[RFC PATCH 11/73] KVM: x86: Implement gpc refresh for guest usage

Lai Jiangshan
2024-02-26T14:35:13Z

From: Hou Wenlong <houwenlong.hwl@antgroup.com>

PVM uses pfncache to share the PVCS structure between the guest and
host. The flag of pfncache of PVCS is initialized as
KVM_GUEST_AND_HOST_USE_PFN because the PVCS is used inside the
vcpu_run() callback, even in the switcher, where the vcpu is in guest
mode. However, there is no real usage for GUEST_USE_PFN, so the request
in mmu_notifier only kicks the vcpu out of guest mode and no refresh is
done before the next vcpu_run(). Therefore, a new request type is
introduced to request the refresh, and a new callback is used to service
the request.

Suggested-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
arch/x86/include/asm/kvm-x86-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 3 +++
arch/x86/kvm/mmu/mmu.c | 1 +
arch/x86/kvm/x86.c | 3 +++
include/linux/kvm_host.h | 10 ++++++++++
virt/kvm/pfncache.c | 2 +-
6 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 32e5473b499d..0d9b21988943 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -94,6 +94,7 @@ KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
KVM_X86_OP(load_mmu_pgd)
KVM_X86_OP_OPTIONAL_RET0(disallowed_va)
+KVM_X86_OP_OPTIONAL(vcpu_gpc_refresh);
KVM_X86_OP(has_wbinvd_exit)
KVM_X86_OP(get_l2_tsc_offset)
KVM_X86_OP(get_l2_tsc_multiplier)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d17d85106d6f..9223d34cb8e3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1683,6 +1683,8 @@ struct kvm_x86_ops {

bool (*disallowed_va)(struct kvm_vcpu *vcpu, u64 la);

+ void (*vcpu_gpc_refresh)(struct kvm_vcpu *vcpu);
+
bool (*has_wbinvd_exit)(void);

u64 (*get_l2_tsc_offset)(struct kvm_vcpu *vcpu);
@@ -1839,6 +1841,7 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
}

#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
+#define __KVM_HAVE_GUEST_USE_PFN_USAGE

#define kvm_arch_pmi_in_guest(vcpu) \
((vcpu) && (vcpu)->arch.handling_intr_from_guest)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 80406666d7da..7bd88f7ace51 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6741,6 +6741,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
kvm_mmu_zap_all_fast(kvm);
+ kvm_make_all_cpus_request(kvm, KVM_REQ_GPC_REFRESH);
}

void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index be8fdae942d1..89bf368085a9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10786,6 +10786,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)

if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING, vcpu))
static_call(kvm_x86_update_cpu_dirty_logging)(vcpu);
+
+ if (kvm_check_request(KVM_REQ_GPC_REFRESH, vcpu))
+ static_call_cond(kvm_x86_vcpu_gpc_refresh)(vcpu);
}

if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4944136efaa2..b7c490e74704 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -167,6 +167,7 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_VM_DEAD (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_UNBLOCK 2
#define KVM_REQ_DIRTY_RING_SOFT_FULL 3
+#define KVM_REQ_GPC_REFRESH (5 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQUEST_ARCH_BASE 8

/*
@@ -1367,6 +1368,15 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
*/
void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);

+static inline unsigned int kvm_gpc_refresh_request(void)
+{
+#ifdef __KVM_HAVE_GUEST_USE_PFN_USAGE
+ return KVM_REQ_GPC_REFRESH;
+#else
+ return KVM_REQ_OUTSIDE_GUEST_MODE;
+#endif
+}
+
void kvm_sigset_activate(struct kvm_vcpu *vcpu);
void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 2d6aba677830..f7b7a2f75ec7 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -59,7 +59,7 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start,
* KVM needs to ensure the vCPU is fully out of guest context
* before allowing the invalidation to continue.
*/
- unsigned int req = KVM_REQ_OUTSIDE_GUEST_MODE;
+ unsigned int req = kvm_gpc_refresh_request();
bool called;

/*
--
2.19.1.6.gb485710b