On Mon, Apr 03, 2023, Paolo Bonzini wrote:
> Checking that instructions are absent is broken when running with CPU
> models other than the bare metal processor's, because neither VMX nor SVM have
> intercept controls for the instructions.
>
> This can even happen with "-cpu max" when running under nested
> virtualization, which is the current situation in the Fedora KVM job
> on Cirrus-CI:
>
> FAIL: clflushopt (ABSENT)
> FAIL: clwb (ABSENT)
>
> In other words it looks like the features have been marked as disabled
> in the L0 host, while the hardware supports them.
>
> Reported-by: Thomas Huth <thuth@xxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> x86/memory.c | 83 +++++++++++++++++++++++++++++++---------------------
> 1 file changed, 49 insertions(+), 34 deletions(-)
>
> diff --git a/x86/memory.c b/x86/memory.c
> index 351e7c0..58ef835 100644
> --- a/x86/memory.c
> +++ b/x86/memory.c
> @@ -25,53 +25,68 @@ static void handle_ud(struct ex_regs *regs)
>
> int main(int ac, char **av)
> {
> - int expected;
> -
> handle_exception(UD_VECTOR, handle_ud);
>
> /* 3-byte instructions: */
> isize = 3;
We can clean this up even further by utilizing TRY_ASM(). Though I think this is
a good excuse to add things like asm_safe(), asm_safe_report(), and asm_safe_report_ex(),
to cut down on the boilerplate even more. I'll send patches on top.
