[PATCH v13 10/21] KVM: x86/xen: separate initialization of shared_info cache and content

Paul Durrant
2024-02-15T15:44:35Z

From: Paul Durrant <pdurrant@amazon.com>

A subsequent patch will allow shared_info to be initialized using either a
GPA or a user-space (i.e. VMM) HVA. To make that patch cleaner, separate
the initialization of the shared_info content from the activation of the
pfncache.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: x86@kernel.org

v13:
- Patch title change.

v11:
- Fix accidental regression from commit 5d6d6a7d7e66a ("KVM: x86: Refine
calculation of guest wall clock to use a single TSC read").

v10:
- New in this version.
---
arch/x86/kvm/xen.c | 55 +++++++++++++++++++++++++++-------------------
1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index e90464225467..031e98d88ba2 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -34,41 +34,32 @@ static bool kvm_xen_hcall_evtchn_send(struct kvm_vcpu *vcpu, u64 param, u64 *r);

DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ);

-static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
+static int kvm_xen_shared_info_init(struct kvm *kvm)
{
struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
struct pvclock_wall_clock *wc;
- gpa_t gpa = gfn_to_gpa(gfn);
u32 *wc_sec_hi;
u32 wc_version;
u64 wall_nsec;
int ret = 0;
int idx = srcu_read_lock(&kvm->srcu);

- if (gfn == KVM_XEN_INVALID_GFN) {
- kvm_gpc_deactivate(gpc);
- goto out;
- }
+ read_lock_irq(&gpc->lock);
+ while (!kvm_gpc_check(gpc, PAGE_SIZE)) {
+ read_unlock_irq(&gpc->lock);

- do {
- ret = kvm_gpc_activate(gpc, gpa, PAGE_SIZE);
+ ret = kvm_gpc_refresh(gpc, PAGE_SIZE);
if (ret)
goto out;

- /*
- * This code mirrors kvm_write_wall_clock() except that it writes
- * directly through the pfn cache and doesn't mark the page dirty.
- */
- wall_nsec = kvm_get_wall_clock_epoch(kvm);
-
- /* It could be invalid again already, so we need to check */
read_lock_irq(&gpc->lock);
+ }

- if (gpc->valid)
- break;
-
- read_unlock_irq(&gpc->lock);
- } while (1);
+ /*
+ * This code mirrors kvm_write_wall_clock() except that it writes
+ * directly through the pfn cache and doesn't mark the page dirty.
+ */
+ wall_nsec = kvm_get_wall_clock_epoch(kvm);

/* Paranoia checks on the 32-bit struct layout */
BUILD_BUG_ON(offsetof(struct compat_shared_info, wc) != 0x900);
@@ -639,12 +630,30 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
}
break;

- case KVM_XEN_ATTR_TYPE_SHARED_INFO:
+ case KVM_XEN_ATTR_TYPE_SHARED_INFO: {
+ int idx;
+
mutex_lock(&kvm->arch.xen.xen_lock);
- r = kvm_xen_shared_info_init(kvm, data->u.shared_info.gfn);
+
+ idx = srcu_read_lock(&kvm->srcu);
+
+ if (data->u.shared_info.gfn == KVM_XEN_INVALID_GFN) {
+ kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
+ r = 0;
+ } else {
+ r = kvm_gpc_activate(&kvm->arch.xen.shinfo_cache,
+ gfn_to_gpa(data->u.shared_info.gfn),
+ PAGE_SIZE);
+ }
+
+ srcu_read_unlock(&kvm->srcu, idx);
+
+ if (!r && kvm->arch.xen.shinfo_cache.active)
+ r = kvm_xen_shared_info_init(kvm);
+
mutex_unlock(&kvm->arch.xen.xen_lock);
break;
-
+ }
case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR:
if (data->u.vector && data->u.vector < 0x10)
r = -EINVAL;
--
2.39.2