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[PATCH 2/3] KVM/MIPS32: Wrap calls to gfn_to_pfn() with srcu_read_lock/u

To: kvm@vger.kernel.org
Subject: [PATCH 2/3] KVM/MIPS32: Wrap calls to gfn_to_pfn() with srcu_read_lock/unlock()
From: Sanjay Lal <sanjayl@kymasys.com>
Date: Fri, 17 May 2013 14:25:11 -0700
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org, gleb@redhat.com, mtosatti@redhat.com, Sanjay Lal <sanjayl@kymasys.com>
In-reply-to: <1368825912-23562-1-git-send-email-sanjayl@kymasys.com>
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- As suggested by Gleb, wrap calls to gfn_to_pfn() with srcu_read_lock/unlock().
  Memory slots should be acccessed from a SRCU read section.
- kvm_mips_map_page() now returns an error code to it's callers, instead of 
calling panic()
 if it cannot find a mapping for a particular gfn.

Signed-off-by: Sanjay Lal <sanjayl@kymasys.com>
---
 arch/mips/kvm/kvm_tlb.c | 36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/arch/mips/kvm/kvm_tlb.c b/arch/mips/kvm/kvm_tlb.c
index 89511a9..ab2e9b0 100644
--- a/arch/mips/kvm/kvm_tlb.c
+++ b/arch/mips/kvm/kvm_tlb.c
@@ -16,7 +16,10 @@
 #include <linux/mm.h>
 #include <linux/delay.h>
 #include <linux/module.h>
+#include <linux/bootmem.h>
 #include <linux/kvm_host.h>
+#include <linux/srcu.h>
+
 
 #include <asm/cpu.h>
 #include <asm/bootinfo.h>
@@ -169,21 +172,27 @@ void kvm_mips_dump_shadow_tlbs(struct kvm_vcpu *vcpu)
        }
 }
 
-static void kvm_mips_map_page(struct kvm *kvm, gfn_t gfn)
+static int kvm_mips_map_page(struct kvm *kvm, gfn_t gfn)
 {
+       int srcu_idx, err = 0;
        pfn_t pfn;
 
        if (kvm->arch.guest_pmap[gfn] != KVM_INVALID_PAGE)
-               return;
+               return 0;
 
+        srcu_idx = srcu_read_lock(&kvm->srcu);
        pfn = kvm_mips_gfn_to_pfn(kvm, gfn);
 
        if (kvm_mips_is_error_pfn(pfn)) {
-               panic("Couldn't get pfn for gfn %#" PRIx64 "!\n", gfn);
+               kvm_err("Couldn't get pfn for gfn %#" PRIx64 "!\n", gfn);
+               err = -EFAULT;
+               goto out;
        }
 
        kvm->arch.guest_pmap[gfn] = pfn;
-       return;
+out:
+       srcu_read_unlock(&kvm->srcu, srcu_idx);
+       return err;
 }
 
 /* Translate guest KSEG0 addresses to Host PA */
@@ -207,7 +216,10 @@ unsigned long kvm_mips_translate_guest_kseg0_to_hpa(struct 
kvm_vcpu *vcpu,
                        gva);
                return KVM_INVALID_PAGE;
        }
-       kvm_mips_map_page(vcpu->kvm, gfn);
+
+       if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
+               return KVM_INVALID_ADDR;
+
        return (kvm->arch.guest_pmap[gfn] << PAGE_SHIFT) + offset;
 }
 
@@ -310,8 +322,11 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
        even = !(gfn & 0x1);
        vaddr = badvaddr & (PAGE_MASK << 1);
 
-       kvm_mips_map_page(vcpu->kvm, gfn);
-       kvm_mips_map_page(vcpu->kvm, gfn ^ 0x1);
+       if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
+               return -1;
+
+       if (kvm_mips_map_page(vcpu->kvm, gfn ^ 0x1) < 0)
+               return -1;
 
        if (even) {
                pfn0 = kvm->arch.guest_pmap[gfn];
@@ -389,8 +404,11 @@ kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
                pfn0 = 0;
                pfn1 = 0;
        } else {
-               kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo0) >> 
PAGE_SHIFT);
-               kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo1) >> 
PAGE_SHIFT);
+               if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo0) 
>> PAGE_SHIFT) < 0)
+                       return -1;
+
+               if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo1) 
>> PAGE_SHIFT) < 0)
+                       return -1;
 
                pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo0) 
>> PAGE_SHIFT];
                pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo1) 
>> PAGE_SHIFT];
-- 
1.7.11.3


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