Re: [PATCH 07/11] Retry fault before vmentry

From: Avi Kivity
Date: Mon Nov 02 2009 - 08:03:44 EST

On 11/01/2009 01:56 PM, Gleb Natapov wrote:
When page is swapped in it is mapped into guest memory only after guest
tries to access it again and generate another fault. To save this fault
we can map it immediately since we know that guest is going to access
the page.

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 9fe2ecd..b1fe61f 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -375,7 +375,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
* Returns: 1 if we need to emulate the instruction, 0 otherwise, or
* a negative value on error.
-static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
+static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t cr3, gva_t addr,
u32 error_code)
int write_fault = error_code& PFERR_WRITE_MASK;
@@ -388,6 +388,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
pfn_t pfn;
int level = PT_PAGE_TABLE_LEVEL;
unsigned long mmu_seq;
+ gpa_t curr_cr3 = vcpu->arch.cr3;

pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
kvm_mmu_audit(vcpu, "pre page fault");
@@ -396,6 +397,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
if (r)
return r;

+ if (curr_cr3 != cr3) {
+ vcpu->arch.cr3 = cr3;
+ paging_new_cr3(vcpu);
+ if (kvm_mmu_reload(vcpu))
+ goto switch_cr3;
+ }

This is a little frightening. I can't put my finger on anything though. But playing with cr3 under the guest's feet worries me.

error compiling committee.c: too many arguments to function

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