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Code Issues Releases Wiki Activity

KVM: xen: do not use struct gfn_to_hva_cache

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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>
This commit is contained in:
Paolo Bonzini 2021-08-04 12:48:41 -04:00
parent e79f49c37c
commit 319afe6856
4 changed files with 19 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
arch/x86/include/asm/kvm_host.h
View file

@ -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 {

1
arch/x86/kvm/x86.c
View file

@ -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);
}

23
arch/x86/kvm/xen.c
View file

@ -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)

5
arch/x86/kvm/xen.h
View file

@ -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)
{
}