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Revert "nSVM: Check for reserved encodings of TLB_CONTROL in nested VMCB" 

[ Upstream commit a484755ab2 ]

Revert KVM's made-up consistency check on SVM's TLB control.  The APM says
that unsupported encodings are reserved, but the APM doesn't state that
VMRUN checks for a supported encoding.  Unless something is called out
in "Canonicalization and Consistency Checks" or listed as MBZ (Must Be
Zero), AMD behavior is typically to let software shoot itself in the foot.

This reverts commit 174a921b69.

Fixes: 174a921b69 ("nSVM: Check for reserved encodings of TLB_CONTROL in nested VMCB")
Reported-by: Stefan Sterz <s.sterz@proxmox.com>
Closes: https://lkml.kernel.org/r/b9915c9c-4cf6-051a-2d91-44cc6380f455%40proxmox.com
Cc: stable@vger.kernel.org
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20231018194104.1896415-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sean Christopherson 2023-10-18 12:41:03 -07:00 committed by Greg Kroah-Hartman
parent c519a9054b
commit fafda9f08a
1 changed files with 0 additions and 14 deletions
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14
arch/x86/kvm/svm/nested.c
View File

@ -239,18 +239,6 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size)
kvm_vcpu_is_legal_gpa(vcpu, addr + size - 1);
}
static bool nested_svm_check_tlb_ctl(struct kvm_vcpu *vcpu, u8 tlb_ctl)
{
/* Nested FLUSHBYASID is not supported yet. */
switch(tlb_ctl) {
case TLB_CONTROL_DO_NOTHING:
case TLB_CONTROL_FLUSH_ALL_ASID:
return true;
default:
return false;
}
}
static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
struct vmcb_ctrl_area_cached *control)
{
@ -270,8 +258,6 @@ static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
IOPM_SIZE)))
return false;
if (CC(!nested_svm_check_tlb_ctl(vcpu, control->tlb_ctl)))
return false;
return true;
}