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From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
	"Ian Jackson" <Ian.Jackson@citrix.com>,
	"Paul Durrant" <paul@xen.org>, "Wei Liu" <wl@xen.org>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 7/9] x86/hvm: Disable MPX by default
Date: Tue, 16 Jun 2020 11:33:43 +0200	[thread overview]
Message-ID: <58d7254d-8953-93c4-9eb2-9be45f39bc4e@suse.com> (raw)
In-Reply-To: <20200615141532.1927-8-andrew.cooper3@citrix.com>

On 15.06.2020 16:15, Andrew Cooper wrote:
> @@ -479,6 +497,18 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
>          goto out;
>      }
>  
> +    /*
> +     * Account for feature which have been disabled by default since Xen 4.13,
> +     * so migrated-in VM's don't risk seeing features disappearing.
> +     */
> +    if ( restore )
> +    {
> +        if ( di.hvm )
> +        {
> +            p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset);

Why do you derive this from the host featureset instead of the max
one for the guest type? Also, while you modify p here, ...

> +        }
> +    }
> +
>      if ( featureset )
>      {
>          uint32_t disabled_features[FEATURESET_NR_ENTRIES],

... the code in this if()'s body ignores p altogether. I realize the
only caller of the function passes NULL for "featureset", but I'd
like to understand the rationale here anyway before giving an R-b.

Jan


  reply	other threads:[~2020-06-16  9:34 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-15 14:15 [PATCH for-4.14 0/9] XSA-320 follow for IvyBridge Andrew Cooper
2020-06-15 14:15 ` [PATCH 1/9] tools/libx[cl]: Introduce struct xc_xend_cpuid for xc_cpuid_set() Andrew Cooper
2020-06-15 14:51   ` Ian Jackson
2020-06-15 14:15 ` [PATCH 2/9] tests/cpu-policy: Confirm that CPUID serialisation is sorted Andrew Cooper
2020-06-15 14:52   ` Ian Jackson
2020-06-15 15:00     ` Andrew Cooper
2020-06-15 15:34       ` Ian Jackson
2020-06-15 16:12         ` Andrew Cooper
2020-06-16  6:51           ` Jan Beulich
2020-06-16  9:01   ` Jan Beulich
2020-06-15 14:15 ` [PATCH 3/9] tools/libx[cl]: Move processing loop down into xc_cpuid_set() Andrew Cooper
2020-06-15 14:54   ` Ian Jackson
2020-06-16  9:16   ` Jan Beulich
2020-06-16 15:58     ` Andrew Cooper
2020-06-15 14:15 ` [PATCH 4/9] tools/libx[cl]: Merge xc_cpuid_set() into xc_cpuid_apply_policy() Andrew Cooper
2020-06-15 14:55   ` Ian Jackson
2020-06-15 14:15 ` [PATCH 5/9] tools/libx[cl]: Plumb bool restore down " Andrew Cooper
2020-06-15 14:55   ` Ian Jackson
2020-06-15 14:15 ` [PATCH 6/9] x86/gen-cpuid: Distinguish default vs max in feature annotations Andrew Cooper
2020-06-15 14:15 ` [PATCH 7/9] x86/hvm: Disable MPX by default Andrew Cooper
2020-06-16  9:33   ` Jan Beulich [this message]
2020-06-16 16:15     ` Andrew Cooper
2020-06-17 10:32       ` Jan Beulich
2020-06-17 11:16         ` Andrew Cooper
2020-06-17 11:24           ` Jan Beulich
2020-06-17 11:28             ` Andrew Cooper
2020-06-17 11:41               ` Jan Beulich
2020-06-17 11:47                 ` Andrew Cooper
2020-06-15 14:15 ` [PATCH 8/9] x86/cpuid: Introduce missing feature adjustment in calculate_pv_def_policy() Andrew Cooper
2020-06-16  9:40   ` Jan Beulich
2020-06-16 16:17     ` Andrew Cooper
2020-06-15 14:15 ` [PATCH 9/9] x86/spec-ctrl: Hide RDRAND by default on IvyBridge Andrew Cooper
2020-06-16 10:00   ` Jan Beulich
2020-06-16 16:26     ` Andrew Cooper
2020-06-17 10:39       ` Jan Beulich
2020-06-17 11:21         ` Andrew Cooper
2020-06-15 17:04 ` [PATCH for-4.14 0/9] XSA-320 follow for IvyBridge Paul Durrant
2020-06-17 12:46   ` Paul Durrant
2020-06-18  7:18 ` Jan Beulich
2020-06-18  9:37   ` Andrew Cooper

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