KVM: x86: Warn on zero-size save state for valid CPUID 0xD.N sub-leaf (91001d40) · Commits · 戴 / test

WARN if the save state size for a valid XCR0-managed sub-leaf is zero, which would indicate a KVM or CPU bug. Add a comment to explain why KVM WARNs so the reader doesn't have to tease out the relevant bits from Intel's SDM and KVM's XCR0/XSS code. Reviewed-by:

Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -677,10 +677,17 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
		goto out;

		do_host_cpuid(&entry[i], function, idx);
		if (entry[i].eax == 0)
		continue;
		if (WARN_ON_ONCE(entry[i].ecx & 1))

		/*
		* The @supported check above should have filtered out
		* invalid sub-leafs as well as sub-leafs managed by
		* IA32_XSS MSR. Only XCR0-managed sub-leafs should
		* reach this point, and they should have a non-zero
		* save state size.
		*/
		if (WARN_ON_ONCE(!entry[i].eax \|\| (entry[i].ecx & 1)))
		continue;

		entry[i].ecx = 0;
		entry[i].edx = 0;
		++*nent;

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