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Date: Tue, 5 Oct 2010 12:54:09 -0300
From: Marcelo Tosatti <mtosatti@...hat.com>
To: Gleb Natapov <gleb@...hat.com>
Cc: kvm@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, avi@...hat.com, mingo@...e.hu,
a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
riel@...hat.com, cl@...ux-foundation.org
Subject: Re: [PATCH v6 03/12] Retry fault before vmentry
On Mon, Oct 04, 2010 at 05:56:25PM +0200, 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. Do it only when tdp is enabled for now. Shadow paging case is
> more complicated. CR[034] and EFER registers should be switched before
> doing mapping and then switched back.
>
> Acked-by: Rik van Riel <riel@...hat.com>
> Signed-off-by: Gleb Natapov <gleb@...hat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 4 +++-
> arch/x86/kvm/mmu.c | 16 ++++++++--------
> arch/x86/kvm/paging_tmpl.h | 6 +++---
> arch/x86/kvm/x86.c | 7 +++++++
> virt/kvm/async_pf.c | 2 ++
> 5 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5f154d3..b9f263e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -240,7 +240,7 @@ struct kvm_mmu {
> void (*new_cr3)(struct kvm_vcpu *vcpu);
> void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long root);
> unsigned long (*get_cr3)(struct kvm_vcpu *vcpu);
> - int (*page_fault)(struct kvm_vcpu *vcpu, gva_t gva, u32 err);
> + int (*page_fault)(struct kvm_vcpu *vcpu, gva_t gva, u32 err, bool no_apf);
> void (*inject_page_fault)(struct kvm_vcpu *vcpu);
> void (*free)(struct kvm_vcpu *vcpu);
> gpa_t (*gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t gva, u32 access,
> @@ -838,6 +838,8 @@ void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
> struct kvm_async_pf *work);
> void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
> struct kvm_async_pf *work);
> +void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu,
> + struct kvm_async_pf *work);
> extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
>
> #endif /* _ASM_X86_KVM_HOST_H */
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 4d49b5e..d85fda8 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2558,7 +2558,7 @@ static gpa_t nonpaging_gva_to_gpa_nested(struct kvm_vcpu *vcpu, gva_t vaddr,
> }
>
> static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
> - u32 error_code)
> + u32 error_code, bool no_apf)
> {
> gfn_t gfn;
> int r;
> @@ -2594,8 +2594,8 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu)
> return kvm_x86_ops->interrupt_allowed(vcpu);
> }
>
> -static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
> - pfn_t *pfn)
> +static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn,
> + gva_t gva, pfn_t *pfn)
> {
> bool async;
>
> @@ -2606,7 +2606,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
>
> put_page(pfn_to_page(*pfn));
>
> - if (can_do_async_pf(vcpu)) {
> + if (!no_apf && can_do_async_pf(vcpu)) {
> trace_kvm_try_async_get_page(async, *pfn);
> if (kvm_find_async_pf_gfn(vcpu, gfn)) {
> vcpu->async_pf.work = kvm_double_apf;
> @@ -2620,8 +2620,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
> return false;
> }
>
> -static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
> - u32 error_code)
> +static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
> + bool no_apf)
> {
> pfn_t pfn;
> int r;
> @@ -2643,7 +2643,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
> mmu_seq = vcpu->kvm->mmu_notifier_seq;
> smp_rmb();
>
> - if (try_async_pf(vcpu, gfn, gpa, &pfn))
> + if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn))
> return 0;
>
> /* mmio */
> @@ -3306,7 +3306,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)
> int r;
> enum emulation_result er;
>
> - r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code);
> + r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);
> if (r < 0)
> goto out;
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 8154353..9ad90f8 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -530,8 +530,8 @@ out_gpte_changed:
> * 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,
> - u32 error_code)
> +static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
> + bool no_apf)
> {
> int write_fault = error_code & PFERR_WRITE_MASK;
> int user_fault = error_code & PFERR_USER_MASK;
> @@ -574,7 +574,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
> mmu_seq = vcpu->kvm->mmu_notifier_seq;
> smp_rmb();
>
> - if (try_async_pf(vcpu, walker.gfn, addr, &pfn))
> + if (try_async_pf(vcpu, no_apf, walker.gfn, addr, &pfn))
> return 0;
>
> /* mmio */
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8dd9ac2..48fd59d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6123,6 +6123,13 @@ void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
> }
> EXPORT_SYMBOL_GPL(kvm_set_rflags);
>
> +void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> +{
> + if (!tdp_enabled || is_error_page(work->page))
> + return;
> + vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
> +}
> +
Can't you set a bit in vcpu->requests instead, and handle it in "out:"
at the end of vcpu_enter_guest?
To have a single entry point for pagefaults, after vmexit handling.
--
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