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From: Jan Beulich <jbeulich@suse.com>
To: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Ian Jackson" <iwj@xenproject.org>,
	"Julien Grall" <julien@xen.org>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: [PATCH v3 03/22] x86/xstate: re-size save area when CPUID policy changes
Date: Thu, 22 Apr 2021 16:44:59 +0200	[thread overview]
Message-ID: <8ba8f016-0aed-277b-bbea-80022d057791@suse.com> (raw)
In-Reply-To: <322de6db-e01f-0b57-5777-5d94a13c441a@suse.com>

vCPU-s get maximum size areas allocated initially. Hidden (and in
particular default-off) features may allow for a smaller size area to
suffice.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: Use 1ul instead of 1ull. Re-base.
---
This could be further shrunk if we used XSAVEC / if we really used
XSAVES, as then we don't need to also cover the holes. But since we
currently use neither of the two in reality, this would require more
work than just adding the alternative size calculation here.

Seeing that both vcpu_init_fpu() and cpuid_policy_updated() get called
from arch_vcpu_create(), I'm not sure we really need this two-stage
approach - the slightly longer period of time during which
v->arch.xsave_area would remain NULL doesn't look all that problematic.
But since xstate_alloc_save_area() gets called for idle vCPU-s, it has
to stay anyway in some form, so the extra code churn may not be worth
it.

Instead of cpuid_policy_xcr0_max(), cpuid_policy_xstates() may be the
interface to use here. But it remains to be determined whether the
xcr0_accum field is meant to be inclusive of XSS (in which case it would
better be renamed) or exclusive. Right now there's no difference as we
don't support any XSS-controlled features.

--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -281,7 +281,21 @@ void update_guest_memory_policy(struct v
     }
 }
 
-void domain_cpu_policy_changed(struct domain *d)
+/*
+ * Called during vcpu construction, and each time the toolstack changes the
+ * CPUID configuration for the domain.
+ */
+static int __must_check cpuid_policy_updated(struct vcpu *v)
+{
+    int rc = xstate_update_save_area(v);
+
+    if ( !rc && is_hvm_vcpu(v) )
+        hvm_cpuid_policy_changed(v);
+
+    return rc;
+}
+
+int domain_cpu_policy_changed(struct domain *d)
 {
     const struct cpuid_policy *p = d->arch.cpuid;
     struct vcpu *v;
@@ -439,13 +453,18 @@ void domain_cpu_policy_changed(struct do
 
     for_each_vcpu ( d, v )
     {
-        cpuid_policy_updated(v);
+        int rc = cpuid_policy_updated(v);
+
+        if ( rc )
+            return rc;
 
         /* If PMU version is zero then the guest doesn't have VPMU */
         if ( boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
              p->basic.pmu_version == 0 )
             vpmu_destroy(v);
     }
+
+    return 0;
 }
 
 #ifndef CONFIG_BIGMEM
@@ -584,7 +603,7 @@ int arch_vcpu_create(struct vcpu *v)
     {
         vpmu_initialise(v);
 
-        cpuid_policy_updated(v);
+        rc = cpuid_policy_updated(v);
     }
 
     return rc;
@@ -859,11 +878,11 @@ int arch_domain_create(struct domain *d,
      */
     d->arch.x87_fip_width = cpu_has_fpu_sel ? 0 : 8;
 
-    domain_cpu_policy_changed(d);
-
     d->arch.msr_relaxed = config->arch.misc_flags & XEN_X86_MSR_RELAXED;
 
-    return 0;
+    rc = domain_cpu_policy_changed(d);
+    if ( !rc )
+        return 0;
 
  fail:
     d->is_dying = DOMDYING_dead;
@@ -2471,16 +2490,6 @@ int domain_relinquish_resources(struct d
     return 0;
 }
 
-/*
- * Called during vcpu construction, and each time the toolstack changes the
- * CPUID configuration for the domain.
- */
-void cpuid_policy_updated(struct vcpu *v)
-{
-    if ( is_hvm_vcpu(v) )
-        hvm_cpuid_policy_changed(v);
-}
-
 void arch_dump_domain_info(struct domain *d)
 {
     paging_dump_domain_info(d);
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -89,7 +89,7 @@ static int update_domain_cpu_policy(stru
     recalculate_cpuid_policy(d);
 
     /* Recalculate relevant dom/vcpu state now the policy has changed. */
-    domain_cpu_policy_changed(d);
+    ret = domain_cpu_policy_changed(d);
 
  out:
     /* Free whichever cpuid/msr structs are not installed in struct domain. */
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -542,6 +542,41 @@ int xstate_alloc_save_area(struct vcpu *
     return 0;
 }
 
+int xstate_update_save_area(struct vcpu *v)
+{
+    unsigned int i, size, old;
+    struct xsave_struct *save_area;
+    uint64_t xcr0_max = cpuid_policy_xcr0_max(v->domain->arch.cpuid);
+
+    ASSERT(!is_idle_vcpu(v));
+
+    if ( !cpu_has_xsave )
+        return 0;
+
+    if ( v->arch.xcr0_accum & ~xcr0_max )
+        return -EBUSY;
+
+    for ( size = old = XSTATE_AREA_MIN_SIZE, i = 2; i < xstate_features; ++i )
+    {
+        if ( xcr0_max & (1ul << i) )
+            size = max(size, xstate_offsets[i] + xstate_sizes[i]);
+        if ( v->arch.xcr0_accum & (1ul << i) )
+            old = max(old, xstate_offsets[i] + xstate_sizes[i]);
+    }
+
+    save_area = _xvrealloc(v->arch.xsave_area, size, __alignof(*save_area));
+    if ( !save_area )
+        return -ENOMEM;
+
+    ASSERT(old <= size);
+    memset((void *)save_area + old, 0, size - old);
+
+    v->arch.xsave_area = save_area;
+    v->arch.fpu_ctxt = &v->arch.xsave_area->fpu_sse;
+
+    return 0;
+}
+
 void xstate_free_save_area(struct vcpu *v)
 {
     XVFREE(v->arch.xsave_area);
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -78,8 +78,6 @@ void toggle_guest_mode(struct vcpu *);
 /* x86/64: toggle guest page tables between kernel and user modes. */
 void toggle_guest_pt(struct vcpu *);
 
-void cpuid_policy_updated(struct vcpu *v);
-
 /*
  * Initialise a hypercall-transfer page. The given pointer must be mapped
  * in Xen virtual address space (accesses are not validated or checked).
@@ -670,7 +668,7 @@ struct guest_memory_policy
 void update_guest_memory_policy(struct vcpu *v,
                                 struct guest_memory_policy *policy);
 
-void domain_cpu_policy_changed(struct domain *d);
+int __must_check domain_cpu_policy_changed(struct domain *d);
 
 bool update_runstate_area(struct vcpu *);
 bool update_secondary_system_time(struct vcpu *,
--- a/xen/include/asm-x86/xstate.h
+++ b/xen/include/asm-x86/xstate.h
@@ -106,6 +106,7 @@ void compress_xsave_states(struct vcpu *
 /* extended state init and cleanup functions */
 void xstate_free_save_area(struct vcpu *v);
 int xstate_alloc_save_area(struct vcpu *v);
+int xstate_update_save_area(struct vcpu *v);
 void xstate_init(struct cpuinfo_x86 *c);
 unsigned int xstate_ctxt_size(u64 xcr0);
 



  parent reply	other threads:[~2021-04-22 14:45 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-22 14:38 [PATCH v3 00/22] xvmalloc() / x86 xstate area / x86 CPUID / AMX+XFD Jan Beulich
2021-04-22 14:43 ` [PATCH v3 01/22] mm: introduce xvmalloc() et al and use for grant table allocations Jan Beulich
2021-05-03 11:31   ` Roger Pau Monné
2021-05-03 13:50     ` Jan Beulich
2021-05-03 14:54       ` Roger Pau Monné
2021-05-03 15:21         ` Jan Beulich
2021-05-03 16:39           ` Roger Pau Monné
2021-04-22 14:44 ` [PATCH v3 02/22] x86/xstate: use xvzalloc() for save area allocation Jan Beulich
2021-05-05 13:29   ` Roger Pau Monné
2021-04-22 14:44 ` Jan Beulich [this message]
2021-05-03 13:57   ` [PATCH v3 03/22] x86/xstate: re-size save area when CPUID policy changes Andrew Cooper
2021-05-03 14:22     ` Jan Beulich
2021-05-11 16:41       ` Andrew Cooper
2021-05-17  7:33         ` Jan Beulich
2021-04-22 14:45 ` [PATCH v3 04/22] x86/xstate: re-use valid_xcr0() for boot-time checks Jan Beulich
2021-05-03 11:53   ` Andrew Cooper
2021-04-22 14:45 ` [PATCH v3 05/22] x86/xstate: drop xstate_offsets[] and xstate_sizes[] Jan Beulich
2021-05-03 16:10   ` Andrew Cooper
2021-05-04  7:57     ` Jan Beulich
2021-04-22 14:46 ` [PATCH v3 06/22] x86/xstate: replace xsave_cntxt_size and drop XCNTXT_MASK Jan Beulich
2021-04-22 14:47 ` [PATCH v3 07/22] x86/xstate: avoid accounting for unsupported components Jan Beulich
2021-04-22 14:47 ` [PATCH v3 08/22] x86: use xvmalloc() for extended context buffer allocations Jan Beulich
2021-04-22 14:48 ` [PATCH v3 09/22] x86/xstate: enable AMX components Jan Beulich
2021-04-22 14:50 ` [PATCH v3 10/22] x86/CPUID: adjust extended leaves out of range clearing Jan Beulich
2021-04-22 14:50 ` [PATCH v3 11/22] x86/CPUID: move bounding of max_{,sub}leaf fields to library code Jan Beulich
2021-04-22 14:51 ` [PATCH v3 12/22] x86/CPUID: enable AMX leaves Jan Beulich
2021-04-22 14:52 ` [PATCH v3 13/22] x86: XFD enabling Jan Beulich
2021-04-22 14:53 ` [PATCH v3 14/22] x86emul: introduce X86EMUL_FPU_{tilecfg,tile} Jan Beulich
2021-04-22 14:53 ` [PATCH v3 15/22] x86emul: support TILERELEASE Jan Beulich
2021-04-22 14:53 ` [PATCH v3 16/22] x86: introduce struct for TILECFG register Jan Beulich
2021-04-22 14:54 ` [PATCH v3 17/22] x86emul: support {LD,ST}TILECFG Jan Beulich
2021-04-22 14:55 ` [PATCH v3 18/22] x86emul: support TILEZERO Jan Beulich
2021-04-22 14:55 ` [PATCH v3 19/22] x86emul: support TILELOADD{,T1} and TILESTORE Jan Beulich
2021-04-22 15:06   ` Jan Beulich
2021-04-22 15:11     ` Jan Beulich
2021-04-26  7:12       ` Paul Durrant
2021-04-29  9:40         ` Jan Beulich
2021-04-22 14:56 ` [PATCH v3 20/22] x86emul: support tile multiplication insns Jan Beulich
2021-04-22 14:57 ` [PATCH v3 21/22] x86emul: test AMX insns Jan Beulich
2021-04-22 14:57 ` [PATCH v3 22/22] x86: permit guests to use AMX and XFD Jan Beulich

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