Re: [PATCH v3 7/7] KVM, pkeys: disable PKU feature without ept

[Paolo Bonzini]

On 18/11/2015 06:44, Huaitong Han wrote:
> This patch disables CPUID:PKU without ept, becase pkeys is not supported
> with softmmu.

Sure, but _what_ makes it impossible to support pkeys with shadow pages?

Is it enough to add the pkey bits to the role (and then to
kvm_get_mmu_page, mmu_set_spte, set_spte) or are there fundamental problems?

The trick to handle !CR0.WP in FNAME(page_fault) (search for
"walker.pte_access &= ~ACC_USER_MASK"; it's documented in
Documentation/virtual/kvm/mmu.txt as well) should work for PKRU.

If you just want me to change it to "is not yet implemented for shadow
paging", I can do that.

Thanks,

Paolo

> Signed-off-by: Huaitong Han 
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Re: [PATCH v3 7/7] KVM, pkeys: disable PKU feature without ept

[Han, Huaitong]

On Wed, 2015-11-18 at 10:06 +0100, Paolo Bonzini wrote:
> 
> On 18/11/2015 06:44, Huaitong Han wrote:
> > This patch disables CPUID:PKU without ept, becase pkeys is not
> > supported
> > with softmmu.
> 
> Sure, but _what_ makes it impossible to support pkeys with shadow
> pages?
> 
> Is it enough to add the pkey bits to the role (and then to
> kvm_get_mmu_page, mmu_set_spte, set_spte) or are there fundamental
> problems?
> 
> The trick to handle !CR0.WP in FNAME(page_fault) (search for
> "walker.pte_access &= ~ACC_USER_MASK"; it's documented in
> Documentation/virtual/kvm/mmu.txt as well) should work for PKRU.
> 
> If you just want me to change it to "is not yet implemented for
> shadow
> paging", I can do that.

Yes, the comments should be described as "becase pkeys is not yet
implemented for shadow paging."

Thanks
Huaitong.

> 
> Thanks,
> 
> Paolo
> 
> > Signed-off-by: Huaitong Han 
> > N�r��yb�X��ǧv�^�)޺{.n�+h����ܨ}���Ơz�:+v���zZ+��+zf���h���~i���z��w���?�&�)ߢf

[PATCH v3 7/7] KVM, pkeys: disable PKU feature without ept

[Huaitong Han]

This patch disables CPUID:PKU without ept, becase pkeys is not supported
with softmmu.

Signed-off-by: Huaitong Han 

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index ece687b..e422f0a 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -447,6 +447,9 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 
*entry, u32 function,
entry->ebx |= F(TSC_ADJUST);
entry->ecx &= kvm_supported_word11_x86_features;
cpuid_mask(>ecx, 13);
+   if (!tdp_enabled)
+   /* PKU cannot work with softmmu */
+   entry->ecx &= ~F(PKU);
} else {
entry->ebx = 0;
entry->ecx = 0;
-- 
2.4.3

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