KVM: xen: do not use struct gfn_to_hva_cache

gfn_to_hva_cache is not thread-safe, so it is usually used only within
a vCPU (whose code is protected by vcpu->mutex).  The Xen interface
implementation has such a cache in kvm->arch, but it is not really
used except to store the location of the shared info page.  Replace
shinfo_set and shinfo_cache with just the value that is passed via
KVM_XEN_ATTR_TYPE_SHARED_INFO; the only complication is that the
initialization value is not zero anymore and therefore kvm_xen_init_vm
needs to be introduced.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a079880d4cd5fec2ca91b4164908543236d44ac5..6a73ff7db5f98235409c335a4d5e3b0dc4b3c006 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1003,9 +1003,8 @@ struct msr_bitmap_range {
 /* Xen emulation context */
 struct kvm_xen {
        bool long_mode;
-       bool shinfo_set;
        u8 upcall_vector;
-       struct gfn_to_hva_cache shinfo_cache;
+       gfn_t shinfo_gfn;
 };
 
 enum kvm_irqchip_mode {

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 348452bb16bc62369fc7436c8f70eb70933db9ea..3cedc7cc132aba9d797348505ca223bc103af3f4 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11162,6 +11162,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
        kvm_hv_init_vm(kvm);
        kvm_page_track_init(kvm);
        kvm_mmu_init_vm(kvm);
+       kvm_xen_init_vm(kvm);
 
        return static_call(kvm_x86_vm_init)(kvm);
 }

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index ae17250e1efe0a1e5e78d8ffc5fd3b01ab4af94c..9ea9c3dabe3718bd9d47eaaad96f855829e2d77e 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -25,15 +25,14 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 {
        gpa_t gpa = gfn_to_gpa(gfn);
        int wc_ofs, sec_hi_ofs;
-       int ret;
+       int ret = 0;
        int idx = srcu_read_lock(&kvm->srcu);
 
-       ret = kvm_gfn_to_hva_cache_init(kvm, &kvm->arch.xen.shinfo_cache,
-                                       gpa, PAGE_SIZE);
-       if (ret)
+       if (kvm_is_error_hva(gfn_to_hva(kvm, gfn))) {
+               ret = -EFAULT;
                goto out;
-
-       kvm->arch.xen.shinfo_set = true;
+       }
+       kvm->arch.xen.shinfo_gfn = gfn;
 
        /* Paranoia checks on the 32-bit struct layout */
        BUILD_BUG_ON(offsetof(struct compat_shared_info, wc) != 0x900);
@@ -245,7 +244,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
        case KVM_XEN_ATTR_TYPE_SHARED_INFO:
                if (data->u.shared_info.gfn == GPA_INVALID) {
-                       kvm->arch.xen.shinfo_set = false;
+                       kvm->arch.xen.shinfo_gfn = GPA_INVALID;
                        r = 0;
                        break;
                }
@@ -283,10 +282,7 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
                break;
 
        case KVM_XEN_ATTR_TYPE_SHARED_INFO:
-               if (kvm->arch.xen.shinfo_set)
-                       data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_cache.gpa);
-               else
-                       data->u.shared_info.gfn = GPA_INVALID;
+               data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_gfn);
                r = 0;
                break;
 
@@ -646,6 +642,11 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc)
        return 0;
 }
 
+void kvm_xen_init_vm(struct kvm *kvm)
+{
+       kvm->arch.xen.shinfo_gfn = GPA_INVALID;
+}
+
 void kvm_xen_destroy_vm(struct kvm *kvm)
 {
        if (kvm->arch.xen_hvm_config.msr)

diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 463a7844a8caeb42e2e37a323ae8bcb2f40ef1d9..cc0cf5f37450b0e0c908b4d0ae6db3a5d3339d9a 100644 (file)
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -21,6 +21,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data);
 int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc);
+void kvm_xen_init_vm(struct kvm *kvm);
 void kvm_xen_destroy_vm(struct kvm *kvm);
 
 static inline bool kvm_xen_msr_enabled(struct kvm *kvm)
@@ -50,6 +51,10 @@ static inline int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
        return 1;
 }
 
+static inline void kvm_xen_init_vm(struct kvm *kvm)
+{
+}
+
 static inline void kvm_xen_destroy_vm(struct kvm *kvm)
 {
 }