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[88.115.161.74]) by smtp.gmail.com with ESMTPSA id g22-20020ac25396000000b004cb14fa604csm1680397lfh.262.2023.03.06.07.37.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Mar 2023 07:37:52 -0800 (PST) Date: Mon, 6 Mar 2023 17:37:51 +0200 From: Zhi Wang To: Steven Price Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev Subject: Re: [RFC PATCH 15/28] KVM: arm64: Handle realm MMIO emulation Message-ID: <20230306173751.000026d4@gmail.com> In-Reply-To: <20230127112932.38045-16-steven.price@arm.com> References: <20230127112248.136810-1-suzuki.poulose@arm.com> <20230127112932.38045-1-steven.price@arm.com> <20230127112932.38045-16-steven.price@arm.com> X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 27 Jan 2023 11:29:19 +0000 Steven Price wrote: > MMIO emulation for a realm cannot be done directly with the VM's > registers as they are protected from the host. However the RMM interface > provides a structure member for providing the read/written value and More details would be better for helping the review. I can only see the emulated mmio value from the device model (kvmtool or kvm_io_bus) is put into the GPRS[0] of the RecEntry object. But the rest of the flow is missing. I guess RMM copies the value in the RecEntry.GPRS[0] to the target GPR in the guest context in RMI_REC_ENTER when seeing RMI_EMULATED_MMIO. This is for the guest MMIO read path. How about the MMIO write path? I don't see where the RecExit.GPRS[0] is loaded to a varible and returned to the userspace. > we can transfer this to the appropriate VCPU's register entry and then > depend on the generic MMIO handling code in KVM. > > Signed-off-by: Steven Price > --- > arch/arm64/kvm/mmio.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c > index 3dd38a151d2a..c4879fa3a8d3 100644 > --- a/arch/arm64/kvm/mmio.c > +++ b/arch/arm64/kvm/mmio.c > @@ -6,6 +6,7 @@ > > #include > #include > +#include > #include > > #include "trace.h" > @@ -109,6 +110,9 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu) > &data); > data = vcpu_data_host_to_guest(vcpu, data, len); > vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data); > + > + if (vcpu_is_rec(vcpu)) > + vcpu->arch.rec.run->entry.gprs[0] = data; I think the guest context is maintained by RMM (while KVM can only touch Rec{Entry, Exit} object) so that guest context in the legacy VHE mode is unused. If yes, I guess here is should be: if (unlikely(vcpu_is_rec(vcpu))) vcpu->arch.rec.run->entry.gprs[0] = data; else vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data); > } > > /* > @@ -179,6 +183,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa) > run->mmio.len = len; > vcpu->mmio_needed = 1; > > + if (vcpu_is_rec(vcpu)) > + vcpu->arch.rec.run->entry.flags |= RMI_EMULATED_MMIO; > + Wouldn't it be better to set this in the kvm_handle_mmio_return where the MMIO read emulation has been surely successful? > if (!ret) { > /* We handled the access successfully in the kernel. */ > if (!is_write)