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From: Oliver Upton To: Shameer Kolothum Cc: kvmarm@lists.linux.dev, maz@kernel.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, cohuck@redhat.com, eric.auger@redhat.com, sebott@redhat.com, yuzenghui@huawei.com, wangzhou1@hisilicon.com, jiangkunkun@huawei.com, jonathan.cameron@huawei.com, anthony.jebson@huawei.com, linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com Subject: Re: [PATCH v6 3/4] KVM: arm64: Report all the KVM/arm64-specific hypercalls Message-ID: References: <20250205132222.55816-1-shameerali.kolothum.thodi@huawei.com> <20250205132222.55816-4-shameerali.kolothum.thodi@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250205132222.55816-4-shameerali.kolothum.thodi@huawei.com> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250207_182116_638869_F4E663D9 X-CRM114-Status: GOOD ( 15.90 ) 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 Wed, Feb 05, 2025 at 01:22:21PM +0000, Shameer Kolothum wrote: > Currently ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID returns the > bitmap corresponding to KVM_REG_ARM_VENDOR_HYP_BMAP and it only > returns _KVM_FEATURES_FUNC_ID and _KVM_PTP_FUNC_ID. Change that > to return all the KVM/arm64-specific hypercalls exposed by > KVM/arm64 to guest operating systems. > > Signed-off-by: Shameer Kolothum > --- > arch/arm64/kvm/hypercalls.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c > index 27ce4cb44904..5cef2590ffdf 100644 > --- a/arch/arm64/kvm/hypercalls.c > +++ b/arch/arm64/kvm/hypercalls.c > @@ -359,7 +359,11 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu) > val[3] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3; > break; > case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID: > - val[0] = smccc_feat->vendor_hyp_bmap; > + val[0] = GENMASK(ARM_SMCCC_KVM_FUNC_PTP, > + ARM_SMCCC_KVM_FUNC_FEATURES); > + /* Function numbers 2-63 are reserved for pKVM for now */ > + val[2] = GENMASK((ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_CPUS - 64), > + (ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_VER - 64)); > break; This isn't right, vendor_hyp_bmap is very much load bearing. We have a documented UAPI that allows userspace to control the hypercalls exposed to the guest. The idea being a user wants kernel rollback safety and doesn't expose hypercalls that could potentially be revoked. https://docs.kernel.org/virt/kvm/arm/fw-pseudo-registers.html#bitmap-feature-firmware-registers -- Thanks, Oliver