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Re: [PATCH] x86/xen: silence smatch warning in pmu_msr_chk_emulated()
- To: Juergen Gross <jgross@xxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Thu, 20 Oct 2022 10:22:17 -0400
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- Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Dan Carpenter <dan.carpenter@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx
- Delivery-date: Thu, 20 Oct 2022 14:23:07 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 10/20/22 9:34 AM, Juergen Gross wrote:
On 20.10.22 15:16, Jan Beulich wrote:
On 20.10.2022 13:37, Juergen Gross wrote:
Commit 8714f7bcd3c2 ("xen/pv: add fault recovery control to pmu msr
accesses") introduced code resulting in a warning issued by the smatch
static checker, claiming to use an uninitialized variable.
This is a false positive, but work around the warning nevertheless.
The risk of introducing a problem might be quite low here, but in general
it exists: With the adjustment you remove any chance of the compiler
spotting a missing initialization before use. And I'm not convinced using
0 in such a case would actually be ending up sufficiently benign.
Hmm, an alternative would be to initialize it to -1 and add a test for the
index to be >= 0 before using it.
Or to live with the smash warning with the chance, that a compiler might be
warning for the same reason in the future.
Is smatch complaining about both variables or just index? There are two cases
in is_intel_pmu_msr() where it returns true but index is not set so perhaps
that's what bothers smatch? It shold not complain if is_intel_pmu_msr() returns
false.
-boris
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