On 07/11/2018 13:28, Wei Liu wrote:
> On Tue, Nov 06, 2018 at 12:07:58PM +0000, Sergey Dyasli wrote:
>> The size of Xen's virtual vmcs region is 4096 bytes (see comment about
>> Virtual VMCS layout in include/asm-x86/hvm/vmx/vvmx.h). Correctly report
>> it to the guest in case when VMCS shadowing is not available instead of
>> providing H/W value (which is usually smaller).
>>
>> Signed-off-by: Sergey Dyasli <sergey.dya...@citrix.com>
>> ---
>> v2:
>> - slight commit message change
>> ---
>> xen/arch/x86/hvm/vmx/vvmx.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
>> index 2f5370ceed..37d3cdd859 100644
>> --- a/xen/arch/x86/hvm/vmx/vvmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
>> @@ -2101,6 +2101,14 @@ int nvmx_msr_read_intercept(unsigned int msr, u64
>> *msr_content)
>> data = (host_data & (~0ul << 32)) |
>> (vmcs->vmcs_revision_id & 0x7fffffff);
>> unmap_domain_page(vmcs);
>> +
>> + if ( !cpu_has_vmx_vmcs_shadowing )
>> + {
>> + /* Report vmcs_region_size as 4096 */
>> + data &= ~VMX_BASIC_VMCS_SIZE_MASK;
>> + data |= 1ULL << 44;
>
> Can you introduce a define for this to avoid using a magic number?
I don't see much point in making a define for several reasons:
1. It's not going to be used anywhere else
2. Intel SDM clearly states that VMCS size is "at most 4096 (bit 44
is set if and only if bits 43:32 are clear)"
3. My VMX MSRs series will introduce a nice struct, after which this
assignment will look like "basic.vmcs_region_size = 4096;"
--
Thanks,
Sergey
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