> -----Original Message----- > From: Gleb Natapov [mailto:gleb@xxxxxxxxxx] > Sent: Wednesday, November 21, 2012 9:27 PM > To: Xu, Dongxiao > Cc: kvm@xxxxxxxxxxxxxxx; mtosatti@xxxxxxxxxx > Subject: Re: [PATCH 1/4] nested vmx: clean up for vmcs12 read and write > > On Wed, Nov 21, 2012 at 05:04:34PM +0800, Dongxiao Xu wrote: > > abstract vmcs12_read and vmcs12_write functions to do the vmcs12 > > read/write operations. > > > > Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx> > > --- > > arch/x86/kvm/vmx.c | 86 > +++++++++++++++++++++++++++------------------------- > > 1 files changed, 45 insertions(+), 41 deletions(-) > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index > > f858159..d8670e4 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -5407,32 +5407,67 @@ static inline int vmcs_field_readonly(unsigned > long field) > > * some of the bits we return here (e.g., on 32-bit guests, only 32 bits of > > * 64-bit fields are to be returned). > > */ > > -static inline bool vmcs12_read_any(struct kvm_vcpu *vcpu, > > - unsigned long field, u64 *ret) > > +static inline u64 vmcs12_read(struct kvm_vcpu *vcpu, unsigned long > > +field) > > { > > short offset = vmcs_field_to_offset(field); > > char *p; > > > > - if (offset < 0) > > + if (offset < 0) { > > + nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > + skip_emulated_instruction(vcpu); > > return 0; > > + } > > > > p = ((char *)(get_vmcs12(vcpu))) + offset; > > > > switch (vmcs_field_type(field)) { > > case VMCS_FIELD_TYPE_NATURAL_WIDTH: > > - *ret = *((natural_width *)p); > > + return *((natural_width *)p); > > + case VMCS_FIELD_TYPE_U16: > > + return *((u16 *)p); > > + case VMCS_FIELD_TYPE_U32: > > + return *((u32 *)p); > > + case VMCS_FIELD_TYPE_U64: > > + return *((u64 *)p); > > + default: > > + nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > + skip_emulated_instruction(vcpu); > > + return 0; /* can never happen. */ > > + } > > +} > > + > > +static inline int vmcs12_write(struct kvm_vcpu *vcpu, > > + unsigned long field, > > + u64 value) > > +{ > > + short offset = vmcs_field_to_offset(field); > > + char *p; > > + > > + if (offset < 0) { > > + nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > + skip_emulated_instruction(vcpu); > > + return 0; > > + } > > + > > + p = ((char *)(get_vmcs12(vcpu))) + offset; > > + > > + switch (vmcs_field_type(field)) { > > + case VMCS_FIELD_TYPE_NATURAL_WIDTH: > > + *(natural_width *)p = value; > > return 1; > > case VMCS_FIELD_TYPE_U16: > > - *ret = *((u16 *)p); > > + *(u16 *)p = value; > > return 1; > > case VMCS_FIELD_TYPE_U32: > > - *ret = *((u32 *)p); > > + *(u32 *)p = value; > > return 1; > > case VMCS_FIELD_TYPE_U64: > > - *ret = *((u64 *)p); > > + *(u64 *)p = value; > > return 1; > > default: > > - return 0; /* can never happen. */ > > + nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > + skip_emulated_instruction(vcpu); > > + return 0; > > } > > } > > > > @@ -5466,11 +5501,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu) > > /* Decode instruction info and find the field to read */ > > field = kvm_register_read(vcpu, (((vmx_instruction_info) >> 28) & 0xf)); > > /* Read the field, zero-extended to a u64 field_value */ > > - if (!vmcs12_read_any(vcpu, field, &field_value)) { > > - nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > - skip_emulated_instruction(vcpu); > > - return 1; > > - } > > + field_value = vmcs12_read(vcpu, field); > You do not handle failure here and always write back field_value even if > vmcs12_read() failed. Actually now it is impossible to detect a failure. Call to > nested_vmx_failValid() in vmcs12_read() will be overwritten by call to > nested_vmx_succeed() at the end of > handle_vmread() and skip_emulated_instruction() will be called twice. Thanks Gleb and Orit to raise this issue. What about moving the offset check outside the vmcs12_read() and vmcs12_write() function, and put it directly in handle_vmread() and handle_vmwrite()? I think we only need to do offset error check in handle_vmread() and handle_vmwrite() since they are to emulate correct behavior for guest VMM. For example, if guest VMM reads a field that is not valid or writes a field that is read only, then in emulation code handle_vmread() and handle_vmwrite, we need to raise error to guest VMM. For other calling of vmcs12_read() and vmcs12_write() functions in KVM hypervisor (see PATCH 3/4), actually the caller needs to ensure the field should be valid. Otherwise it is a bug in KVM hypervisor itself. Does it make sense? If so, I will revise this patch according to above. Thanks, Dongxiao > > > + skip_emulated_instruction(vcpu); > > > /* > > * Now copy part of this value to register or memory, as requested. > > * Note that the number of bits actually copied is 32 or 64 > > depending @@ -5500,8 +5531,6 @@ static int handle_vmwrite(struct > kvm_vcpu *vcpu) > > gva_t gva; > > unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION); > > u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO); > > - char *p; > > - short offset; > > /* The value to write might be 32 or 64 bits, depending on L1's long > > * mode, and eventually we need to write that into a field of several > > * possible lengths. The code below first zero-extends the value to > > 64 @@ -5537,33 +5566,8 @@ static int handle_vmwrite(struct kvm_vcpu > *vcpu) > > skip_emulated_instruction(vcpu); > > return 1; > > } > > - > > - offset = vmcs_field_to_offset(field); > > - if (offset < 0) { > > - nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > - skip_emulated_instruction(vcpu); > > - return 1; > > - } > > - p = ((char *) get_vmcs12(vcpu)) + offset; > > - > > - switch (vmcs_field_type(field)) { > > - case VMCS_FIELD_TYPE_U16: > > - *(u16 *)p = field_value; > > - break; > > - case VMCS_FIELD_TYPE_U32: > > - *(u32 *)p = field_value; > > - break; > > - case VMCS_FIELD_TYPE_U64: > > - *(u64 *)p = field_value; > > - break; > > - case VMCS_FIELD_TYPE_NATURAL_WIDTH: > > - *(natural_width *)p = field_value; > > - break; > > - default: > > - nested_vmx_failValid(vcpu, > VMXERR_UNSUPPORTED_VMCS_COMPONENT); > > - skip_emulated_instruction(vcpu); > > + if (!vmcs12_write(vcpu, field, field_value)) > > return 1; > > - } > > > > nested_vmx_succeed(vcpu); > > skip_emulated_instruction(vcpu); > > -- > > 1.7.1 > > -- > Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
