Re: [Crash-utility] increase __PHYSICAL_MASK_SHIFT_XEN

Date: Mon, 25 Jan 2021 22:44:50 +0100 From: Jiri Bohac <jbohac(a)suse.cz&gt; To: lijiang <lijiang(a)redhat.com&gt; Cc: crash-utility(a)redhat.com Subject: [Crash-utility] [PATCH] increase __PHYSICAL_MASK_SHIFT_XEN Message-ID: <20210125214450.n5qvx6pjg2otslrm(a)dwarf.suse.cz&gt; Content-Type: text/plain; charset=us-ascii The current value of __PHYSICAL_MASK_SHIFT_XEN in crash (40) is smaller than the kernel (52) since kernel commit 6f0e8bf167 (xen: support 52 bit physical addresses in pv guests). This can cause x86_64_pud_offset() to lose the most significant bits of pgd_pte, leading to a failed xen_m2p() translation, resulting in crash failing with an error message like this: crash: read error: physical address: ffffffffffffffff type: "pud page" Both Intel and AMD documentation mandate that unused physical address bits must be 0, so there is no need to explicitly mask them out with a mask narrower than the architecture limit of 52. This is also confirmed by this kernel commit: b83ce5ee91. Increase the value of __PHYSICAL_MASK_SHIFT_XEN to 52. Signed-off-by: Jiri Bohac <jbohac(a)suse.cz&gt; diff --git a/defs.h b/defs.h index e468b1d..848c1f6 100644 --- a/defs.h +++ b/defs.h @@ -3583,7 +3583,7 @@ struct arm64_stackframe { * PHYSICAL_PAGE_MASK changed (enlarged) between 2.4 and 2.6, so * for safety, use the 2.6 values to generate it. */ -#define __PHYSICAL_MASK_SHIFT_XEN 40 +#define __PHYSICAL_MASK_SHIFT_XEN 52 #define __PHYSICAL_MASK_SHIFT_2_6 46 #define __PHYSICAL_MASK_SHIFT_5LEVEL 52 #define __PHYSICAL_MASK_SHIFT (machdep->machspec->physical_mask_shift)

-- Jiri Bohac <jbohac(a)suse.cz&gt; SUSE Labs, Prague, Czechia