[v2,8/9] KVM: SVM: Use default rAX size for INVLPGA emulation
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Message ID 20210422022128.3464144-9-seanjc@google.com
State New
Headers show
  • KVM: x86: Fixes for (benign?) truncation bugs
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Commit Message

Sean Christopherson April 22, 2021, 2:21 a.m. UTC
Drop bits 63:32 of RAX when grabbing the address for INVLPGA emulation
outside of 64-bit mode to make KVM's emulation slightly less wrong.  The
address for INVLPGA is determined by the effective address size, i.e.
it's not hardcoded to 64/32 bits for a given mode.  Add a FIXME to call
out that the emulation is wrong.

Opportunistically tweak the ASID handling to make it clear that it's
defined by ECX, not rCX.

Per the APM:
   The portion of rAX used to form the address is determined by the
   effective address size (current execution mode and optional address
   size prefix). The ASID is taken from ECX.

Fixes: ff092385e828 ("KVM: SVM: Implement INVLPGA")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
 arch/x86/kvm/svm/svm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

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diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 6df12d7967db..ccf9499f2683 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2301,11 +2301,17 @@  static int clgi_interception(struct kvm_vcpu *vcpu)
 static int invlpga_interception(struct kvm_vcpu *vcpu)
-	trace_kvm_invlpga(to_svm(vcpu)->vmcb->save.rip, kvm_rcx_read(vcpu),
-			  kvm_rax_read(vcpu));
+	gva_t gva = kvm_rax_read(vcpu);
+	u32 asid = kvm_rcx_read(vcpu);
+	/* FIXME: Handle an address size prefix. */
+	if (!is_long_mode(vcpu))
+		gva = (u32)gva;
+	trace_kvm_invlpga(to_svm(vcpu)->vmcb->save.rip, asid, gva);
 	/* Let's treat INVLPGA the same as INVLPG (can be optimized!) */
-	kvm_mmu_invlpg(vcpu, kvm_rax_read(vcpu));
+	kvm_mmu_invlpg(vcpu, gva);
 	return kvm_skip_emulated_instruction(vcpu);