On 12/08/2010 07:03 PM, Nadav Har'El wrote:
This patch includes a utility function for decoding pointer operands of VMX instructions issued by L1 (a guest hypervisor)Signed-off-by: Nadav Har'El<n...@il.ibm.com> --- arch/x86/kvm/vmx.c | 59 +++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/x86.c | 3 +- arch/x86/kvm/x86.h | 3 ++ 3 files changed, 64 insertions(+), 1 deletion(-) --- .before/arch/x86/kvm/x86.c 2010-12-08 18:56:49.000000000 +0200 +++ .after/arch/x86/kvm/x86.c 2010-12-08 18:56:49.000000000 +0200 @@ -3688,7 +3688,7 @@ static int kvm_fetch_guest_virt(gva_t ad exception); } -static int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes, +int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes, struct kvm_vcpu *vcpu, struct x86_exception *exception) { @@ -3696,6 +3696,7 @@ static int kvm_read_guest_virt(gva_t add return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access, exception); } +EXPORT_SYMBOL_GPL(kvm_read_guest_virt); static int kvm_read_guest_virt_system(gva_t addr, void *val, unsigned int bytes, struct kvm_vcpu *vcpu, --- .before/arch/x86/kvm/x86.h 2010-12-08 18:56:49.000000000 +0200 +++ .after/arch/x86/kvm/x86.h 2010-12-08 18:56:49.000000000 +0200 @@ -74,6 +74,9 @@ void kvm_before_handle_nmi(struct kvm_vc void kvm_after_handle_nmi(struct kvm_vcpu *vcpu); int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq); +int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes, + struct kvm_vcpu *vcpu, struct x86_exception *exception); + void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data); #endif --- .before/arch/x86/kvm/vmx.c 2010-12-08 18:56:49.000000000 +0200 +++ .after/arch/x86/kvm/vmx.c 2010-12-08 18:56:49.000000000 +0200 @@ -3936,6 +3936,65 @@ static int handle_vmoff(struct kvm_vcpu } /* + * Decode the memory-address operand of a vmx instruction, as recorded on an + * exit caused by such an instruction (run by a guest hypervisor). + * On success, returns 0. When the operand is invalid, returns 1 and throws + * #UD or #GP. + */ +static int get_vmx_mem_address(struct kvm_vcpu *vcpu, + unsigned long exit_qualification, + u32 vmx_instruction_info, gva_t *ret) +{ + /* + * According to Vol. 3B, "Information for VM Exits Due to Instruction + * Execution", on an exit, vmx_instruction_info holds most of the + * addressing components of the operand. Only the displacement part + * is put in exit_qualification (see 3B, "Basic VM-Exit Information"). + * For how an actual address is calculated from all these components, + * refer to Vol. 1, "Operand Addressing". + */ + int scaling = vmx_instruction_info& 3; + int addr_size = (vmx_instruction_info>> 7)& 7; + bool is_reg = vmx_instruction_info& (1u<< 10); + int seg_reg = (vmx_instruction_info>> 15)& 7; + int index_reg = (vmx_instruction_info>> 18)& 0xf; + bool index_is_valid = !(vmx_instruction_info& (1u<< 22)); + int base_reg = (vmx_instruction_info>> 23)& 0xf; + bool base_is_valid = !(vmx_instruction_info& (1u<< 27)); + + if (is_reg) { + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; + } + + switch (addr_size) { + case 1: /* 32 bit. high bits are undefined according to the spec: */ + exit_qualification&= 0xffffffff;
Best to do this at the end, on *ret, so that segment base + offset is subject to truncation.
+ break; + case 2: /* 64 bit */ + break; + default: /* 16 bit */ + return 1; + } + + /* Addr = segment_base + offset */ + /* offset = base + [index * scale] + displacement */ + *ret = vmx_get_segment_base(vcpu, seg_reg); + if (base_is_valid) + *ret += kvm_register_read(vcpu, base_reg); + if (index_is_valid) + *ret += kvm_register_read(vcpu, index_reg)<<scaling; + *ret += exit_qualification; /* holds the displacement */ + /* + * TODO: throw #GP (and return 1) in various cases that the VM* + * instructions require it - e.g., offset beyond segment limit, + * unusable or unreadable/unwritable segment, non-canonical 64-bit + * address, and so on. Currently these are not checked. + */ + return 0; +} +
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