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[35.233.69.230]) by smtp.gmail.com with ESMTPSA id j30sm28608530wrj.62.2021.03.17.07.47.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Mar 2021 07:47:27 -0700 (PDT) Date: Wed, 17 Mar 2021 14:47:25 +0000 From: Quentin Perret To: Marc Zyngier Cc: catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, android-kvm@google.com, seanjc@google.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, tabba@google.com, ardb@kernel.org, mark.rutland@arm.com, dbrazdil@google.com, mate.toth-pal@arm.com Subject: Re: [PATCH 1/2] KVM: arm64: Introduce KVM_PGTABLE_S2_NOFWB Stage-2 flag Message-ID: References: <20210315143536.214621-34-qperret@google.com> <20210317141714.383046-1-qperret@google.com> <20210317141714.383046-2-qperret@google.com> <87a6r1j10k.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87a6r1j10k.wl-maz@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 17 Mar 2021 at 14:41:31 (+0000), Marc Zyngier wrote: > Hi Quentin, > > On Wed, 17 Mar 2021 14:17:13 +0000, > Quentin Perret wrote: > > > > In order to further configure stage-2 page-tables, pass flags to the > > init function using a new enum. > > > > The first of these flags allows to disable FWB even if the hardware > > supports it as we will need to do so for the host stage-2. > > > > Signed-off-by: Quentin Perret > > > > --- > > > > One question is, do we want to use stage2_has_fwb() everywhere, including > > guest-specific paths (e.g. kvm_arch_prepare_memory_region(), ...) ? > > > > That'd make this patch more intrusive, but would make the whole codebase > > work with FWB enabled on a guest by guest basis. I don't see us use that > > anytime soon (other than maybe debug of some sort?) but it'd be good to > > have an agreement. > > I'm not sure how useful that would be. We fought long and hard to get > FWB, and I can't see a good reason to disable it for guests unless the > HW was buggy (but in which case that'd be for everyone). I'd rather > keep the changes small for now (this whole series is invasive > enough!). OK, that works for me. > As for this patch, I only have a few cosmetic comments: Happy with the suggestions, I'll fold that in v6. Cheers, Quentin