From 05714cab7d63b189894235cf310fae7d6ffc2e9b Mon Sep 17 00:00:00 2001 From: Raghavendra Rao Ananta Date: Mon, 2 May 2022 23:38:46 +0000 Subject: KVM: arm64: Setup a framework for hypercall bitmap firmware registers KVM regularly introduces new hypercall services to the guests without any consent from the userspace. This means, the guests can observe hypercall services in and out as they migrate across various host kernel versions. This could be a major problem if the guest discovered a hypercall, started using it, and after getting migrated to an older kernel realizes that it's no longer available. Depending on how the guest handles the change, there's a potential chance that the guest would just panic. As a result, there's a need for the userspace to elect the services that it wishes the guest to discover. It can elect these services based on the kernels spread across its (migration) fleet. To remedy this, extend the existing firmware pseudo-registers, such as KVM_REG_ARM_PSCI_VERSION, but by creating a new COPROC register space for all the hypercall services available. These firmware registers are categorized based on the service call owners, but unlike the existing firmware pseudo-registers, they hold the features supported in the form of a bitmap. During the VM initialization, the registers are set to upper-limit of the features supported by the corresponding registers. It's expected that the VMMs discover the features provided by each register via GET_ONE_REG, and write back the desired values using SET_ONE_REG. KVM allows this modification only until the VM has started. Some of the standard features are not mapped to any bits of the registers. But since they can recreate the original problem of making it available without userspace's consent, they need to be explicitly added to the case-list in kvm_hvc_call_default_allowed(). Any function-id that's not enabled via the bitmap, or not listed in kvm_hvc_call_default_allowed, will be returned as SMCCC_RET_NOT_SUPPORTED to the guest. Older userspace code can simply ignore the feature and the hypercall services will be exposed unconditionally to the guests, thus ensuring backward compatibility. In this patch, the framework adds the register only for ARM's standard secure services (owner value 4). Currently, this includes support only for ARM True Random Number Generator (TRNG) service, with bit-0 of the register representing mandatory features of v1.0. Other services are momentarily added in the upcoming patches. Signed-off-by: Raghavendra Rao Ananta Reviewed-by: Gavin Shan [maz: reduced the scope of some helpers, tidy-up bitmap max values, dropped error-only fast path] Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220502233853.1233742-3-rananta@google.com --- arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'arch/arm64/include/asm/kvm_host.h') diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 94a27a7520f4..fef597af0beb 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -101,6 +101,15 @@ struct kvm_s2_mmu { struct kvm_arch_memory_slot { }; +/** + * struct kvm_smccc_features: Descriptor of the hypercall services exposed to the guests + * + * @std_bmap: Bitmap of standard secure service calls + */ +struct kvm_smccc_features { + unsigned long std_bmap; +}; + struct kvm_arch { struct kvm_s2_mmu mmu; @@ -150,6 +159,9 @@ struct kvm_arch { u8 pfr0_csv2; u8 pfr0_csv3; + + /* Hypercall features firmware registers' descriptor */ + struct kvm_smccc_features smccc_feat; }; struct kvm_vcpu_fault_info { -- cgit From 428fd6788d4d0e0d390de9fb4486be3c1187310d Mon Sep 17 00:00:00 2001 From: Raghavendra Rao Ananta Date: Mon, 2 May 2022 23:38:47 +0000 Subject: KVM: arm64: Add standard hypervisor firmware register Introduce the firmware register to hold the standard hypervisor service calls (owner value 5) as a bitmap. The bitmap represents the features that'll be enabled for the guest, as configured by the user-space. Currently, this includes support only for Paravirtualized time, represented by bit-0. Signed-off-by: Raghavendra Rao Ananta Reviewed-by: Gavin Shan [maz: tidy-up bitmap values] Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220502233853.1233742-4-rananta@google.com --- arch/arm64/include/asm/kvm_host.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/arm64/include/asm/kvm_host.h') diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index fef597af0beb..281dfcfd0a4e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -105,9 +105,11 @@ struct kvm_arch_memory_slot { * struct kvm_smccc_features: Descriptor of the hypercall services exposed to the guests * * @std_bmap: Bitmap of standard secure service calls + * @std_hyp_bmap: Bitmap of standard hypervisor service calls */ struct kvm_smccc_features { unsigned long std_bmap; + unsigned long std_hyp_bmap; }; struct kvm_arch { -- cgit From b22216e1a617ca55b41337cd1e057ebc784a65d4 Mon Sep 17 00:00:00 2001 From: Raghavendra Rao Ananta Date: Mon, 2 May 2022 23:38:48 +0000 Subject: KVM: arm64: Add vendor hypervisor firmware register Introduce the firmware register to hold the vendor specific hypervisor service calls (owner value 6) as a bitmap. The bitmap represents the features that'll be enabled for the guest, as configured by the user-space. Currently, this includes support for KVM-vendor features along with reading the UID, represented by bit-0, and Precision Time Protocol (PTP), represented by bit-1. Signed-off-by: Raghavendra Rao Ananta Reviewed-by: Gavin Shan [maz: tidy-up bitmap values] Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220502233853.1233742-5-rananta@google.com --- arch/arm64/include/asm/kvm_host.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/arm64/include/asm/kvm_host.h') diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 281dfcfd0a4e..35a60d766fba 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -106,10 +106,12 @@ struct kvm_arch_memory_slot { * * @std_bmap: Bitmap of standard secure service calls * @std_hyp_bmap: Bitmap of standard hypervisor service calls + * @vendor_hyp_bmap: Bitmap of vendor specific hypervisor service calls */ struct kvm_smccc_features { unsigned long std_bmap; unsigned long std_hyp_bmap; + unsigned long vendor_hyp_bmap; }; struct kvm_arch { -- cgit