Xen project Mailing List

[PATCH 08/16] xen/sysctl: Drop XEN_SYSCTL_get_cpu_levelling_caps

To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>

From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Date: Mon, 26 Jan 2026 17:53:37 +0000

Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Julian Vetter <julian.vetter@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, "Daniel P . Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>

Delivery-date: Mon, 26 Jan 2026 17:54:06 +0000

List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

This hypercall is an addition of mine from commit 67528a3f0649 ("x86/cpu: Sysctl and common infrastructure for levelling context switching", 2016), but it never got wired into any toolstacks. In the meantime, how we handle CPUID for guests has evolved substantially. In order to reuse the AMD levelling infrasturcture for boot time quirks, levelling_caps is going to have to change. While it's probably safe to expose this difference, it's safer still to make it an internal detail. When re-plummbing the LCAP_* constants, turn them all into single bits. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- CC: Jan Beulich <JBeulich@xxxxxxxx> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx> CC: Julian Vetter <julian.vetter@xxxxxxxxxx> CC: Teddy Astie <teddy.astie@xxxxxxxxxx> CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx> CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx> --- CHANGELOG.md | 2 ++ tools/flask/policy/modules/dom0.te | 1 - tools/include/xenguest.h | 1 - tools/libs/guest/xg_cpuid_x86.c | 14 -------------- xen/arch/x86/include/asm/cpuid.h | 15 ++++++--------- xen/arch/x86/sysctl.c | 6 ------ xen/include/public/sysctl.h | 22 +--------------------- xen/xsm/flask/hooks.c | 4 ---- xen/xsm/flask/policy/access_vectors | 2 -- 9 files changed, 9 insertions(+), 58 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index 18f3d10f20d2..425118bc9ae9 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -19,6 +19,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) - The cpuid_mask_* command line options for legacy CPUs. These were deprecated in Xen 4.7 and noted not to work correctly with AMD CPUs from 2011 onwards, nor work at all with Intel CPUs from 2012. + - The SYSCTL_get_cpu_levelling_caps sysctl. This is not known to have been + used by any toolstack. - Xenoprofile support. Oprofile themselves removed support for Xen in 2014 prior to the version 1.0 release, and there has been no development since before then in Xen. diff --git a/tools/flask/policy/modules/dom0.te b/tools/flask/policy/modules/dom0.te index d30edf8be1fb..aae69041a966 100644 --- a/tools/flask/policy/modules/dom0.te +++ b/tools/flask/policy/modules/dom0.te @@ -43,7 +43,6 @@ allow dom0_t xen_t:xen2 { psr_alloc pmu_ctrl get_symbol - get_cpu_levelling_caps get_cpu_featureset livepatch_op coverage_op diff --git a/tools/include/xenguest.h b/tools/include/xenguest.h index 7c3b8b098352..2a277cb7cd61 100644 --- a/tools/include/xenguest.h +++ b/tools/include/xenguest.h @@ -822,7 +822,6 @@ int xc_cpu_policy_update_msrs(xc_interface *xch, xc_cpu_policy_t *policy, bool xc_cpu_policy_is_compatible(xc_interface *xch, xc_cpu_policy_t *host, xc_cpu_policy_t *guest); -int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps); int xc_get_cpu_featureset(xc_interface *xch, uint32_t index, uint32_t *nr_features, uint32_t *featureset); diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c index 263a9d4787b6..0db6d77cd801 100644 --- a/tools/libs/guest/xg_cpuid_x86.c +++ b/tools/libs/guest/xg_cpuid_x86.c @@ -36,20 +36,6 @@ enum { #define bitmaskof(idx) (1u << ((idx) & 31)) #define featureword_of(idx) ((idx) >> 5) -int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps) -{ - struct xen_sysctl sysctl = {}; - int ret; - - sysctl.cmd = XEN_SYSCTL_get_cpu_levelling_caps; - ret = do_sysctl(xch, &sysctl); - - if ( !ret ) - *caps = sysctl.u.cpu_levelling_caps.caps; - - return ret; -} - int xc_get_cpu_featureset(xc_interface *xch, uint32_t index, uint32_t *nr_features, uint32_t *featureset) { diff --git a/xen/arch/x86/include/asm/cpuid.h b/xen/arch/x86/include/asm/cpuid.h index f1b9e37a42ca..c7ee1d54bc7e 100644 --- a/xen/arch/x86/include/asm/cpuid.h +++ b/xen/arch/x86/include/asm/cpuid.h @@ -15,15 +15,12 @@ extern const uint32_t known_features[FSCAPINTS]; * Expected levelling capabilities (given cpuid vendor/family information), * and levelling capabilities actually available (given MSR probing). */ -#define LCAP_faulting XEN_SYSCTL_CPU_LEVELCAP_faulting -#define LCAP_1cd (XEN_SYSCTL_CPU_LEVELCAP_ecx | \ - XEN_SYSCTL_CPU_LEVELCAP_edx) -#define LCAP_e1cd (XEN_SYSCTL_CPU_LEVELCAP_extd_ecx | \ - XEN_SYSCTL_CPU_LEVELCAP_extd_edx) -#define LCAP_Da1 XEN_SYSCTL_CPU_LEVELCAP_xsave_eax -#define LCAP_6c XEN_SYSCTL_CPU_LEVELCAP_thermal_ecx -#define LCAP_7ab0 (XEN_SYSCTL_CPU_LEVELCAP_l7s0_eax | \ - XEN_SYSCTL_CPU_LEVELCAP_l7s0_ebx) +#define LCAP_faulting (1U << 0) /* CPUID Faulting */ +#define LCAP_1cd (1U << 1) /* 0x00000001.ecx/edx */ +#define LCAP_e1cd (1U << 2) /* 0x80000001.ecx/edx */ +#define LCAP_Da1 (1U << 3) /* 0x0000000D:1.eax */ +#define LCAP_6c (1U << 4) /* 0x00000006.ecx */ +#define LCAP_7ab0 (1U << 5) /* 0x00000007:0.eax/ebx */ extern unsigned int expected_levelling_cap, levelling_caps; struct cpuidmasks diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c index 1b04947516bb..0fbbdd8b280d 100644 --- a/xen/arch/x86/sysctl.c +++ b/xen/arch/x86/sysctl.c @@ -289,12 +289,6 @@ long arch_do_sysctl( break; } - case XEN_SYSCTL_get_cpu_levelling_caps: - sysctl->u.cpu_levelling_caps.caps = levelling_caps; - if ( __copy_field_to_guest(u_sysctl, sysctl, u.cpu_levelling_caps.caps) ) - ret = -EFAULT; - break; - case XEN_SYSCTL_get_cpu_featureset: { static const struct cpu_policy *const policy_table[6] = { diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h index 66c9b65465cc..6b4ec5f7f765 100644 --- a/xen/include/public/sysctl.h +++ b/xen/include/public/sysctl.h @@ -932,25 +932,6 @@ struct xen_sysctl_psr_alloc { } u; }; -/* - * XEN_SYSCTL_get_cpu_levelling_caps (x86 specific) - * - * Return hardware capabilities concerning masking or faulting of the cpuid - * instruction for PV guests. - */ -struct xen_sysctl_cpu_levelling_caps { -#define XEN_SYSCTL_CPU_LEVELCAP_faulting (1UL << 0) /* CPUID faulting */ -#define XEN_SYSCTL_CPU_LEVELCAP_ecx (1UL << 1) /* 0x00000001.ecx */ -#define XEN_SYSCTL_CPU_LEVELCAP_edx (1UL << 2) /* 0x00000001.edx */ -#define XEN_SYSCTL_CPU_LEVELCAP_extd_ecx (1UL << 3) /* 0x80000001.ecx */ -#define XEN_SYSCTL_CPU_LEVELCAP_extd_edx (1UL << 4) /* 0x80000001.edx */ -#define XEN_SYSCTL_CPU_LEVELCAP_xsave_eax (1UL << 5) /* 0x0000000D:1.eax */ -#define XEN_SYSCTL_CPU_LEVELCAP_thermal_ecx (1UL << 6) /* 0x00000006.ecx */ -#define XEN_SYSCTL_CPU_LEVELCAP_l7s0_eax (1UL << 7) /* 0x00000007:0.eax */ -#define XEN_SYSCTL_CPU_LEVELCAP_l7s0_ebx (1UL << 8) /* 0x00000007:0.ebx */ - uint32_t caps; -}; - /* * XEN_SYSCTL_get_cpu_featureset (x86 specific) * @@ -1270,7 +1251,7 @@ struct xen_sysctl { #define XEN_SYSCTL_pcitopoinfo 22 #define XEN_SYSCTL_psr_alloc 23 /* #define XEN_SYSCTL_tmem_op 24 */ -#define XEN_SYSCTL_get_cpu_levelling_caps 25 +/* #define XEN_SYSCTL_get_cpu_levelling_caps 25 */ #define XEN_SYSCTL_get_cpu_featureset 26 #define XEN_SYSCTL_livepatch_op 27 /* #define XEN_SYSCTL_set_parameter 28 */ @@ -1300,7 +1281,6 @@ struct xen_sysctl { struct xen_sysctl_coverage_op coverage_op; struct xen_sysctl_psr_cmt_op psr_cmt_op; struct xen_sysctl_psr_alloc psr_alloc; - struct xen_sysctl_cpu_levelling_caps cpu_levelling_caps; struct xen_sysctl_cpu_featureset cpu_featureset; struct xen_sysctl_livepatch_op livepatch; #if defined(__i386__) || defined(__x86_64__) diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c index b250b2706535..28522dcbd271 100644 --- a/xen/xsm/flask/hooks.c +++ b/xen/xsm/flask/hooks.c @@ -884,10 +884,6 @@ static int cf_check flask_sysctl(int cmd) return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2, XEN2__PSR_ALLOC, NULL); - case XEN_SYSCTL_get_cpu_levelling_caps: - return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2, - XEN2__GET_CPU_LEVELLING_CAPS, NULL); - case XEN_SYSCTL_get_cpu_featureset: return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2, XEN2__GET_CPU_FEATURESET, NULL); diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors index ce907d50a45e..bbb9c117ec4a 100644 --- a/xen/xsm/flask/policy/access_vectors +++ b/xen/xsm/flask/policy/access_vectors @@ -87,8 +87,6 @@ class xen2 pmu_ctrl # PMU use (domains, including unprivileged ones, will be using this operation) pmu_use -# XEN_SYSCTL_get_cpu_levelling_caps - get_cpu_levelling_caps # XEN_SYSCTL_get_cpu_featureset get_cpu_featureset # XEN_SYSCTL_livepatch_op -- 2.39.5

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