Re: [PATCH v3 63/66] KVM: arm64: nv: Allocate VNCR page when required
From: Haibo Xu <hidden>
Date: 2021-01-21 02:49:32
Also in:
kvmarm, linux-arm-kernel
On Fri, 11 Dec 2020 at 00:04, Marc Zyngier [off-list ref] wrote:
quoted hunk ↗ jump to hunk
If running a NV guest on an ARMv8.4-NV capable system, let's allocate an additional page that will be used by the hypervisor to fulfill system register accesses. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/include/asm/kvm_host.h | 3 ++- arch/arm64/kvm/nested.c | 8 ++++++++ arch/arm64/kvm/reset.c | 1 + 3 files changed, 11 insertions(+), 1 deletion(-)diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 78630bd5124d..dada0678c28e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h@@ -523,7 +523,8 @@ struct kvm_vcpu_arch { */ static inline u64 *__ctxt_sys_reg(const struct kvm_cpu_context *ctxt, int r) { - if (unlikely(r >= __VNCR_START__ && ctxt->vncr_array)) + if (unlikely(cpus_have_final_cap(ARM64_HAS_ENHANCED_NESTED_VIRT) && + r >= __VNCR_START__ && ctxt->vncr_array)) return &ctxt->vncr_array[r - __VNCR_START__]; return (u64 *)&ctxt->sys_regs[r];diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index eef8f9873814..88147ec99755 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c@@ -47,6 +47,12 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu) if (!cpus_have_final_cap(ARM64_HAS_NESTED_VIRT)) return -EINVAL; + if (cpus_have_final_cap(ARM64_HAS_ENHANCED_NESTED_VIRT)) { + vcpu->arch.ctxt.vncr_array = (u64 *)__get_free_page(GFP_KERNEL | __GFP_ZERO); + if (!vcpu->arch.ctxt.vncr_array) + return -ENOMEM; + } +
If KVM_ARM_VCPU_INIT was called multiple times, the above codes would try to allocate a new page without free-ing the previous one. Besides that, the following kvm_free_stage2_pgd() call would fail in the second call with the error message "kvm_arch already initialized?". I think a possible fix is to add a new flag to indicate whether the NV related meta data have been initialized, and only initialize them for the first call.
quoted hunk ↗ jump to hunk
mutex_lock(&kvm->lock); /*@@ -64,6 +70,8 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu) kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 2])) { kvm_free_stage2_pgd(&tmp[num_mmus - 1]); kvm_free_stage2_pgd(&tmp[num_mmus - 2]); + free_page((unsigned long)vcpu->arch.ctxt.vncr_array); + vcpu->arch.ctxt.vncr_array = NULL; } else { kvm->arch.nested_mmus_size = num_mmus; ret = 0;diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index 2d2c780e6c69..d281eb39036f 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c@@ -150,6 +150,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu) void kvm_arm_vcpu_destroy(struct kvm_vcpu *vcpu) { kfree(vcpu->arch.sve_state); + free_page((unsigned long)vcpu->arch.ctxt.vncr_array); } static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu) --2.29.2 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm