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Wed, 08 Jan 2025 06:41:35 -0800 (PST) Date: Wed, 8 Jan 2025 06:41:34 -0800 In-Reply-To: X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Mime-Version: 1.0 References: <20250101064928.389504-1-pbonzini@redhat.com> Message-ID: Subject: Re: [PATCH] KVM: allow NULL writable argument to __kvm_faultin_pfn From: Sean Christopherson To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Christian Zigotzky , linuxppc-dev@lists.ozlabs.org, regressions@lists.linux.dev Content-Type: text/plain; charset="us-ascii" On Mon, Jan 06, 2025, Sean Christopherson wrote: > On Wed, Jan 01, 2025, Paolo Bonzini wrote: > > kvm_follow_pfn() is able to work with NULL in the .map_writable field > > of the homonymous struct. But __kvm_faultin_pfn() rejects the combo > > despite KVM for e500 trying to use it. Indeed .map_writable is not > > particularly useful if the flags include FOLL_WRITE and readonly > > guest memory is not supported, so add support to __kvm_faultin_pfn() > > for this case. > > I would prefer to keep the sanity check to minimize the risk of a page fault > handler not supporting opportunistic write mappings. e500 is definitely the > odd one out here. Per a quick chat at PUCK, Paolo is going to try and fix the e500 code to actually use the @writable param as it's intended.