From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Roger Pau Monne <roger.pau@citrix.com>, <xen-devel@lists.xenproject.org>
Cc: Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH v3 02/13] libs/guest: allow fetching a specific CPUID leaf from a cpu policy
Date: Tue, 4 May 2021 12:59:43 +0100 [thread overview]
Message-ID: <76e5e596-24bc-9d91-e654-cef1115e5139@citrix.com> (raw)
In-Reply-To: <20210430155211.3709-3-roger.pau@citrix.com>
On 30/04/2021 16:52, Roger Pau Monne wrote:
> @@ -822,3 +825,28 @@ int xc_cpu_policy_serialise(xc_interface *xch, const xc_cpu_policy_t p,
> errno = 0;
> return 0;
> }
> +
> +int xc_cpu_policy_get_cpuid(xc_interface *xch, const xc_cpu_policy_t policy,
> + uint32_t leaf, uint32_t subleaf,
> + xen_cpuid_leaf_t *out)
> +{
> + unsigned int nr_leaves = ARRAY_SIZE(policy->leaves);
> + xen_cpuid_leaf_t *tmp;
> + int rc;
> +
> + rc = xc_cpu_policy_serialise(xch, policy, policy->leaves, &nr_leaves,
> + NULL, 0);
> + if ( rc )
> + return rc;
Sorry for not spotting this last time.
You don't need to serialise. You can look up leaf/subleaf in O(1) time
from cpuid_policy, which was a design goal of the structure originally.
It is probably best to adapt most of the first switch statement in
guest_cpuid() to be a libx86 function. The asserts aren't massively
interesting to keep, and instead of messing around with nospec, just
have the function return a pointer into the cpuid_policy (or NULL), and
have a single block_speculation() in Xen. We'll also want a unit test
to go with this new function to check that out-of-range leaves don't
result in out-of-bounds reads.
~Andrew
next prev parent reply other threads:[~2021-05-04 12:00 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 15:51 [PATCH v3 00/13] libs/guest: new CPUID/MSR interface Roger Pau Monne
2021-04-30 15:51 ` [PATCH v3 01/13] libxl: don't ignore the return value from xc_cpuid_apply_policy Roger Pau Monne
2021-05-04 14:07 ` Anthony PERARD
2021-04-30 15:52 ` [PATCH v3 02/13] libs/guest: allow fetching a specific CPUID leaf from a cpu policy Roger Pau Monne
2021-05-04 11:59 ` Andrew Cooper [this message]
2021-05-04 13:47 ` Roger Pau Monné
2021-05-04 15:46 ` Andrew Cooper
2021-04-30 15:52 ` [PATCH v3 03/13] libs/guest: allow fetching a specific MSR entry " Roger Pau Monne
2021-05-03 10:41 ` Jan Beulich
2021-05-04 10:56 ` Roger Pau Monné
2021-05-04 11:40 ` Jan Beulich
2021-05-04 11:58 ` Roger Pau Monné
2021-05-04 17:11 ` Andrew Cooper
2021-05-05 7:38 ` Jan Beulich
2021-04-30 15:52 ` [PATCH v3 04/13] libs/guest: allow updating a cpu policy CPUID data Roger Pau Monne
2021-05-04 16:19 ` Andrew Cooper
2021-04-30 15:52 ` [PATCH v3 05/13] libs/guest: allow updating a cpu policy MSR data Roger Pau Monne
2021-05-04 16:20 ` Andrew Cooper
2021-04-30 15:52 ` [PATCH v3 06/13] libs/guest: introduce helper to check cpu policy compatibility Roger Pau Monne
2021-05-04 16:27 ` Andrew Cooper
2021-04-30 15:52 ` [PATCH v3 07/13] libs/guest: obtain a compatible cpu policy from two input ones Roger Pau Monne
2021-05-03 10:43 ` Jan Beulich
2021-05-04 11:56 ` Roger Pau Monné
2021-05-04 12:12 ` Jan Beulich
2021-05-04 16:50 ` Andrew Cooper
2021-04-30 15:52 ` [PATCH v3 08/13] libs/guest: make a cpu policy compatible with older Xen versions Roger Pau Monne
2021-05-03 11:09 ` Jan Beulich
2021-05-04 15:34 ` Roger Pau Monné
2021-05-05 7:42 ` Jan Beulich
2021-05-06 10:23 ` Roger Pau Monné
2021-05-06 10:52 ` Jan Beulich
2021-04-30 15:52 ` [PATCH v3 09/13] libs/guest: introduce helper set cpu topology in cpu policy Roger Pau Monne
2021-04-30 15:52 ` [PATCH v3 10/13] libs/guest: rework xc_cpuid_xend_policy Roger Pau Monne
2021-04-30 15:52 ` [PATCH v3 11/13] libs/guest: apply a featureset into a cpu policy Roger Pau Monne
2021-04-30 15:52 ` [PATCH v3 12/13] libs/{light,guest}: implement xc_cpuid_apply_policy in libxl Roger Pau Monne
2021-05-04 14:08 ` Anthony PERARD
2021-04-30 15:52 ` [PATCH v3 13/13] libs/guest: (re)move xc_cpu_policy_apply_cpuid Roger Pau Monne
2021-05-04 14:08 ` Anthony PERARD
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