On 12/08/2010 07:12 PM, Nadav Har'El wrote:
KVM's "Lazy FPU loading" means that sometimes L0 needs to set CR0.TS, even
if a guest didn't set it. Moreover, L0 must also trap CR0.TS changes and
NM exceptions, even if we have a guest hypervisor (L1) who didn't want these
traps. And of course, conversely: If L1 wanted to trap these events, we
must let it, even if L0 is not interested in them.
This patch fixes some existing KVM code (in update_exception_bitmap(),
vmx_fpu_activate(), vmx_fpu_deactivate()) to do the correct merging of L0's
and L1's needs. Note that handle_cr() was already fixed in the above patch,
and that new code in introduced in previous patches already handles CR0
correctly (see prepare_vmcs02(), prepare_vmcs12(), and nested_vmx_vmexit()).
@@ -1415,8 +1424,19 @@ static void vmx_fpu_activate(struct kvm_
cr0&= ~(X86_CR0_TS | X86_CR0_MP);
cr0 |= kvm_read_cr0_bits(vcpu, X86_CR0_TS | X86_CR0_MP);
vmcs_writel(GUEST_CR0, cr0);
- update_exception_bitmap(vcpu);
vcpu->arch.cr0_guest_owned_bits = X86_CR0_TS;
+ if (is_guest_mode(vcpu)) {
+ /* While we (L0) no longer care about NM exceptions or cr0.TS
+ * changes, our guest hypervisor (L1) might care in which case
+ * we must trap them for it.
+ */
+ u32 eb = vmcs_read32(EXCEPTION_BITMAP)& ~(1u<< NM_VECTOR);
+ struct vmcs_fields *vmcs12 = get_vmcs12_fields(vcpu);
+ eb |= vmcs12->exception_bitmap;
+ vcpu->arch.cr0_guest_owned_bits&= ~vmcs12->cr0_guest_host_mask;
+ vmcs_write32(EXCEPTION_BITMAP, eb);
+ } else
+ update_exception_bitmap(vcpu);
Isn't update_exception_bitmap() sufficient for both cases?
vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
}
@@ -1424,12 +1444,24 @@ static void vmx_decache_cr0_guest_bits(s
static void vmx_fpu_deactivate(struct kvm_vcpu *vcpu)
{
+ /* Note that there is no vcpu->fpu_active = 0 here. The caller must
+ * set this *before* calling this function.
+ */
vmx_decache_cr0_guest_bits(vcpu);
vmcs_set_bits(GUEST_CR0, X86_CR0_TS | X86_CR0_MP);
- update_exception_bitmap(vcpu);
+ vmcs_write32(EXCEPTION_BITMAP,
+ vmcs_read32(EXCEPTION_BITMAP) | (1u<< NM_VECTOR));
Why not fold the logic into update_exception_bitmap()?
vcpu->arch.cr0_guest_owned_bits = 0;
vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
- vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0);
+ if (is_guest_mode(vcpu))
+ /* Unfortunately in nested mode we play with arch.cr0's PG
+ * bit, so we musn't copy it all, just the relevant TS bit
+ */
+ vmcs_writel(CR0_READ_SHADOW,
+ (vmcs_readl(CR0_READ_SHADOW)& ~X86_CR0_TS) |
+ (vcpu->arch.cr0& X86_CR0_TS));
+ else
+ vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0);
Didn't you have a nice guest_readable_cr0() function that did this?
}
static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
--
error compiling committee.c: too many arguments to function
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