linux-kernel - [RFC PATCH v5 10/16] KVM: x86/tdp_mmu: Allocate private page table for large page split

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Date:   Mon, 16 Oct 2023 09:21:01 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com
Subject: [RFC PATCH v5 10/16] KVM: x86/tdp_mmu: Allocate private page table for large page split

From: Isaku Yamahata <isaku.yamahata@...el.com>

Make tdp_mmu_alloc_sp_split() aware of private page table.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/mmu/mmu_internal.h | 14 ++++++++++++++
 arch/x86/kvm/mmu/tdp_mmu.c      |  8 ++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 908504bcc2cd..641d4e777b73 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -203,6 +203,15 @@ static inline void kvm_mmu_alloc_private_spt(struct kvm_vcpu *vcpu, struct kvm_m
 	}
 }
 
+static inline int kvm_alloc_private_spt_for_split(struct kvm_mmu_page *sp, gfp_t gfp)
+{
+	gfp &= ~__GFP_ZERO;
+	sp->private_spt = (void *)__get_free_page(gfp);
+	if (!sp->private_spt)
+		return -ENOMEM;
+	return 0;
+}
+
 static inline void kvm_mmu_free_private_spt(struct kvm_mmu_page *sp)
 {
 	if (sp->private_spt)
@@ -231,6 +240,11 @@ static inline void kvm_mmu_alloc_private_spt(struct kvm_vcpu *vcpu, struct kvm_m
 {
 }
 
+static inline int kvm_alloc_private_spt_for_split(struct kvm_mmu_page *sp, gfp_t gfp)
+{
+	return -ENOMEM;
+}
+
 static inline void kvm_mmu_free_private_spt(struct kvm_mmu_page *sp)
 {
 }
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 012f270cfb6f..75a2fec7a3fa 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1706,8 +1706,12 @@ static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(gfp_t gfp, union kvm_mm
 
 	sp->role = role;
 	sp->spt = (void *)__get_free_page(gfp);
-	/* TODO: large page support for private GPA. */
-	WARN_ON_ONCE(kvm_mmu_page_role_is_private(role));
+	if (kvm_mmu_page_role_is_private(role)) {
+		if (kvm_alloc_private_spt_for_split(sp, gfp)) {
+			free_page((unsigned long)sp->spt);
+			sp->spt = NULL;
+		}
+	}
 	if (!sp->spt) {
 		kmem_cache_free(mmu_page_header_cache, sp);
 		return NULL;
-- 
2.25.1