From f3383cf80e417e86fcc84a2eb4c96bc52842d8d9 Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Mon, 12 May 2014 01:08:32 +0200 Subject: [PATCH] KVM: PPC: Disable NX for old magic page using guests Old guests try to use the magic page, but map their trampoline code inside of an NX region. Since we can't fix those old kernels, try to detect whether the guest is sane or not. If not, just disable NX functionality in KVM so that old guests at least work at all. For newer guests, add a bit that we can set to keep NX functionality available. Signed-off-by: Alexander Graf --- Documentation/virtual/kvm/ppc-pv.txt | 14 ++++++++++++++ arch/powerpc/include/asm/kvm_host.h | 1 + arch/powerpc/include/uapi/asm/kvm_para.h | 6 ++++++ arch/powerpc/kvm/book3s_64_mmu.c | 3 +++ arch/powerpc/kvm/powerpc.c | 14 ++++++++++++-- 5 files changed, 36 insertions(+), 2 deletions(-) diff --git a/Documentation/virtual/kvm/ppc-pv.txt b/Documentation/virtual/kvm/ppc-pv.txt index 4643cde517c4..319560646f32 100644 --- a/Documentation/virtual/kvm/ppc-pv.txt +++ b/Documentation/virtual/kvm/ppc-pv.txt @@ -94,10 +94,24 @@ a bitmap of available features inside the magic page. The following enhancements to the magic page are currently available: KVM_MAGIC_FEAT_SR Maps SR registers r/w in the magic page + KVM_MAGIC_FEAT_MAS0_TO_SPRG7 Maps MASn, ESR, PIR and high SPRGs For enhanced features in the magic page, please check for the existence of the feature before using them! +Magic page flags +================ + +In addition to features that indicate whether a host is capable of a particular +feature we also have a channel for a guest to tell the guest whether it's capable +of something. This is what we call "flags". + +Flags are passed to the host in the low 12 bits of the Effective Address. + +The following flags are currently available for a guest to expose: + + MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correclty wrt magic page + MSR bits ======== diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 29fbb554af5c..bb66d8b8efdf 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -631,6 +631,7 @@ struct kvm_vcpu_arch { #endif unsigned long magic_page_pa; /* phys addr to map the magic page to */ unsigned long magic_page_ea; /* effect. addr to map the magic page to */ + bool disable_kernel_nx; int irq_type; /* one of KVM_IRQ_* */ int irq_cpu_id; diff --git a/arch/powerpc/include/uapi/asm/kvm_para.h b/arch/powerpc/include/uapi/asm/kvm_para.h index e3af3286a068..91e42f09b323 100644 --- a/arch/powerpc/include/uapi/asm/kvm_para.h +++ b/arch/powerpc/include/uapi/asm/kvm_para.h @@ -82,10 +82,16 @@ struct kvm_vcpu_arch_shared { #define KVM_FEATURE_MAGIC_PAGE 1 +/* Magic page flags from host to guest */ + #define KVM_MAGIC_FEAT_SR (1 << 0) /* MASn, ESR, PIR, and high SPRGs */ #define KVM_MAGIC_FEAT_MAS0_TO_SPRG7 (1 << 1) +/* Magic page flags from guest to host */ + +#define MAGIC_PAGE_FLAG_NOT_MAPPED_NX (1 << 0) + #endif /* _UAPI__POWERPC_KVM_PARA_H__ */ diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c index 278729f4df80..774a253ca4e1 100644 --- a/arch/powerpc/kvm/book3s_64_mmu.c +++ b/arch/powerpc/kvm/book3s_64_mmu.c @@ -313,6 +313,9 @@ do_second: gpte->raddr = (r & HPTE_R_RPN & ~eaddr_mask) | (eaddr & eaddr_mask); gpte->page_size = pgsize; gpte->may_execute = ((r & HPTE_R_N) ? false : true); + if (unlikely(vcpu->arch.disable_kernel_nx) && + !(kvmppc_get_msr(vcpu) & MSR_PR)) + gpte->may_execute = true; gpte->may_read = false; gpte->may_write = false; diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index b4e15bf3ff88..154f352c39ae 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -177,8 +177,18 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu) vcpu->arch.shared_big_endian = shared_big_endian; #endif - vcpu->arch.magic_page_pa = param1; - vcpu->arch.magic_page_ea = param2; + if (!(param2 & MAGIC_PAGE_FLAG_NOT_MAPPED_NX)) { + /* + * Older versions of the Linux magic page code had + * a bug where they would map their trampoline code + * NX. If that's the case, remove !PR NX capability. + */ + vcpu->arch.disable_kernel_nx = true; + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); + } + + vcpu->arch.magic_page_pa = param1 & ~0xfffULL; + vcpu->arch.magic_page_ea = param2 & ~0xfffULL; r2 = KVM_MAGIC_FEAT_SR | KVM_MAGIC_FEAT_MAS0_TO_SPRG7; -- 2.39.5