[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[xen staging] x86/fpu: Combine fpu_ctxt and xsave_area in arch_vcpu



commit edb48e76458bb93b89daa4bfb621f4419262d370
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Mon Oct 7 16:52:39 2024 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Oct 21 18:28:59 2024 +0100

    x86/fpu: Combine fpu_ctxt and xsave_area in arch_vcpu
    
    fpu_ctxt is either a pointer to the legacy x87/SSE save area (used by 
FXSAVE) or
    a pointer aliased with xsave_area that points to its fpu_sse subfield. Such
    subfield is at the base and is identical in size and layout to the legacy
    buffer.
    
    This patch merges the 2 pointers in the arch_vcpu into a single XSAVE area. 
In
    the very rare case in which the host doesn't support XSAVE all we're doing 
is
    wasting a tiny amount of memory and trading those for a lot more simplicity 
in
    the code.
    
    While at it, dedup the setup logic in vcpu_init_fpu() and integrate it
    into xstate_alloc_save_area().
    
    Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/domctl.c             |  6 +++++-
 xen/arch/x86/hvm/emulate.c        |  4 ++--
 xen/arch/x86/hvm/hvm.c            |  6 +++++-
 xen/arch/x86/i387.c               | 44 ++++++---------------------------------
 xen/arch/x86/include/asm/domain.h |  6 ------
 xen/arch/x86/x86_emulate/blk.c    |  2 +-
 xen/arch/x86/xstate.c             | 12 ++++++++---
 7 files changed, 28 insertions(+), 52 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 37ebcb3abb..5f01111619 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1383,7 +1383,11 @@ void arch_get_info_guest(struct vcpu *v, 
vcpu_guest_context_u c)
 #define c(fld) (c.nat->fld)
 #endif
 
-    memcpy(&c.nat->fpu_ctxt, v->arch.fpu_ctxt, sizeof(c.nat->fpu_ctxt));
+    BUILD_BUG_ON(sizeof(c.nat->fpu_ctxt) !=
+                 sizeof(v->arch.xsave_area->fpu_sse));
+    memcpy(&c.nat->fpu_ctxt, &v->arch.xsave_area->fpu_sse,
+           sizeof(c.nat->fpu_ctxt));
+
     if ( is_pv_domain(d) )
         c(flags = v->arch.pv.vgc_flags & ~(VGCF_i387_valid|VGCF_in_kernel));
     else
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index aa97ca1cbf..f2bc6967df 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2371,7 +2371,7 @@ static int cf_check hvmemul_get_fpu(
         alternative_vcall(hvm_funcs.fpu_dirty_intercept);
     else if ( type == X86EMUL_FPU_fpu )
     {
-        const fpusse_t *fpu_ctxt = curr->arch.fpu_ctxt;
+        const fpusse_t *fpu_ctxt = &curr->arch.xsave_area->fpu_sse;
 
         /*
          * Latch current register state so that we can back out changes
@@ -2411,7 +2411,7 @@ static void cf_check hvmemul_put_fpu(
 
     if ( aux )
     {
-        fpusse_t *fpu_ctxt = curr->arch.fpu_ctxt;
+        fpusse_t *fpu_ctxt = &curr->arch.xsave_area->fpu_sse;
         bool dval = aux->dval;
         int mode = hvm_guest_x86_mode(curr);
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 3b803e15e0..000b40d7b1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -914,7 +914,11 @@ static int cf_check hvm_save_cpu_ctxt(struct vcpu *v, 
hvm_domain_context_t *h)
 
     if ( v->fpu_initialised )
     {
-        memcpy(ctxt.fpu_regs, v->arch.fpu_ctxt, sizeof(ctxt.fpu_regs));
+        BUILD_BUG_ON(sizeof(ctxt.fpu_regs) !=
+                     sizeof(v->arch.xsave_area->fpu_sse));
+        memcpy(ctxt.fpu_regs, &v->arch.xsave_area->fpu_sse,
+               sizeof(ctxt.fpu_regs));
+
         ctxt.flags = XEN_X86_FPU_INITIALISED;
     }
 
diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c
index 134e0bece5..b0a50f9489 100644
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -39,7 +39,7 @@ static inline void fpu_xrstor(struct vcpu *v, uint64_t mask)
 /* Restore x87 FPU, MMX, SSE and SSE2 state */
 static inline void fpu_fxrstor(struct vcpu *v)
 {
-    const fpusse_t *fpu_ctxt = v->arch.fpu_ctxt;
+    const fpusse_t *fpu_ctxt = &v->arch.xsave_area->fpu_sse;
 
     /*
      * Some CPUs don't save/restore FDP/FIP/FOP unless an exception
@@ -151,7 +151,7 @@ static inline void fpu_xsave(struct vcpu *v)
 /* Save x87 FPU, MMX, SSE and SSE2 state */
 static inline void fpu_fxsave(struct vcpu *v)
 {
-    fpusse_t *fpu_ctxt = v->arch.fpu_ctxt;
+    fpusse_t *fpu_ctxt = &v->arch.xsave_area->fpu_sse;
     unsigned int fip_width = v->domain->arch.x87_fip_width;
 
     if ( fip_width != 4 )
@@ -212,7 +212,7 @@ void vcpu_restore_fpu_nonlazy(struct vcpu *v, bool 
need_stts)
      * above) we also need to restore full state, to prevent subsequently
      * saving state belonging to another vCPU.
      */
-    if ( v->arch.fully_eager_fpu || (v->arch.xsave_area && xstate_all(v)) )
+    if ( v->arch.fully_eager_fpu || xstate_all(v) )
     {
         if ( cpu_has_xsave )
             fpu_xrstor(v, XSTATE_ALL);
@@ -299,44 +299,15 @@ void save_fpu_enable(void)
 /* Initialize FPU's context save area */
 int vcpu_init_fpu(struct vcpu *v)
 {
-    int rc;
-
     v->arch.fully_eager_fpu = opt_eager_fpu;
 
-    if ( (rc = xstate_alloc_save_area(v)) != 0 )
-        return rc;
-
-    if ( v->arch.xsave_area )
-        v->arch.fpu_ctxt = &v->arch.xsave_area->fpu_sse;
-    else
-    {
-        BUILD_BUG_ON(__alignof(v->arch.xsave_area->fpu_sse) < 16);
-        v->arch.fpu_ctxt = _xzalloc(sizeof(v->arch.xsave_area->fpu_sse),
-                                    __alignof(v->arch.xsave_area->fpu_sse));
-        if ( v->arch.fpu_ctxt )
-        {
-            fpusse_t *fpu_sse = v->arch.fpu_ctxt;
-
-            fpu_sse->fcw = FCW_DEFAULT;
-            fpu_sse->mxcsr = MXCSR_DEFAULT;
-        }
-        else
-            rc = -ENOMEM;
-    }
-
-    return rc;
+    return xstate_alloc_save_area(v);
 }
 
 void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area,
                     const void *data, unsigned int fcw_default)
 {
-    /*
-     * For the entire function please note that vcpu_init_fpu() (above) points
-     * v->arch.fpu_ctxt into v->arch.xsave_area when XSAVE is available. Hence
-     * accesses through both pointers alias one another, and the shorter form
-     * is used here.
-     */
-    fpusse_t *fpu_sse = v->arch.fpu_ctxt;
+    fpusse_t *fpu_sse = &v->arch.xsave_area->fpu_sse;
 
     ASSERT(!xsave_area || xsave_area == v->arch.xsave_area);
 
@@ -373,10 +344,7 @@ void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct 
*xsave_area,
 /* Free FPU's context save area */
 void vcpu_destroy_fpu(struct vcpu *v)
 {
-    if ( v->arch.xsave_area )
-        xstate_free_save_area(v);
-    else
-        xfree(v->arch.fpu_ctxt);
+    xstate_free_save_area(v);
 }
 
 /*
diff --git a/xen/arch/x86/include/asm/domain.h 
b/xen/arch/x86/include/asm/domain.h
index 5219c4fb0f..b79d6badd7 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -591,12 +591,6 @@ struct pv_vcpu
 
 struct arch_vcpu
 {
-    /*
-     * guest context (mirroring struct vcpu_guest_context) common
-     * between pv and hvm guests
-     */
-
-    void              *fpu_ctxt;
     struct cpu_user_regs user_regs;
 
     /* Debug registers. */
diff --git a/xen/arch/x86/x86_emulate/blk.c b/xen/arch/x86/x86_emulate/blk.c
index e790f4f900..08a05f8453 100644
--- a/xen/arch/x86/x86_emulate/blk.c
+++ b/xen/arch/x86/x86_emulate/blk.c
@@ -11,7 +11,7 @@
     !defined(X86EMUL_NO_SIMD)
 # ifdef __XEN__
 #  include <asm/xstate.h>
-#  define FXSAVE_AREA current->arch.fpu_ctxt
+#  define FXSAVE_AREA ((void *)&current->arch.xsave_area->fpu_sse)
 # else
 #  define FXSAVE_AREA get_fpu_save_area()
 # endif
diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index 57a0749f0d..af9e345a7a 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -508,9 +508,15 @@ int xstate_alloc_save_area(struct vcpu *v)
     unsigned int size;
 
     if ( !cpu_has_xsave )
-        return 0;
-
-    if ( !is_idle_vcpu(v) || !cpu_has_xsavec )
+    {
+        /*
+         * On non-XSAVE systems, we allocate an XSTATE buffer for simplicity.
+         * XSTATE is backwards compatible to FXSAVE, and only one cacheline
+         * larger.
+         */
+        size = XSTATE_AREA_MIN_SIZE;
+    }
+    else if ( !is_idle_vcpu(v) || !cpu_has_xsavec )
     {
         size = xsave_cntxt_size;
         BUG_ON(size < XSTATE_AREA_MIN_SIZE);
--
generated by git-patchbot for /home/xen/git/xen.git#staging



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.