Re: [PATCH v2 1/3] x86/xen: use clear_bss() for Xen PV guests

From: Juergen Gross
Date: Tue Jun 28 2022 - 08:03:20 EST

On 23.06.22 11:51, Jan Beulich wrote:
On 23.06.2022 11:46, Juergen Gross wrote:
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1183,15 +1183,19 @@ static void __init xen_domu_set_legacy_features(void)
extern void early_xen_iret_patch(void);
/* First C function to be called on Xen boot */
-asmlinkage __visible void __init xen_start_kernel(void)
+asmlinkage __visible void __init xen_start_kernel(struct start_info *si)
{
struct physdev_set_iopl set_iopl;
unsigned long initrd_start = 0;
int rc;
- if (!xen_start_info)
+ if (!si)
return;
+ clear_bss();

As per subsequent observation, this shouldn't really be needed: The
hypervisor (or tool stack for DomU-s) already does so. While I guess
we want to keep it to be on the safe side, maybe worth a comment?

Are you sure all possible boot loaders are clearing alloc-only sections?

I'd rather not count on e.g. grub doing this in all cases.


Juergen

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