Enabling Access bit when doing memory swapping.
Signed-off-by: Haitao Shan <[email protected]>
Signed-off-by: Xudong Hao <[email protected]>
---
arch/x86/kvm/mmu.c | 13 +++++++------
arch/x86/kvm/vmx.c | 6 ++++--
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ff053ca..5f55f98 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
int young = 0;
/*
- * Emulate the accessed bit for EPT, by checking if this page has
+ * In case of absence of EPT Access and Dirty Bits supports,
+ * emulate the accessed bit for EPT, by checking if this page has
* an EPT mapping, and clearing it if it does. On the next access,
* a new EPT mapping will be established.
* This has some overhead, but not as much as the cost of swapping
@@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
while (spte) {
int _young;
u64 _spte = *spte;
- BUG_ON(!(_spte & PT_PRESENT_MASK));
- _young = _spte & PT_ACCESSED_MASK;
+ BUG_ON(!is_shadow_present_pte(_spte));
+ _young = _spte & shadow_accessed_mask;
if (_young) {
young = 1;
- clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
+ *spte &= ~shadow_accessed_mask;
}
spte = rmap_next(rmapp, spte);
}
@@ -1207,8 +1208,8 @@ static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
spte = rmap_next(rmapp, NULL);
while (spte) {
u64 _spte = *spte;
- BUG_ON(!(_spte & PT_PRESENT_MASK));
- young = _spte & PT_ACCESSED_MASK;
+ BUG_ON(!is_shadow_present_pte(_spte));
+ young = _spte & shadow_accessed_mask;
if (young) {
young = 1;
break;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 89151a9..a3ef549 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7242,8 +7242,10 @@ static int __init vmx_init(void)
vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
if (enable_ept) {
- kvm_mmu_set_mask_ptes(0ull, 0ull, 0ull, 0ull,
- VMX_EPT_EXECUTABLE_MASK);
+ kvm_mmu_set_mask_ptes(0ull,
+ (enable_ept_ad_bits) ? VMX_EPT_ACCESS_BIT : 0ull,
+ (enable_ept_ad_bits) ? VMX_EPT_DIRTY_BIT : 0ull,
+ 0ull, VMX_EPT_EXECUTABLE_MASK);
ept_set_mmio_spte_mask();
kvm_enable_tdp();
} else
--
1.7.1
On Wed, May 16, 2012 at 09:12:30AM +0800, Xudong Hao wrote:
> Enabling Access bit when doing memory swapping.
>
> Signed-off-by: Haitao Shan <[email protected]>
> Signed-off-by: Xudong Hao <[email protected]>
> ---
> arch/x86/kvm/mmu.c | 13 +++++++------
> arch/x86/kvm/vmx.c | 6 ++++--
> 2 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ff053ca..5f55f98 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> int young = 0;
>
> /*
> - * Emulate the accessed bit for EPT, by checking if this page has
> + * In case of absence of EPT Access and Dirty Bits supports,
> + * emulate the accessed bit for EPT, by checking if this page has
> * an EPT mapping, and clearing it if it does. On the next access,
> * a new EPT mapping will be established.
> * This has some overhead, but not as much as the cost of swapping
> @@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> while (spte) {
> int _young;
> u64 _spte = *spte;
> - BUG_ON(!(_spte & PT_PRESENT_MASK));
> - _young = _spte & PT_ACCESSED_MASK;
> + BUG_ON(!is_shadow_present_pte(_spte));
> + _young = _spte & shadow_accessed_mask;
> if (_young) {
> young = 1;
> - clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
> + *spte &= ~shadow_accessed_mask;
> }
Now a dirty bit can be lost. Is there a reason to remove the clear_bit?
> -----Original Message-----
> From: Marcelo Tosatti [mailto:[email protected]]
> Sent: Friday, May 18, 2012 10:23 AM
> To: Xudong Hao
> Cc: [email protected]; [email protected]; [email protected];
> Shan, Haitao; Zhang, Xiantao; Hao, Xudong
> Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
>
> On Wed, May 16, 2012 at 09:12:30AM +0800, Xudong Hao wrote:
> > Enabling Access bit when doing memory swapping.
> >
> > Signed-off-by: Haitao Shan <[email protected]>
> > Signed-off-by: Xudong Hao <[email protected]>
> > ---
> > arch/x86/kvm/mmu.c | 13 +++++++------
> > arch/x86/kvm/vmx.c | 6 ++++--
> > 2 files changed, 11 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index ff053ca..5f55f98 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm,
> unsigned long *rmapp,
> > int young = 0;
> >
> > /*
> > - * Emulate the accessed bit for EPT, by checking if this page has
> > + * In case of absence of EPT Access and Dirty Bits supports,
> > + * emulate the accessed bit for EPT, by checking if this page has
> > * an EPT mapping, and clearing it if it does. On the next access,
> > * a new EPT mapping will be established.
> > * This has some overhead, but not as much as the cost of swapping
> > @@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm,
> unsigned long *rmapp,
> > while (spte) {
> > int _young;
> > u64 _spte = *spte;
> > - BUG_ON(!(_spte & PT_PRESENT_MASK));
> > - _young = _spte & PT_ACCESSED_MASK;
> > + BUG_ON(!is_shadow_present_pte(_spte));
> > + _young = _spte & shadow_accessed_mask;
> > if (_young) {
> > young = 1;
> > - clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
> > + *spte &= ~shadow_accessed_mask;
> > }
>
> Now a dirty bit can be lost. Is there a reason to remove the clear_bit?
The clear_bit() is called in shadown and EPT A/D mode, because PT_ACCESSED_SHIFT does not make sense for EPT A/D bit, so use the code shadow_accessed_mask to mask the bit for both of them.
On 05/21/2012 06:22 AM, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Marcelo Tosatti [mailto:[email protected]]
> > Sent: Friday, May 18, 2012 10:23 AM
> > To: Xudong Hao
> > Cc: [email protected]; [email protected]; [email protected];
> > Shan, Haitao; Zhang, Xiantao; Hao, Xudong
> > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
> >
> > On Wed, May 16, 2012 at 09:12:30AM +0800, Xudong Hao wrote:
> > > Enabling Access bit when doing memory swapping.
> > >
> > > Signed-off-by: Haitao Shan <[email protected]>
> > > Signed-off-by: Xudong Hao <[email protected]>
> > > ---
> > > arch/x86/kvm/mmu.c | 13 +++++++------
> > > arch/x86/kvm/vmx.c | 6 ++++--
> > > 2 files changed, 11 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > > index ff053ca..5f55f98 100644
> > > --- a/arch/x86/kvm/mmu.c
> > > +++ b/arch/x86/kvm/mmu.c
> > > @@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm,
> > unsigned long *rmapp,
> > > int young = 0;
> > >
> > > /*
> > > - * Emulate the accessed bit for EPT, by checking if this page has
> > > + * In case of absence of EPT Access and Dirty Bits supports,
> > > + * emulate the accessed bit for EPT, by checking if this page has
> > > * an EPT mapping, and clearing it if it does. On the next access,
> > > * a new EPT mapping will be established.
> > > * This has some overhead, but not as much as the cost of swapping
> > > @@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm,
> > unsigned long *rmapp,
> > > while (spte) {
> > > int _young;
> > > u64 _spte = *spte;
> > > - BUG_ON(!(_spte & PT_PRESENT_MASK));
> > > - _young = _spte & PT_ACCESSED_MASK;
> > > + BUG_ON(!is_shadow_present_pte(_spte));
> > > + _young = _spte & shadow_accessed_mask;
> > > if (_young) {
> > > young = 1;
> > > - clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
> > > + *spte &= ~shadow_accessed_mask;
> > > }
> >
> > Now a dirty bit can be lost. Is there a reason to remove the clear_bit?
>
> The clear_bit() is called in shadown and EPT A/D mode, because PT_ACCESSED_SHIFT does not make sense for EPT A/D bit, so use the code shadow_accessed_mask to mask the bit for both of them.
That doesn't answer the question. An atomic operation is now non-atomic.
You can calculate shadow_accessed_bit and keep on using clear_bit(), or
switch to cmpxchg64(), but don't just drop the dirty bit here.
--
error compiling committee.c: too many arguments to function
> -----Original Message-----
> From: Avi Kivity [mailto:[email protected]]
> Sent: Monday, May 21, 2012 4:32 PM
> To: Hao, Xudong
> Cc: Marcelo Tosatti; Xudong Hao; [email protected];
> [email protected]; Shan, Haitao; Zhang, Xiantao
> Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
>
> On 05/21/2012 06:22 AM, Hao, Xudong wrote:
> > > -----Original Message-----
> > > From: Marcelo Tosatti [mailto:[email protected]]
> > > Sent: Friday, May 18, 2012 10:23 AM
> > > To: Xudong Hao
> > > Cc: [email protected]; [email protected]; [email protected];
> > > Shan, Haitao; Zhang, Xiantao; Hao, Xudong
> > > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
> > >
> > > On Wed, May 16, 2012 at 09:12:30AM +0800, Xudong Hao wrote:
> > > > Enabling Access bit when doing memory swapping.
> > > >
> > > > Signed-off-by: Haitao Shan <[email protected]>
> > > > Signed-off-by: Xudong Hao <[email protected]>
> > > > ---
> > > > arch/x86/kvm/mmu.c | 13 +++++++------
> > > > arch/x86/kvm/vmx.c | 6 ++++--
> > > > 2 files changed, 11 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > > > index ff053ca..5f55f98 100644
> > > > --- a/arch/x86/kvm/mmu.c
> > > > +++ b/arch/x86/kvm/mmu.c
> > > > @@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm,
> > > unsigned long *rmapp,
> > > > int young = 0;
> > > >
> > > > /*
> > > > - * Emulate the accessed bit for EPT, by checking if this page has
> > > > + * In case of absence of EPT Access and Dirty Bits supports,
> > > > + * emulate the accessed bit for EPT, by checking if this page has
> > > > * an EPT mapping, and clearing it if it does. On the next access,
> > > > * a new EPT mapping will be established.
> > > > * This has some overhead, but not as much as the cost of swapping
> > > > @@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm,
> > > unsigned long *rmapp,
> > > > while (spte) {
> > > > int _young;
> > > > u64 _spte = *spte;
> > > > - BUG_ON(!(_spte & PT_PRESENT_MASK));
> > > > - _young = _spte & PT_ACCESSED_MASK;
> > > > + BUG_ON(!is_shadow_present_pte(_spte));
> > > > + _young = _spte & shadow_accessed_mask;
> > > > if (_young) {
> > > > young = 1;
> > > > - clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
> > > > + *spte &= ~shadow_accessed_mask;
> > > > }
> > >
> > > Now a dirty bit can be lost. Is there a reason to remove the clear_bit?
> >
> > The clear_bit() is called in shadown and EPT A/D mode, because
> PT_ACCESSED_SHIFT does not make sense for EPT A/D bit, so use the code
> shadow_accessed_mask to mask the bit for both of them.
>
> That doesn't answer the question. An atomic operation is now non-atomic.
>
> You can calculate shadow_accessed_bit and keep on using clear_bit(), or
> switch to cmpxchg64(), but don't just drop the dirty bit here.
>
I know your meaning. How about this changes:
...
young = 1;
+ if (enable_ept_ad_bits)
+ clear_bit(ffs(shadow_accessed_mask), (unsigned long *)spte);
clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
...
> --
> error compiling committee.c: too many arguments to function
On 05/21/2012 01:35 PM, Hao, Xudong wrote:
> >
> > That doesn't answer the question. An atomic operation is now non-atomic.
> >
> > You can calculate shadow_accessed_bit and keep on using clear_bit(), or
> > switch to cmpxchg64(), but don't just drop the dirty bit here.
> >
>
> I know your meaning. How about this changes:
>
> ...
> young = 1;
> + if (enable_ept_ad_bits)
> + clear_bit(ffs(shadow_accessed_mask), (unsigned long *)spte);
ffs() returns an off-by-one result, so this needs to be adjusted. IIRC
bsfl is slow, but this shouldn't be a problem here.
--
error compiling committee.c: too many arguments to function
> -----Original Message-----
> From: Avi Kivity [mailto:[email protected]]
> Sent: Monday, May 21, 2012 6:48 PM
> To: Hao, Xudong
> Cc: Marcelo Tosatti; Xudong Hao; [email protected];
> [email protected]; Shan, Haitao; Zhang, Xiantao
> Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
>
> On 05/21/2012 01:35 PM, Hao, Xudong wrote:
> > >
> > > That doesn't answer the question. An atomic operation is now
> non-atomic.
> > >
> > > You can calculate shadow_accessed_bit and keep on using clear_bit(), or
> > > switch to cmpxchg64(), but don't just drop the dirty bit here.
> > >
> >
> > I know your meaning. How about this changes:
> >
> > ...
> > young = 1;
> > + if (enable_ept_ad_bits)
> > + clear_bit(ffs(shadow_accessed_mask), (unsigned long
> *)spte);
>
> ffs() returns an off-by-one result, so this needs to be adjusted.
Yes, it need to decrease 1, I'll send v3 version for patch4, any other comments?
> IIRC
> bsfl is slow, but this shouldn't be a problem here.
>
I do not know the story...
>
> --
> error compiling committee.c: too many arguments to function
On 05/21/2012 02:17 PM, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Avi Kivity [mailto:[email protected]]
> > Sent: Monday, May 21, 2012 6:48 PM
> > To: Hao, Xudong
> > Cc: Marcelo Tosatti; Xudong Hao; [email protected];
> > [email protected]; Shan, Haitao; Zhang, Xiantao
> > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
> >
> > On 05/21/2012 01:35 PM, Hao, Xudong wrote:
> > > >
> > > > That doesn't answer the question. An atomic operation is now
> > non-atomic.
> > > >
> > > > You can calculate shadow_accessed_bit and keep on using clear_bit(), or
> > > > switch to cmpxchg64(), but don't just drop the dirty bit here.
> > > >
> > >
> > > I know your meaning. How about this changes:
> > >
> > > ...
> > > young = 1;
> > > + if (enable_ept_ad_bits)
> > > + clear_bit(ffs(shadow_accessed_mask), (unsigned long
> > *)spte);
> >
> > ffs() returns an off-by-one result, so this needs to be adjusted.
>
> Yes, it need to decrease 1, I'll send v3 version for patch4, any other comments?
I think it's fine.
> > IIRC
> > bsfl is slow, but this shouldn't be a problem here.
> >
>
> I do not know the story...
>
No story, bsf is a relatively slow instruction, but it shouldn't affect
us here; this isn't a fast path and in any case it's only a few cycles.
--
error compiling committee.c: too many arguments to function