From: Jan Beulich <jbeulich@suse.com>
To: Roger Pau Monne <roger.pau@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Anthony PERARD <anthony.perard@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 15/21] libs/guest: obtain a compatible cpu policy from two input ones
Date: Wed, 14 Apr 2021 15:49:02 +0200 [thread overview]
Message-ID: <391b56d0-bb4d-8d3c-231c-e2e3ad7e2f42@suse.com> (raw)
In-Reply-To: <20210413140140.73690-16-roger.pau@citrix.com>
On 13.04.2021 16:01, Roger Pau Monne wrote:
> @@ -944,3 +945,130 @@ bool xc_cpu_policy_is_compatible(xc_interface *xch, const xc_cpu_policy_t host,
>
> return false;
> }
> +
> +static uint64_t level_msr(unsigned int index, uint64_t val1, uint64_t val2)
> +{
> + uint64_t val = val1 & val2;;
For arbitrary MSRs this isn't going to do any good. If only very
specific MSRs are assumed to make it here, I think this wants
commenting on.
Also, nit: stray semicolon.
> + switch ( index )
> + {
> + case MSR_ARCH_CAPABILITIES:
> + /*
> + * Set RSBA if present on any of the input values to notice the guest
> + * might run on vulnerable hardware at some point.
> + */
> + val |= (val1 | val2) & ARCH_CAPS_RSBA;
> + break;
> + }
> +
> + return val;
> +}
> +
> +static bool level_leaf(xen_cpuid_leaf_t *l1, xen_cpuid_leaf_t *l2,
const (twice)?
> + xen_cpuid_leaf_t *out)
> +{
> + *out = (xen_cpuid_leaf_t){ };
> +
> + switch ( l1->leaf )
> + {
> + case 0x1:
> + case 0x80000001:
> + out->c = l1->c & l2->c;
> + out->d = l1->d & l2->d;
> + return true;
> +
> + case 0xd:
> + if ( l1->subleaf != 1 )
> + break;
> + out->a = l1->a & l2->a;
> + return true;
Could you explain your thinking behind this (a code comment would
likely help)? You effectively discard everything except subleaf 1
by returning false in that case, don't you?
> + case 0x7:
> + switch ( l1->subleaf )
> + {
> + case 0:
> + out->b = l1->b & l2->b;
> + out->c = l1->c & l2->c;
> + out->d = l1->d & l2->d;
> + return true;
> +
> + case 1:
> + out->a = l1->a & l2->a;
> + return true;
> + }
> + break;
Can we perhaps assume all subleaves here are going to hold flags,
and hence and both sides together without regard to what subleaf
we're actually dealing with (subleaf 1 remaining special as to
EAX of course)? This would avoid having to remember to make yet
another mechanical change when enabling a new subleaf.
> + case 0x80000007:
> + out->d = l1->d & l2->d;
> + return true;
> +
> + case 0x80000008:
> + out->b = l1->b & l2->b;
> + return true;
> + }
> +
> + return false;
> +}
Considering your LFENCE-always-serializing patch, I assume
whichever ends up going in last will take care of adding handling
of that leaf here?
Jan
next prev parent reply other threads:[~2021-04-14 13:49 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 14:01 [PATCH v2 00/21] libs/guest: new CPUID/MSR interface Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 01/21] libxl: don't ignore the return value from xc_cpuid_apply_policy Roger Pau Monne
2021-04-28 15:13 ` Anthony PERARD
2021-04-13 14:01 ` [PATCH v2 02/21] libs/guest: rename xc_get_cpu_policy_size to xc_cpu_policy_get_size Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 03/21] libs/guest: introduce xc_cpu_policy_t Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 04/21] libs/guest: introduce helper to fetch a system cpu policy Roger Pau Monne
2021-04-14 13:28 ` Jan Beulich
2021-04-13 14:01 ` [PATCH v2 05/21] libs/guest: introduce helper to fetch a domain " Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 06/21] libs/guest: introduce helper to serialize a " Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 07/21] tools: switch existing users of xc_get_{system,domain}_cpu_policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 08/21] libs/guest: introduce a helper to apply a cpu policy to a domain Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 09/21] libs/guest: allow fetching a specific CPUID leaf from a cpu policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 10/21] tests/cpu-policy: add sorted MSR test Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 11/21] libs/guest: allow fetching a specific MSR entry from a cpu policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 12/21] libs/guest: allow updating a cpu policy CPUID data Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 13/21] libs/guest: allow updating a cpu policy MSR data Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 14/21] libs/guest: introduce helper to check cpu policy compatibility Roger Pau Monne
2021-04-14 13:36 ` Jan Beulich
2021-04-22 8:22 ` Roger Pau Monné
2021-04-22 8:31 ` Jan Beulich
2021-04-13 14:01 ` [PATCH v2 15/21] libs/guest: obtain a compatible cpu policy from two input ones Roger Pau Monne
2021-04-14 13:49 ` Jan Beulich [this message]
2021-04-22 9:42 ` Roger Pau Monné
2021-04-22 9:58 ` Jan Beulich
2021-04-22 10:34 ` Roger Pau Monné
2021-04-22 10:48 ` Jan Beulich
2021-04-22 10:56 ` Roger Pau Monné
2021-04-22 11:05 ` Jan Beulich
2021-04-22 11:37 ` Roger Pau Monné
2021-04-22 11:42 ` Jan Beulich
2021-04-22 12:07 ` Roger Pau Monné
2021-04-22 12:08 ` Jan Beulich
2021-04-21 10:22 ` Wei Liu
2021-04-21 11:26 ` Roger Pau Monné
2021-04-21 16:42 ` Wei Liu
2021-04-13 14:01 ` [PATCH v2 16/21] libs/guest: make a cpu policy compatible with older Xen versions Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 17/21] libs/guest: introduce helper set cpu topology in cpu policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 18/21] libs/guest: rework xc_cpuid_xend_policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 19/21] libs/guest: apply a featureset into a cpu policy Roger Pau Monne
2021-04-13 14:01 ` [PATCH v2 20/21] libs/{light,guest}: implement xc_cpuid_apply_policy in libxl Roger Pau Monne
2021-04-28 16:19 ` Anthony PERARD
2021-04-13 14:01 ` [PATCH v2 21/21] libs/guest: (re)move xc_cpu_policy_apply_cpuid Roger Pau Monne
2021-04-28 16:45 ` Anthony PERARD
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