Re: [PATCH 1/2] KVM: x86/emulator: Defer not-present segment check in __load_segment_descriptor()

[Sean Christopherson]

On Thu, Jan 20, 2022, Hou Wenlong wrote:
> Per Intel's SDM on the "Instruction Set Reference", when
> loading segment descriptor, not-present segment check should
> be after all type and privilege checks. But the emulator checks
> it first, then #NP is triggered instead of #GP if privilege fails
> and segment is not present. Put not-present segment check after
> type and privilege checks in __load_segment_descriptor().

For posterity, KVM doesn't support CALL GATES or TASK GATES, so the "early" #NP
check for those is missing.

> Fixes: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c)
> Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
> ---

Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>