Re: [Xen-devel] [PATCH v2 7/8] x86/vvmx: correctly report vvmcs size
> From: Sergey Dyasli [mailto:sergey.dya...@citrix.com] > Sent: Tuesday, November 6, 2018 8:08 PM > > 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 Acked-by: Kevin Tian ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] [PATCH v2 7/8] x86/vvmx: correctly report vvmcs size
On Thu, Nov 08, 2018 at 10:28:24AM +, Sergey Dyasli wrote:
> On 07/11/2018 13:28, Wei Liu wrote:
> > On Tue, Nov 06, 2018 at 12:07:58PM +, 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
> >> ---
> >> 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 & 0x7fff);
> >> 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;"
>
Fair enough. I have no objection anymore.
Wei.
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Re: [Xen-devel] [PATCH v2 7/8] x86/vvmx: correctly report vvmcs size
On 07/11/2018 13:28, Wei Liu wrote:
> On Tue, Nov 06, 2018 at 12:07:58PM +, 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
>> ---
>> 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 & 0x7fff);
>> 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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Re: [Xen-devel] [PATCH v2 7/8] x86/vvmx: correctly report vvmcs size
On Tue, Nov 06, 2018 at 12:07:58PM +, 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
> ---
> 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 & 0x7fff);
> 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?
Wei.
> +}
> +
> break;
> }
> case MSR_IA32_VMX_PINBASED_CTLS:
> --
> 2.17.1
>
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