Re: merge bouyer-xenpvh to HEAD

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sun, Apr 26, 2020 at 01:25:45PM +0200, Maxime Villard wrote:
> Two late remarks.
> 
> In locore.S:
> 
> 	+	movl	$VM_GUEST_XENPV, _C_LABEL(vm_guest)
> 
> vm_guest being an enum, I don't know if the "movl" is correct. The compiler
> could make vm_guest an uint8_t. I think it should be switched to a fixed-
> size type.

Actually it is 32 bits, I did check it.
Would it make sense for the compiler to change it to 8bits at some point ?

We could CTASSERT that it is 32 bits.

> 
> In vector.S:
> 
> 	+	jmp _C_LABEL(Xhypervisor_pvhvm_callback)
> 	+	TEXT_USER_BEGIN
> 	 IDTVEC(hypervisor_pvhvm_callback)
> 	 	pushq	$0		/* Dummy error code */
> 	 	pushq	$T_ASTFLT
> 	 	INTRENTRY
> 	-	/* sti?? */
> 	+	movl    CPUVAR(ILEVEL),%edi
> 	+	pushq   %rdi /* for Xdoreti */
> 	+	incl	CPUVAR(IDEPTH)
> 	...
> 
> All the code after INTRENTRY should be in a separate function in the .text
> section, because with Meltdown, the code between TEXT_USER_BEGIN and
> TEXT_USER_END is leaked to userland. Here your change leaks more information
> than necessary.
> 
> You can use intr_lapic_ltimer as an example, we leave right after the
> INTRENTRY.

thanks, I'll look at this tomorow

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--