From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Igor Druzhinin <igor.druzhinin@citrix.com>,
wl@xen.org, Jan Beulich <jbeulich@suse.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH] x86/svm: retry after unhandled NPT fault if gfn was marked for recalculation
Date: Fri, 22 May 2020 15:32:59 +0200 [thread overview]
Message-ID: <20200522133259.GC54375@Air-de-Roger> (raw)
In-Reply-To: <ef3411ac-9e7c-0ef7-ad9f-c24f8ebf32a6@citrix.com>
On Fri, May 22, 2020 at 02:11:15PM +0100, Andrew Cooper wrote:
> On 22/05/2020 14:04, Jan Beulich wrote:
> > On 22.05.2020 13:11, Roger Pau Monné wrote:
> >> That being said, I also don't like the fact that logdity is handled
> >> differently between EPT and NPT, as on EPT it's handled as a
> >> misconfig while on NPT it's handled as a violation.
> > Because, well, there is no concept of misconfig in NPT.
>
> Indeed. Intel chose to split EPT errors into two - MISCONFIG for
> structural errors (not present, or reserved bits set) and VIOLATION for
> permissions errors.
>
> AMD reused the same silicon pagewalker design, so have a single
> NPT_FAULT vmexit which behaves much more like a regular pagefault,
> encoding structural vs permission errors in the error code.
Maybe I should clarify, I understand that NPT doesn't have such
differentiation regarding nested page table faults vs EPT, but I feel
like it would be clearer if part of the code could be shared, ie:
unify EPT resolve_misconfig and NPT do_recalc into a single function
for example that uses the necessary p2m-> helpers for the differing
implementations. I think we should be able to tell apart when a NPT
page fault is a recalc one by looking at the bits in the EXITINFO1
error field?
Anyway, this was just a rant, and it's tangential to the issue at
hand, sorry for distracting.
Roger.
next prev parent reply other threads:[~2020-05-22 13:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 21:43 [PATCH] x86/svm: retry after unhandled NPT fault if gfn was marked for recalculation Igor Druzhinin
2020-05-22 0:26 ` Igor Druzhinin
2020-05-22 9:45 ` Andrew Cooper
2020-05-22 10:05 ` Igor Druzhinin
2020-05-22 10:19 ` Andrew Cooper
2020-05-22 10:25 ` Igor Druzhinin
2020-05-22 13:34 ` Jan Beulich
2020-05-22 10:08 ` Roger Pau Monné
2020-05-22 10:14 ` Igor Druzhinin
2020-05-22 10:23 ` Roger Pau Monné
2020-05-22 10:27 ` Igor Druzhinin
2020-05-22 11:11 ` Roger Pau Monné
2020-05-22 13:04 ` Jan Beulich
2020-05-22 13:11 ` Andrew Cooper
2020-05-22 13:32 ` Roger Pau Monné [this message]
2020-05-22 15:53 ` Andrew Cooper
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