[Xen-devel] [PATCH V7 3/3] x86/xsaves: ebx may return wrong value using CPUID eax=0xdh, ecx =1

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

From: Shuai Ruan <shuai.ruan@xxxxxxxxx>

Refer to SDM 13.4.3 Extended Region of an XSAVE Area. The value return
by ecx[1] with cpuid function 0xdh and sub-fucntion i (i>1) indicates
the alignment of the state component i when the compacted format of the
extended region of an xsave area is used.

So when hvm/pv guest using CPUID eax=0xdh,ecx=1 to get the size of area
used for compacted format, we need to take alignment into consideration.

tools side is fixed by
"tools/libxc: Calculate xstate cpuid leaf from guest information"
by Andrew Cooper

Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxx>
---
v2: Address comments by Jan:
1. take alignment into consideration in pv_cpuid.
2. fix coding style issues

 xen/arch/x86/hvm/hvm.c       |  6 +++++-
 xen/arch/x86/traps.c         | 12 ++++++++++++
 xen/arch/x86/xstate.c        |  2 +-
 xen/include/asm-x86/xstate.h |  1 +
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 5aef3cb..c6cd4fb 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4743,14 +4743,18 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, 
unsigned int *ebx,
         }
         if ( count == 1 )
         {
-            if ( cpu_has_xsaves && cpu_has_vmx_xsaves )
+            if ( (cpu_has_xsaves && cpu_has_vmx_xsaves) || cpu_has_xsavec )
             {
                 *ebx = XSTATE_AREA_MIN_SIZE;
                 if ( v->arch.xcr0 | v->arch.hvm_vcpu.msr_xss )
                     for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
                         if ( (v->arch.xcr0 | v->arch.hvm_vcpu.msr_xss) &
                              (1ULL << sub_leaf) )
+                        {
+                            if ( test_bit(sub_leaf, &xstate_align) )
+                                *ebx = ROUNDUP(*ebx, 64);
                             *ebx += xstate_sizes[sub_leaf];
+                        }
             }
             else
                 *ebx = *ecx = *edx = 0;
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 6fbb1cf..8694da6 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1020,6 +1020,18 @@ void pv_cpuid(struct cpu_user_regs *regs)
             a &= 
(boot_cpu_data.x86_capability[cpufeat_word(X86_FEATURE_XSAVEOPT)] &
                   ~cpufeat_mask(X86_FEATURE_XSAVES));
             b = c = d = 0;
+            if ( cpu_has_xsavec )
+            {
+                b = XSTATE_AREA_MIN_SIZE;
+                if ( curr->arch.xcr0 )
+                    for( subleaf = 2; subleaf < 63; subleaf++ )
+                        if ( (1ULL << subleaf) & curr->arch.xcr0 )
+                        {
+                            if ( test_bit(subleaf, &xstate_align) )
+                                b = ROUNDUP(b, 64);
+                            b += xstate_sizes[subleaf];
+                        }
+            }
             break;
         }
         break;
diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index f4ea54d..850b778 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -26,7 +26,7 @@ u64 __read_mostly xfeature_mask;
 
 static unsigned int *__read_mostly xstate_offsets;
 unsigned int *__read_mostly xstate_sizes;
-static u64 __read_mostly xstate_align;
+u64 __read_mostly xstate_align;
 static unsigned int __read_mostly xstate_features;
 
 static uint32_t __read_mostly mxcsr_mask = 0x0000ffbf;
diff --git a/xen/include/asm-x86/xstate.h b/xen/include/asm-x86/xstate.h
index 91d1c39..535443a 100644
--- a/xen/include/asm-x86/xstate.h
+++ b/xen/include/asm-x86/xstate.h
@@ -50,6 +50,7 @@
 #define XSTATE_ALIGN64 (1U << 1)
 
 extern u64 xfeature_mask;
+extern u64 xstate_align;
 extern unsigned int *xstate_sizes;
 
 /* extended state save area */
-- 
1.9.1


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