARN_ON(!stage2_pte_is_locked(*ctx->ptep)); > > if (stage2_pte_is_counted(new)) > mm_ops->get_page(ctx->ptep); > -- > 2.38.1.431.g37b22c650d-goog > > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A21678485 for ; Mon, 14 Nov 2022 20:59:24 +0000 (UTC) Date: Mon, 14 Nov 2022 20:59:13 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1668459563; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hGeByEF7fiPw7L8RkZy6v3SdTEQDaiCEVE4F9gxaZWU=; b=QZGj0VnKfsWs4mmYs5F8K2KzfTrFTlQ11QyOmE6mpMfbFQzlOQCUkNNYmyJ+tD7/0LR3Nk VwtMk3HwDmV2fJNzQWGHVnZ6ULtAPfFfWVkHX60MD8aEUxv/aJMhqGhgWY+u2IADU8ax1k ZbR1yeBw8FU3uOrTPeENLsM5XOYKJNQ= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Ricardo Koller Cc: pbonzini@redhat.com, maz@kernel.org, dmatlack@google.com, qperret@google.com, catalin.marinas@arm.com, andrew.jones@linux.dev, seanjc@google.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, eric.auger@redhat.com, gshan@redhat.com, reijiw@google.com, rananta@google.com, bgardon@google.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, ricarkol@gmail.com Subject: Re: [RFC PATCH 01/12] KVM: arm64: Relax WARN check in stage2_make_pte() Message-ID: References: <20221112081714.2169495-1-ricarkol@google.com> <20221112081714.2169495-2-ricarkol@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221112081714.2169495-2-ricarkol@google.com> X-Migadu-Flow: FLOW_OUT Message-ID: <20221114205913.xD1o5G7ixh4xKXow8rGJHKWNLu56vx_eTtJLqU1V5gA@z> Hi Ricardo, On Sat, Nov 12, 2022 at 08:17:03AM +0000, Ricardo Koller wrote: > stage2_make_pte() throws a warning when used in a non-shared walk, as PTEs > are not "locked" when walking non-shared. Add a check so it can be used > non-shared. > > Signed-off-by: Ricardo Koller I would very much prefer to leave this WARN as-is. Correct me if I am wrong, but I do not believe this warning is firing with the existing code. While the locking portion doesn't make a whole lot of sense for a non-shared walk, it is also a magic value that indicates we've already done the break side of break-before-make. If the warning fires then that would suggest our break-before-make implementation isn't working as expected. -- Thanks, Oliver > --- > arch/arm64/kvm/hyp/pgtable.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index c12462439e70..b16107bf917c 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -733,7 +733,8 @@ static void stage2_make_pte(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t n > { > struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; > > - WARN_ON(!stage2_pte_is_locked(*ctx->ptep)); > + if (kvm_pgtable_walk_shared(ctx)) > + WARN_ON(!stage2_pte_is_locked(*ctx->ptep)); > > if (stage2_pte_is_counted(new)) > mm_ops->get_page(ctx->ptep); > -- > 2.38.1.431.g37b22c650d-goog > >