Re: [PATCH] KVM: x86: use correct APIC ID on x2APIC transition

[Paolo Bonzini]

On 22/05/2015 18:45, Radim Krčmář wrote:
 SDM April 2015, 10.12.5 State Changes From xAPIC Mode to x2APIC Mode
 • Any APIC ID value written to the memory-mapped local APIC ID register
   is not preserved.
 
 Fix it by sourcing vcpu_id (= initial APIC ID) instead of memory-mapped
 APIC ID.  Proper use of apic functions would result in two calls to
 recalculate_apic_map(), so this patch makes a new helper.
 
 Signed-off-by: Radim Krčmář rkrc...@redhat.com
 ---
  arch/x86/kvm/lapic.c | 13 ++---
  1 file changed, 10 insertions(+), 3 deletions(-)
 
 diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
 index dc5b57bb1f76..c2a7d8a7a414 100644
 --- a/arch/x86/kvm/lapic.c
 +++ b/arch/x86/kvm/lapic.c
 @@ -240,6 +240,15 @@ static inline void kvm_apic_set_ldr(struct kvm_lapic 
 *apic, u32 id)
   recalculate_apic_map(apic-vcpu-kvm);
  }
  
 +static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u8 id)
 +{
 + u32 ldr = ((id  4)  16) | (1  (id  0xf));
 +
 + apic_set_reg(apic, APIC_ID, id  24);
 + apic_set_reg(apic, APIC_LDR, ldr);
 + recalculate_apic_map(apic-vcpu-kvm);
 +}
 +
  static inline int apic_lvt_enabled(struct kvm_lapic *apic, int lvt_type)
  {
   return !(kvm_apic_get_reg(apic, lvt_type)  APIC_LVT_MASKED);
 @@ -1538,9 +1547,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 
 value)
  
   if ((old_value ^ value)  X2APIC_ENABLE) {
   if (value  X2APIC_ENABLE) {
 - u32 id = kvm_apic_id(apic);
 - u32 ldr = ((id  4)  16) | (1  (id  0xf));
 - kvm_apic_set_ldr(apic, ldr);
 + kvm_apic_set_x2apic_id(apic, vcpu-vcpu_id);
   kvm_x86_ops-set_virtual_x2apic_mode(vcpu, true);
   } else
   kvm_x86_ops-set_virtual_x2apic_mode(vcpu, false);
 

Applied, thanks.

Paolo
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[PATCH] KVM: x86: use correct APIC ID on x2APIC transition

[Radim Krčmář]

SDM April 2015, 10.12.5 State Changes From xAPIC Mode to x2APIC Mode
• Any APIC ID value written to the memory-mapped local APIC ID register
  is not preserved.

Fix it by sourcing vcpu_id (= initial APIC ID) instead of memory-mapped
APIC ID.  Proper use of apic functions would result in two calls to
recalculate_apic_map(), so this patch makes a new helper.

Signed-off-by: Radim Krčmář rkrc...@redhat.com
---
 arch/x86/kvm/lapic.c | 13 ++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index dc5b57bb1f76..c2a7d8a7a414 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -240,6 +240,15 @@ static inline void kvm_apic_set_ldr(struct kvm_lapic 
*apic, u32 id)
recalculate_apic_map(apic-vcpu-kvm);
 }
 
+static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u8 id)
+{
+   u32 ldr = ((id  4)  16) | (1  (id  0xf));
+
+   apic_set_reg(apic, APIC_ID, id  24);
+   apic_set_reg(apic, APIC_LDR, ldr);
+   recalculate_apic_map(apic-vcpu-kvm);
+}
+
 static inline int apic_lvt_enabled(struct kvm_lapic *apic, int lvt_type)
 {
return !(kvm_apic_get_reg(apic, lvt_type)  APIC_LVT_MASKED);
@@ -1538,9 +1547,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 
if ((old_value ^ value)  X2APIC_ENABLE) {
if (value  X2APIC_ENABLE) {
-   u32 id = kvm_apic_id(apic);
-   u32 ldr = ((id  4)  16) | (1  (id  0xf));
-   kvm_apic_set_ldr(apic, ldr);
+   kvm_apic_set_x2apic_id(apic, vcpu-vcpu_id);
kvm_x86_ops-set_virtual_x2apic_mode(vcpu, true);
} else
kvm_x86_ops-set_virtual_x2apic_mode(vcpu, false);
-- 
2.4.1

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