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

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Message-ID: <20150605151337.GA16327@potion.brq.redhat.com>
Date:	Fri, 5 Jun 2015 17:13:37 +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 14:46+0200, Paolo Bonzini:
> On 05/06/2015 14:10, Radim Krčmář wrote:
> > +		ret = __kvm_write_guest_page(__gfn_to_memslot(slots, gfn), gfn,
> > +				data, offset, seg);
> 
> Even better, let's pass memslots to all the __ functions.

Yeah, while scoping it, I noticed a bug in the series ...
makes me wish that C had a useful type system.

A quick fix would be to replace gpa with gfn in calls to
__kvm_read_guest_atomic().  I presume you'd prefer a new patch to
rebasing, so it's below.

---
KVM: fix gpa/gfn mixup in __kvm_read_guest_atomic

Refactoring passed gpa instead of gfn to __kvm_read_guest_atomic.
While at it, lessen code duplication by extracting slots earlier.

Fixes: 841509f38372 ("KVM: add vcpu-specific functions to read/write/translate GFNs")
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 virt/kvm/kvm_main.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 10ae7e348dcc..4fa1edc34630 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1645,11 +1645,14 @@ int kvm_vcpu_read_guest(struct kvm_vcpu *vcpu, gpa_t gpa, void *data, unsigned l
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest);
 
-static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
-			           void *data, int offset, unsigned long len)
+static int __kvm_read_guest_atomic(struct kvm_memslots *slots, gpa_t gpa,
+			           void *data, unsigned long len)
 {
 	int r;
 	unsigned long addr;
+	gfn_t gfn = gpa >> PAGE_SHIFT;
+	struct kvm_memory_slot *slot = __gfn_to_memslot(slots, gfn);
+	int offset = offset_in_page(gpa);
 
 	addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
 	if (kvm_is_error_hva(addr))
@@ -1665,22 +1668,18 @@ static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
 int kvm_read_guest_atomic(struct kvm *kvm, gpa_t gpa, void *data,
 			  unsigned long len)
 {
-	gfn_t gfn = gpa >> PAGE_SHIFT;
-	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
-	int offset = offset_in_page(gpa);
+	struct kvm_memslots *slots = kvm_memslots(kvm);
 
-	return __kvm_read_guest_atomic(slot, gpa, data, offset, len);
+	return __kvm_read_guest_atomic(slots, gpa, data, len);
 }
 EXPORT_SYMBOL_GPL(kvm_read_guest_atomic);
 
 int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
 			       void *data, unsigned long len)
 {
-	gfn_t gfn = gpa >> PAGE_SHIFT;
-	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
-	int offset = offset_in_page(gpa);
+	struct kvm_memslots *slots = kvm_vcpu_memslots(vcpu);
 
-	return __kvm_read_guest_atomic(slot, gpa, data, offset, len);
+	return __kvm_read_guest_atomic(slots, gpa, data, len);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);
 
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