Re: [PATCH 7/8] x86/hvm: Drop restore boolean from hvm_cr4_guest_valid_bits()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 01/10/2020 12:00, Roger Pau Monné wrote:
> On Wed, Sep 30, 2020 at 02:42:47PM +0100, Andrew Cooper wrote:
>> Previously, migration was reordered so the CPUID data was available before
>> register state.  nestedhvm_enabled() has recently been made accurate for the
>> entire lifetime of the domain.
>>
>> Therefore, we can drop the bodge in hvm_cr4_guest_valid_bits() which existed
>> previously to tolerate a guests' CR4 being set/restored before
>> HVM_PARAM_NESTEDHVM.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks,

>
> Thanks, just one nit below.
>
>> ---
>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> CC: Wei Liu <wl@xxxxxxx>
>> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
>> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
>> ---
>>  xen/arch/x86/hvm/domain.c       | 2 +-
>>  xen/arch/x86/hvm/hvm.c          | 8 ++++----
>>  xen/arch/x86/hvm/svm/svmdebug.c | 6 ++++--
>>  xen/arch/x86/hvm/vmx/vmx.c      | 2 +-
>>  xen/arch/x86/hvm/vmx/vvmx.c     | 2 +-
>>  xen/include/asm-x86/hvm/hvm.h   | 2 +-
>>  6 files changed, 12 insertions(+), 10 deletions(-)
>>
>> diff --git a/xen/arch/x86/hvm/domain.c b/xen/arch/x86/hvm/domain.c
>> index 8e3375265c..0ce132b308 100644
>> --- a/xen/arch/x86/hvm/domain.c
>> +++ b/xen/arch/x86/hvm/domain.c
>> @@ -275,7 +275,7 @@ int arch_set_info_hvm_guest(struct vcpu *v, const 
>> vcpu_hvm_context_t *ctx)
>>      if ( v->arch.hvm.guest_efer & EFER_LME )
>>          v->arch.hvm.guest_efer |= EFER_LMA;
>>  
>> -    if ( v->arch.hvm.guest_cr[4] & ~hvm_cr4_guest_valid_bits(d, false) )
>> +    if ( v->arch.hvm.guest_cr[4] & ~hvm_cr4_guest_valid_bits(d) )
>>      {
>>          gprintk(XENLOG_ERR, "Bad CR4 value: %#016lx\n",
>>                  v->arch.hvm.guest_cr[4]);
>> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
>> index 101a739952..54e32e4fe8 100644
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -972,14 +972,14 @@ const char *hvm_efer_valid(const struct vcpu *v, 
>> uint64_t value,
>>          X86_CR0_CD | X86_CR0_PG)))
>>  
>>  /* These bits in CR4 can be set by the guest. */
>> -unsigned long hvm_cr4_guest_valid_bits(const struct domain *d, bool restore)
>> +unsigned long hvm_cr4_guest_valid_bits(const struct domain *d)
>>  {
>>      const struct cpuid_policy *p = d->arch.cpuid;
>>      bool mce, vmxe;
>>  
>>      /* Logic broken out simply to aid readability below. */
>>      mce  = p->basic.mce || p->basic.mca;
>> -    vmxe = p->basic.vmx && (restore || nestedhvm_enabled(d));
>> +    vmxe = p->basic.vmx && nestedhvm_enabled(d);
>>  
>>      return ((p->basic.vme     ? X86_CR4_VME | X86_CR4_PVI : 0) |
>>              (p->basic.tsc     ? X86_CR4_TSD               : 0) |
>> @@ -1033,7 +1033,7 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
>> hvm_domain_context_t *h)
>>          return -EINVAL;
>>      }
>>  
>> -    if ( ctxt.cr4 & ~hvm_cr4_guest_valid_bits(d, true) )
>> +    if ( ctxt.cr4 & ~hvm_cr4_guest_valid_bits(d) )
>>      {
>>          printk(XENLOG_G_ERR "HVM%d restore: bad CR4 %#" PRIx64 "\n",
>>                 d->domain_id, ctxt.cr4);
>> @@ -2425,7 +2425,7 @@ int hvm_set_cr4(unsigned long value, bool may_defer)
>>      struct vcpu *v = current;
>>      unsigned long old_cr;
>>  
>> -    if ( value & ~hvm_cr4_guest_valid_bits(v->domain, false) )
>> +    if ( value & ~hvm_cr4_guest_valid_bits(v->domain) )
>>      {
>>          HVM_DBG_LOG(DBG_LEVEL_1,
>>                      "Guest attempts to set reserved bit in CR4: %lx",
>> diff --git a/xen/arch/x86/hvm/svm/svmdebug.c 
>> b/xen/arch/x86/hvm/svm/svmdebug.c
>> index ba26b6a80b..f450391df4 100644
>> --- a/xen/arch/x86/hvm/svm/svmdebug.c
>> +++ b/xen/arch/x86/hvm/svm/svmdebug.c
>> @@ -106,6 +106,7 @@ bool svm_vmcb_isvalid(const char *from, const struct 
>> vmcb_struct *vmcb,
>>      unsigned long cr0 = vmcb_get_cr0(vmcb);
>>      unsigned long cr3 = vmcb_get_cr3(vmcb);
>>      unsigned long cr4 = vmcb_get_cr4(vmcb);
>> +    unsigned long valid;
> Could you init valid here at definition time? Also cr4_valid might be
> a better name since the sacope of the variable is quite wide.

I have some further cleanup in mind, which is why I did it like this.

~Andrew