On 05/12/2010 09:33 AM, Sheng Yang wrote:
Only modifying some bits of CR0/CR4 needs paging mode switch.
Add update_rsvd_bits_mask() to address EFER.NX bit updating for reserved bits.
@@ -2335,6 +2335,19 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, int level)
}
}
+void update_rsvd_bits_mask(struct kvm_vcpu *vcpu)
+{
+ if (!is_paging(vcpu))
+ return;
+ if (is_long_mode(vcpu))
+ reset_rsvds_bits_mask(vcpu, PT64_ROOT_LEVEL);
+ else if (is_pae(vcpu))
+ reset_rsvds_bits_mask(vcpu, PT32E_ROOT_LEVEL);
+ else
+ reset_rsvds_bits_mask(vcpu, PT32_ROOT_LEVEL);
+}
+EXPORT_SYMBOL_GPL(update_rsvd_bits_mask);
Needs a kvm_ prefix if made a global symbol. But isn't nx switching
rare enough so we can reload the mmu completely?
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b59fc67..971a295 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -416,6 +416,10 @@ out:
static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
{
+ unsigned long old_cr0 = kvm_read_cr0(vcpu);
+ unsigned long update_bits = X86_CR0_PG | X86_CR0_PE |
+ X86_CR0_CD | X86_CR0_NW;
PE doesn't affect paging, CD, NW don't either?
What about WP?
+
cr0 |= X86_CR0_ET;
#ifdef CONFIG_X86_64
@@ -449,7 +453,8 @@ static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
kvm_x86_ops->set_cr0(vcpu, cr0);
- kvm_mmu_reset_context(vcpu);
+ if ((cr0 ^ old_cr0)& update_bits)
+ kvm_mmu_reset_context(vcpu);
return 0;
}
@@ -692,6 +698,8 @@ static u32 emulated_msrs[] = {
static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
{
+ u64 old_efer = vcpu->arch.efer;
+
if (efer& efer_reserved_bits)
return 1;
@@ -722,6 +730,9 @@ static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
vcpu->arch.mmu.base_role.nxe = (efer& EFER_NX)&& !tdp_enabled;
+ if ((efer ^ old_efer)& EFER_NX)
+ update_rsvd_bits_mask(vcpu);
+
return 0;
}
I think it's fine to reset the entire mmu context here, most guests
won't toggle nx all the time. But it needs to be in patch 3, otherwise
we have a regression between 3 and 4.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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