linux-kernel - [PATCH 05/16] KVM: arm64: Accept page ranges in pkvm share hypercall

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Message-Id: <20211013155831.943476-6-qperret@google.com>
Date:   Wed, 13 Oct 2021 16:58:20 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Fuad Tabba <tabba@...gle.com>,
        David Brazdil <dbrazdil@...gle.com>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: [PATCH 05/16] KVM: arm64: Accept page ranges in pkvm share hypercall

The recently reworked do_share() infrastructure for the nVHE protected
mode allows to transition the state of a range of pages 'atomically'.
This is preferable over single-page sharing when e.g. mapping guest
vCPUs in the hypervisor stage-1 as the permission checks and page-table
modifications for the entire range are done in a single critical
section. This means there is no need for the host the handle e.g. only
half of a vCPU being successfully shared with the hypervisor.

So, make use of that feature in the __pkvm_host_share_hyp() hypercall by
allowing to specify a pfn range.

Signed-off-by: Quentin Perret <qperret@...gle.com>
---
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  2 +-
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            |  3 ++-
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         |  4 +--
 arch/arm64/kvm/mmu.c                          | 25 +++++++------------
 4 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index 56445586c755..9c02abe92e0a 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -54,7 +54,7 @@ extern struct host_kvm host_kvm;
 extern const u8 pkvm_hyp_id;
 
 int __pkvm_prot_finalize(void);
-int __pkvm_host_share_hyp(u64 pfn);
+int __pkvm_host_share_hyp(u64 pfn, u64 nr_pages);
 
 bool addr_is_memory(phys_addr_t phys);
 int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 2da6aa8da868..f78bec2b9dd4 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -143,8 +143,9 @@ static void handle___pkvm_cpu_set_vector(struct kvm_cpu_context *host_ctxt)
 static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(u64, pfn, host_ctxt, 1);
+	DECLARE_REG(u64, nr_pages, host_ctxt, 2);
 
-	cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn);
+	cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn, nr_pages);
 }
 
 static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 6983b83f799f..909e60f71b06 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -671,14 +671,14 @@ static int do_share(struct pkvm_mem_share *share)
 	return ret;
 }
 
-int __pkvm_host_share_hyp(u64 pfn)
+int __pkvm_host_share_hyp(u64 pfn, u64 nr_pages)
 {
 	int ret;
 	u64 host_addr = hyp_pfn_to_phys(pfn);
 	u64 hyp_addr = (u64)__hyp_va(host_addr);
 	struct pkvm_mem_share share = {
 		.tx	= {
-			.nr_pages	= 1,
+			.nr_pages	= nr_pages,
 			.initiator	= {
 				.id	= PKVM_ID_HOST,
 				.addr	= host_addr,
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f80673e863ac..bc9865a8c988 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -281,30 +281,23 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
 	}
 }
 
-static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
-{
-	phys_addr_t addr;
-	int ret;
-
-	for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
-		ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
-					__phys_to_pfn(addr));
-		if (ret)
-			return ret;
-	}
-
-	return 0;
-}
-
 int kvm_share_hyp(void *from, void *to)
 {
+	phys_addr_t start, end;
+	u64 nr_pages;
+
 	if (is_kernel_in_hyp_mode())
 		return 0;
 
 	if (kvm_host_owns_hyp_mappings())
 		return create_hyp_mappings(from, to, PAGE_HYP);
 
-	return pkvm_share_hyp(kvm_kaddr_to_phys(from), kvm_kaddr_to_phys(to));
+	start = ALIGN_DOWN(kvm_kaddr_to_phys(from), PAGE_SIZE);
+	end = PAGE_ALIGN(kvm_kaddr_to_phys(to));
+	nr_pages = (end - start) >> PAGE_SHIFT;
+
+	return kvm_call_hyp_nvhe(__pkvm_host_share_hyp, __phys_to_pfn(start),
+				 nr_pages);
 }
 
 /**
-- 
2.33.0.882.g93a45727a2-goog