linux-kernel - Re: [PATCH v2 07/13] KVM: add vcpu-specific functions to read/write/translate GFNs

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Date:	Fri, 5 Jun 2015 14:10:52 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	guangrong.xiao@...ux.intel.com, bdas@...hat.com
Subject: Re: [PATCH v2 07/13] KVM: add vcpu-specific functions to
 read/write/translate GFNs

2015-06-05 12:26+0200, Paolo Bonzini:
> On 29/05/2015 21:23, Radim Krčmář wrote:
>>> > +int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
>>> > +		         unsigned long len)
>>> > +{
| [...]
>>> > +}
>> (There is no need to pass vcpu, and kvm, in this API.
> 
> How so?  A single kvm_vcpu_write_guest can cross multiple slots.

I meant passing 'struct kvm_memslots *' instead and as soon as possible,
which would still allow more slots.  Something like this hunk:

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 10ae7e348dcc..8c6d84c12f18 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1718,8 +1718,8 @@ int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);
 
-int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
-		    unsigned long len)
+static int __kvm_write_guest(struct kvm_memslots *slots, gpa_t gpa, const void *data,
+		unsigned long len)
 {
 	gfn_t gfn = gpa >> PAGE_SHIFT;
 	int seg;
@@ -1727,7 +1727,8 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
 	int ret;
 
 	while ((seg = next_segment(len, offset)) != 0) {
-		ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
+		ret = __kvm_write_guest_page(__gfn_to_memslot(slots, gfn), gfn,
+				data, offset, seg);
 		if (ret < 0)
 			return ret;
 		offset = 0;
@@ -1737,26 +1738,18 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
 	}
 	return 0;
 }
+
+int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
+		    unsigned long len)
+{
+	return __kvm_write_guest(kvm_memslots(kvm), gpa, data, len);
+}
 EXPORT_SYMBOL_GPL(kvm_write_guest);
 
 int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
 		         unsigned long len)
 {
-	gfn_t gfn = gpa >> PAGE_SHIFT;
-	int seg;
-	int offset = offset_in_page(gpa);
-	int ret;
-
-	while ((seg = next_segment(len, offset)) != 0) {
-		ret = kvm_vcpu_write_guest_page(vcpu, gfn, data, offset, seg);
-		if (ret < 0)
-			return ret;
-		offset = 0;
-		len -= seg;
-		data += seg;
-		++gfn;
-	}
-	return 0;
+	return __kvm_write_guest(kvm_vcpu_memslots(vcpu), gpa, data, len);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest);
 
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