diff mbox series

[v12,08/20] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA

Message ID 20240115125707.1183-9-paul@xen.org (mailing list archive)
State New, archived
Headers show
Series KVM: xen: update shared_info and vcpu_info handling | expand

Commit Message

Paul Durrant Jan. 15, 2024, 12:56 p.m. UTC 
From: Paul Durrant <pdurrant@amazon.com>

Some pfncache pages may actually be overlays on guest memory that have a
fixed HVA within the VMM. It's pointless to invalidate such cached
mappings if the overlay is moved so allow a cache to be activated directly
with the HVA to cater for such cases. A subsequent patch will make use
of this facility.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>

v11:
 - Fixed kvm_gpc_check() to ignore memslot generation if the cache is not
   activated with a GPA. (This breakage occured during the re-work for v8).

v9:
 - Pass both GPA and HVA into __kvm_gpc_refresh() rather than overloading
   the address paraneter and using a bool flag to indicated what it is.

v8:
 - Re-worked to avoid messing with struct gfn_to_pfn_cache.
---
 include/linux/kvm_host.h | 20 +++++++++++++++++++-
 virt/kvm/pfncache.c      | 40 +++++++++++++++++++++++++++++++---------
 2 files changed, 50 insertions(+), 10 deletions(-)

Comments

Sean Christopherson Feb. 7, 2024, 4:03 a.m. UTC | #1 
+s390 folks (question on kvm_is_error_gpa() for ya)

On Mon, Jan 15, 2024, Paul Durrant wrote:
> @@ -1398,7 +1414,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>  static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
>  {
>  	lockdep_assert_held(&gpc->lock);
> -	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
> +
> +	if (gpc->gpa != KVM_XEN_INVALID_GPA)

KVM_XEN_INVALID_GPA absolutely doesn't belong in common code.  Not to mention
that it will break when Paolo (rightly) moves it to an x86 header.

https://lore.kernel.org/all/20240131233056.10845-3-pbonzini@redhat.com

> +		mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
>  }
>  
>  void kvm_sigset_activate(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
> index 97eec8ee3449..ae822bff812f 100644
> --- a/virt/kvm/pfncache.c
> +++ b/virt/kvm/pfncache.c
> @@ -48,7 +48,10 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
>  	if (!gpc->active)
>  		return false;
>  
> -	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
> +	if (gpc->gpa != KVM_XEN_INVALID_GPA && gpc->generation != slots->generation)

This needs a comment.  I know what it's doing, but it wasn't obvious at first
glance, and it definitely won't be intuitive for readers that aren't intimately
familiar with memslots.

> +		return false;
> +
> +	if (kvm_is_error_hva(gpc->uhva))
>  		return false;
>  
>  	if (offset_in_page(gpc->uhva) + len > PAGE_SIZE)
> @@ -209,11 +212,13 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
>  	return -EFAULT;
>  }
>  
> -static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
> +static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,
>  			     unsigned long len)
>  {
>  	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
> -	unsigned long page_offset = offset_in_page(gpa);
> +	unsigned long page_offset = (gpa != KVM_XEN_INVALID_GPA) ?
> +		offset_in_page(gpa) :
> +		offset_in_page(uhva);

This formatting is funky.  I also think it would be worth adding a helper to pair
with kvm_is_error_hva().

But!  kvm_is_error_gpa() already exists, and it very, very sneakily does a memslot
lookup and checks for a valid HVA.

s390 people, any objection to renaming kvm_is_error_gpa() to something like
kvm_gpa_has_memslot() or kvm_gpa_is_in_memslot()?  s390 is the only code that
uses the existing helper.

That would both to free up the name to pair with kvm_is_error_hva(), and would
make it obvious what the helper does; I was quite surprised that "error" means
"is covered by a valid memslot".

Back to this code, then we can have a slightly cleaner:

	unsigned long page_offset = kvm_is_error_gpa(gpa) ? offset_in_page(gpa) :
							    offset_in_page(uhva);


And I think it's worth asserting that exactly _one_ of GPA or HVA is valid, e.g.
to ensure KVM doesn't end up with botched offsets, and to make it a bit more
clear what's going on.


	if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva))
		return -EINVAL;
David Woodhouse Feb. 7, 2024, 4:13 a.m. UTC | #2 
On Tue, 2024-02-06 at 20:03 -0800, Sean Christopherson wrote:
> +s390 folks (question on kvm_is_error_gpa() for ya)
> 
> On Mon, Jan 15, 2024, Paul Durrant wrote:
> > @@ -1398,7 +1414,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
> >   static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
> >   {
> >         lockdep_assert_held(&gpc->lock);
> > -       mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
> > +
> > +       if (gpc->gpa != KVM_XEN_INVALID_GPA)
> 
> KVM_XEN_INVALID_GPA absolutely doesn't belong in common code.  Not to mention
> that it will break when Paolo (rightly) moves it to an x86 header.
> 
> https://lore.kernel.org/all/20240131233056.10845-3-pbonzini@redhat.com

We can use plain INVALID_GPA for that, I think. ISTR the reason we have
a separate KVM_XEN_INVALID_GPA is because that's a userspace API.

...

> But!  kvm_is_error_gpa() already exists, and it very, very sneakily
> does a memslot lookup and checks for a valid HVA.

Hm, that doesn't sound as fast as simple comparison. We also can't do
it from kvm_gpc_check(), can we?
Paul Durrant Feb. 14, 2024, 3:21 p.m. UTC | #3 
On 07/02/2024 04:03, Sean Christopherson wrote:
> +s390 folks (question on kvm_is_error_gpa() for ya)
> 
> On Mon, Jan 15, 2024, Paul Durrant wrote:
>> @@ -1398,7 +1414,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>>   static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
>>   {
>>   	lockdep_assert_held(&gpc->lock);
>> -	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
>> +
>> +	if (gpc->gpa != KVM_XEN_INVALID_GPA)
> 
> KVM_XEN_INVALID_GPA absolutely doesn't belong in common code.  Not to mention
> that it will break when Paolo (rightly) moves it to an x86 header.
> 
> https://lore.kernel.org/all/20240131233056.10845-3-pbonzini@redhat.com
> 
>> +		mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
>>   }
>>   
>>   void kvm_sigset_activate(struct kvm_vcpu *vcpu);
>> diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
>> index 97eec8ee3449..ae822bff812f 100644
>> --- a/virt/kvm/pfncache.c
>> +++ b/virt/kvm/pfncache.c
>> @@ -48,7 +48,10 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
>>   	if (!gpc->active)
>>   		return false;
>>   
>> -	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
>> +	if (gpc->gpa != KVM_XEN_INVALID_GPA && gpc->generation != slots->generation)
> 
> This needs a comment.  I know what it's doing, but it wasn't obvious at first
> glance, and it definitely won't be intuitive for readers that aren't intimately
> familiar with memslots.
> 
>> +		return false;
>> +
>> +	if (kvm_is_error_hva(gpc->uhva))
>>   		return false;
>>   
>>   	if (offset_in_page(gpc->uhva) + len > PAGE_SIZE)
>> @@ -209,11 +212,13 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
>>   	return -EFAULT;
>>   }
>>   
>> -static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
>> +static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,
>>   			     unsigned long len)
>>   {
>>   	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
>> -	unsigned long page_offset = offset_in_page(gpa);
>> +	unsigned long page_offset = (gpa != KVM_XEN_INVALID_GPA) ?
>> +		offset_in_page(gpa) :
>> +		offset_in_page(uhva);
> 
> This formatting is funky.  I also think it would be worth adding a helper to pair
> with kvm_is_error_hva().
> 
> But!  kvm_is_error_gpa() already exists, and it very, very sneakily does a memslot
> lookup and checks for a valid HVA.
> 
> s390 people, any objection to renaming kvm_is_error_gpa() to something like
> kvm_gpa_has_memslot() or kvm_gpa_is_in_memslot()?  s390 is the only code that
> uses the existing helper.
> 
> That would both to free up the name to pair with kvm_is_error_hva(), and would
> make it obvious what the helper does; I was quite surprised that "error" means
> "is covered by a valid memslot".
> 

Seemingly no response to this; I'll define a local helper rather than 
re-working the open-coded tests to check against INVALID_GPA. This can 
then be trivially replaced if need be.

> Back to this code, then we can have a slightly cleaner:
> 
> 	unsigned long page_offset = kvm_is_error_gpa(gpa) ? offset_in_page(gpa) :
> 							    offset_in_page(uhva);
> 
> 
> And I think it's worth asserting that exactly _one_ of GPA or HVA is valid, e.g.
> to ensure KVM doesn't end up with botched offsets, and to make it a bit more
> clear what's going on.
> 
> 
> 	if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva))
> 		return -EINVAL;

Sure.
Sean Christopherson Feb. 14, 2024, 4:01 p.m. UTC | #4 
On Tue, Feb 06, 2024, David Woodhouse wrote:
> On Tue, 2024-02-06 at 20:03 -0800, Sean Christopherson wrote:
> > +s390 folks (question on kvm_is_error_gpa() for ya)
> > 
> > On Mon, Jan 15, 2024, Paul Durrant wrote:
> > > @@ -1398,7 +1414,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
> > >   static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
> > >   {
> > >         lockdep_assert_held(&gpc->lock);
> > > -       mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
> > > +
> > > +       if (gpc->gpa != KVM_XEN_INVALID_GPA)
> > 
> > KVM_XEN_INVALID_GPA absolutely doesn't belong in common code.  Not to mention
> > that it will break when Paolo (rightly) moves it to an x86 header.
> > 
> > https://lore.kernel.org/all/20240131233056.10845-3-pbonzini@redhat.com
> 
> We can use plain INVALID_GPA for that, I think. ISTR the reason we have
> a separate KVM_XEN_INVALID_GPA is because that's a userspace API.
> 
> ...
> 
> > But!  kvm_is_error_gpa() already exists, and it very, very sneakily
> > does a memslot lookup and checks for a valid HVA.
> 
> Hm, that doesn't sound as fast as simple comparison. We also can't do
> it from kvm_gpc_check(), can we?

You snipped the part where I suggested renaming the existing kvm_is_error_gpa().

I am suggesting we do the below (and obviously rename the s390 usage, too), and
then the gpc code can use use kvm_is_error_gpa().

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bbfefd7e612f..e1df988e4d57 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -148,6 +148,11 @@ static inline bool kvm_is_error_hva(unsigned long addr)
 
 #endif
 
+static inline bool kvm_is_error_gpa(gpa_t gpa)
+{
+       return gpa == INVALID_GPA;
+}
+
 #define KVM_ERR_PTR_BAD_PAGE   (ERR_PTR(-ENOENT))
 
 static inline bool is_error_page(struct page *page)
@@ -1787,7 +1792,7 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
        return (hpa_t)pfn << PAGE_SHIFT;
 }
 
-static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
+static inline bool kvm_gpa_is_in_memslot(struct kvm *kvm, gpa_t gpa)
 {
        unsigned long hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));
Paul Durrant Feb. 14, 2024, 4:09 p.m. UTC | #5 
On 14/02/2024 16:01, Sean Christopherson wrote:
> On Tue, Feb 06, 2024, David Woodhouse wrote:
>> On Tue, 2024-02-06 at 20:03 -0800, Sean Christopherson wrote:
>>> +s390 folks (question on kvm_is_error_gpa() for ya)
>>>
>>> On Mon, Jan 15, 2024, Paul Durrant wrote:
>>>> @@ -1398,7 +1414,9 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>>>>    static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
>>>>    {
>>>>          lockdep_assert_held(&gpc->lock);
>>>> -       mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
>>>> +
>>>> +       if (gpc->gpa != KVM_XEN_INVALID_GPA)
>>>
>>> KVM_XEN_INVALID_GPA absolutely doesn't belong in common code.  Not to mention
>>> that it will break when Paolo (rightly) moves it to an x86 header.
>>>
>>> https://lore.kernel.org/all/20240131233056.10845-3-pbonzini@redhat.com
>>
>> We can use plain INVALID_GPA for that, I think. ISTR the reason we have
>> a separate KVM_XEN_INVALID_GPA is because that's a userspace API.
>>
>> ...
>>
>>> But!  kvm_is_error_gpa() already exists, and it very, very sneakily
>>> does a memslot lookup and checks for a valid HVA.
>>
>> Hm, that doesn't sound as fast as simple comparison. We also can't do
>> it from kvm_gpc_check(), can we?
> 
> You snipped the part where I suggested renaming the existing kvm_is_error_gpa().
> 
> I am suggesting we do the below (and obviously rename the s390 usage, too), and
> then the gpc code can use use kvm_is_error_gpa().
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index bbfefd7e612f..e1df988e4d57 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -148,6 +148,11 @@ static inline bool kvm_is_error_hva(unsigned long addr)
>   
>   #endif
>   
> +static inline bool kvm_is_error_gpa(gpa_t gpa)
> +{
> +       return gpa == INVALID_GPA;
> +}
> +

Are you ok with a local kvm_gpc_is_error_gpa() or somesuch until there 
is agreement with s390?

   Paul

>   #define KVM_ERR_PTR_BAD_PAGE   (ERR_PTR(-ENOENT))
>   
>   static inline bool is_error_page(struct page *page)
> @@ -1787,7 +1792,7 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
>          return (hpa_t)pfn << PAGE_SHIFT;
>   }
>   
> -static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
> +static inline bool kvm_gpa_is_in_memslot(struct kvm *kvm, gpa_t gpa)
>   {
>          unsigned long hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));
>
Sean Christopherson Feb. 14, 2024, 4:20 p.m. UTC | #6 
On Wed, Feb 14, 2024, Paul Durrant wrote:
> On 07/02/2024 04:03, Sean Christopherson wrote:
> > +s390 folks (question on kvm_is_error_gpa() for ya)
> > But!  kvm_is_error_gpa() already exists, and it very, very sneakily does a memslot
> > lookup and checks for a valid HVA.
> > 
> > s390 people, any objection to renaming kvm_is_error_gpa() to something like
> > kvm_gpa_has_memslot() or kvm_gpa_is_in_memslot()?  s390 is the only code that
> > uses the existing helper.
> > 
> > That would both to free up the name to pair with kvm_is_error_hva(), and would
> > make it obvious what the helper does; I was quite surprised that "error" means
> > "is covered by a valid memslot".
> > 
> 
> Seemingly no response to this; I'll define a local helper rather than
> re-working the open-coded tests to check against INVALID_GPA. This can then
> be trivially replaced if need be.

How about we force a decision with a patch?  This should be easy enough to slot
in, and I would be quite surprised if s390 is overly attached to kvm_is_error_gpa().

From: Sean Christopherson <seanjc@google.com>
Date: Wed, 14 Feb 2024 08:05:49 -0800
Subject: [PATCH] KVM: s390: Refactor kvm_is_error_gpa() into
 kvm_is_gpa_in_memslot()

Rename kvm_is_error_gpa() to kvm_is_gpa_in_memslot() and invert the
polarity accordingly in order to (a) free up kvm_is_error_gpa() to match
with kvm_is_error_{hva,page}(), and (b) to make it more obvious that the
helper is doing a memslot lookup, i.e. not simply checking for INVALID_GPA.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/s390/kvm/diag.c     |  2 +-
 arch/s390/kvm/gaccess.c  | 14 +++++++-------
 arch/s390/kvm/kvm-s390.c |  4 ++--
 arch/s390/kvm/priv.c     |  4 ++--
 arch/s390/kvm/sigp.c     |  2 +-
 include/linux/kvm_host.h |  4 ++--
 6 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 3c65b8258ae6..2a32438e09ce 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -102,7 +102,7 @@ static int __diag_page_ref_service(struct kvm_vcpu *vcpu)
 		    parm.token_addr & 7 || parm.zarch != 0x8000000000000000ULL)
 			return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
 
-		if (kvm_is_error_gpa(vcpu->kvm, parm.token_addr))
+		if (!kvm_is_gpa_in_memslot(vcpu->kvm, parm.token_addr))
 			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
 
 		vcpu->arch.pfault_token = parm.token_addr;
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 5bfcc50c1a68..415c99649e43 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -664,7 +664,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 	case ASCE_TYPE_REGION1:	{
 		union region1_table_entry rfte;
 
-		if (kvm_is_error_gpa(vcpu->kvm, ptr))
+		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
 			return PGM_ADDRESSING;
 		if (deref_table(vcpu->kvm, ptr, &rfte.val))
 			return -EFAULT;
@@ -682,7 +682,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 	case ASCE_TYPE_REGION2: {
 		union region2_table_entry rste;
 
-		if (kvm_is_error_gpa(vcpu->kvm, ptr))
+		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
 			return PGM_ADDRESSING;
 		if (deref_table(vcpu->kvm, ptr, &rste.val))
 			return -EFAULT;
@@ -700,7 +700,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 	case ASCE_TYPE_REGION3: {
 		union region3_table_entry rtte;
 
-		if (kvm_is_error_gpa(vcpu->kvm, ptr))
+		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
 			return PGM_ADDRESSING;
 		if (deref_table(vcpu->kvm, ptr, &rtte.val))
 			return -EFAULT;
@@ -728,7 +728,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 	case ASCE_TYPE_SEGMENT: {
 		union segment_table_entry ste;
 
-		if (kvm_is_error_gpa(vcpu->kvm, ptr))
+		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
 			return PGM_ADDRESSING;
 		if (deref_table(vcpu->kvm, ptr, &ste.val))
 			return -EFAULT;
@@ -748,7 +748,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 		ptr = ste.fc0.pto * (PAGE_SIZE / 2) + vaddr.px * 8;
 	}
 	}
-	if (kvm_is_error_gpa(vcpu->kvm, ptr))
+	if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
 		return PGM_ADDRESSING;
 	if (deref_table(vcpu->kvm, ptr, &pte.val))
 		return -EFAULT;
@@ -770,7 +770,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
 		*prot = PROT_TYPE_IEP;
 		return PGM_PROTECTION;
 	}
-	if (kvm_is_error_gpa(vcpu->kvm, raddr.addr))
+	if (!kvm_is_gpa_in_memslot(vcpu->kvm, raddr.addr))
 		return PGM_ADDRESSING;
 	*gpa = raddr.addr;
 	return 0;
@@ -957,7 +957,7 @@ static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 				return rc;
 		} else {
 			gpa = kvm_s390_real_to_abs(vcpu, ga);
-			if (kvm_is_error_gpa(vcpu->kvm, gpa)) {
+			if (!kvm_is_gpa_in_memslot(vcpu->kvm, gpa)) {
 				rc = PGM_ADDRESSING;
 				prot = PROT_NONE;
 			}
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ea63ac769889..3e5a1d7aa81a 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2878,7 +2878,7 @@ static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
 
 	srcu_idx = srcu_read_lock(&kvm->srcu);
 
-	if (kvm_is_error_gpa(kvm, mop->gaddr)) {
+	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
 		r = PGM_ADDRESSING;
 		goto out_unlock;
 	}
@@ -2940,7 +2940,7 @@ static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *m
 
 	srcu_idx = srcu_read_lock(&kvm->srcu);
 
-	if (kvm_is_error_gpa(kvm, mop->gaddr)) {
+	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
 		r = PGM_ADDRESSING;
 		goto out_unlock;
 	}
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index f875a404a0a0..1be19cc9d73c 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -149,7 +149,7 @@ static int handle_set_prefix(struct kvm_vcpu *vcpu)
 	 * first page, since address is 8k aligned and memory pieces are always
 	 * at least 1MB aligned and have at least a size of 1MB.
 	 */
-	if (kvm_is_error_gpa(vcpu->kvm, address))
+	if (!kvm_is_gpa_in_memslot(vcpu->kvm, address))
 		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
 
 	kvm_s390_set_prefix(vcpu, address);
@@ -464,7 +464,7 @@ static int handle_test_block(struct kvm_vcpu *vcpu)
 		return kvm_s390_inject_prog_irq(vcpu, &vcpu->arch.pgm);
 	addr = kvm_s390_real_to_abs(vcpu, addr);
 
-	if (kvm_is_error_gpa(vcpu->kvm, addr))
+	if (!kvm_is_gpa_in_memslot(vcpu->kvm, addr))
 		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
 	/*
 	 * We don't expect errors on modern systems, and do not care
diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index d9696b530064..55c34cb35428 100644
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -172,7 +172,7 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, struct kvm_vcpu *dst_vcpu,
 	 * first page, since address is 8k aligned and memory pieces are always
 	 * at least 1MB aligned and have at least a size of 1MB.
 	 */
-	if (kvm_is_error_gpa(vcpu->kvm, irq.u.prefix.address)) {
+	if (!kvm_is_gpa_in_memslot(vcpu->kvm, irq.u.prefix.address)) {
 		*reg &= 0xffffffff00000000UL;
 		*reg |= SIGP_STATUS_INVALID_PARAMETER;
 		return SIGP_CC_STATUS_STORED;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7e7fd25b09b3..d175b64488ec 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1788,11 +1788,11 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
 	return (hpa_t)pfn << PAGE_SHIFT;
 }
 
-static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
+static inline bool kvm_is_gpa_in_memslot(struct kvm *kvm, gpa_t gpa)
 {
 	unsigned long hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));
 
-	return kvm_is_error_hva(hva);
+	return !kvm_is_error_hva(hva);
 }
 
 enum kvm_stat_kind {

base-commit: 687d8f4c3dea0758afd748968d91288220bbe7e3
--
Paul Durrant Feb. 14, 2024, 4:33 p.m. UTC | #7 
On 14/02/2024 16:20, Sean Christopherson wrote:
> On Wed, Feb 14, 2024, Paul Durrant wrote:
>> On 07/02/2024 04:03, Sean Christopherson wrote:
>>> +s390 folks (question on kvm_is_error_gpa() for ya)
>>> But!  kvm_is_error_gpa() already exists, and it very, very sneakily does a memslot
>>> lookup and checks for a valid HVA.
>>>
>>> s390 people, any objection to renaming kvm_is_error_gpa() to something like
>>> kvm_gpa_has_memslot() or kvm_gpa_is_in_memslot()?  s390 is the only code that
>>> uses the existing helper.
>>>
>>> That would both to free up the name to pair with kvm_is_error_hva(), and would
>>> make it obvious what the helper does; I was quite surprised that "error" means
>>> "is covered by a valid memslot".
>>>
>>
>> Seemingly no response to this; I'll define a local helper rather than
>> re-working the open-coded tests to check against INVALID_GPA. This can then
>> be trivially replaced if need be.
> 
> How about we force a decision with a patch?  This should be easy enough to slot
> in, and I would be quite surprised if s390 is overly attached to kvm_is_error_gpa().
> 

Ok. I'll slot that in.

> From: Sean Christopherson <seanjc@google.com>
> Date: Wed, 14 Feb 2024 08:05:49 -0800
> Subject: [PATCH] KVM: s390: Refactor kvm_is_error_gpa() into
>   kvm_is_gpa_in_memslot()
> 
> Rename kvm_is_error_gpa() to kvm_is_gpa_in_memslot() and invert the
> polarity accordingly in order to (a) free up kvm_is_error_gpa() to match
> with kvm_is_error_{hva,page}(), and (b) to make it more obvious that the
> helper is doing a memslot lookup, i.e. not simply checking for INVALID_GPA.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   arch/s390/kvm/diag.c     |  2 +-
>   arch/s390/kvm/gaccess.c  | 14 +++++++-------
>   arch/s390/kvm/kvm-s390.c |  4 ++--
>   arch/s390/kvm/priv.c     |  4 ++--
>   arch/s390/kvm/sigp.c     |  2 +-
>   include/linux/kvm_host.h |  4 ++--
>   6 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> index 3c65b8258ae6..2a32438e09ce 100644
> --- a/arch/s390/kvm/diag.c
> +++ b/arch/s390/kvm/diag.c
> @@ -102,7 +102,7 @@ static int __diag_page_ref_service(struct kvm_vcpu *vcpu)
>   		    parm.token_addr & 7 || parm.zarch != 0x8000000000000000ULL)
>   			return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>   
> -		if (kvm_is_error_gpa(vcpu->kvm, parm.token_addr))
> +		if (!kvm_is_gpa_in_memslot(vcpu->kvm, parm.token_addr))
>   			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>   
>   		vcpu->arch.pfault_token = parm.token_addr;
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index 5bfcc50c1a68..415c99649e43 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -664,7 +664,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   	case ASCE_TYPE_REGION1:	{
>   		union region1_table_entry rfte;
>   
> -		if (kvm_is_error_gpa(vcpu->kvm, ptr))
> +		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
>   			return PGM_ADDRESSING;
>   		if (deref_table(vcpu->kvm, ptr, &rfte.val))
>   			return -EFAULT;
> @@ -682,7 +682,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   	case ASCE_TYPE_REGION2: {
>   		union region2_table_entry rste;
>   
> -		if (kvm_is_error_gpa(vcpu->kvm, ptr))
> +		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
>   			return PGM_ADDRESSING;
>   		if (deref_table(vcpu->kvm, ptr, &rste.val))
>   			return -EFAULT;
> @@ -700,7 +700,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   	case ASCE_TYPE_REGION3: {
>   		union region3_table_entry rtte;
>   
> -		if (kvm_is_error_gpa(vcpu->kvm, ptr))
> +		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
>   			return PGM_ADDRESSING;
>   		if (deref_table(vcpu->kvm, ptr, &rtte.val))
>   			return -EFAULT;
> @@ -728,7 +728,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   	case ASCE_TYPE_SEGMENT: {
>   		union segment_table_entry ste;
>   
> -		if (kvm_is_error_gpa(vcpu->kvm, ptr))
> +		if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
>   			return PGM_ADDRESSING;
>   		if (deref_table(vcpu->kvm, ptr, &ste.val))
>   			return -EFAULT;
> @@ -748,7 +748,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   		ptr = ste.fc0.pto * (PAGE_SIZE / 2) + vaddr.px * 8;
>   	}
>   	}
> -	if (kvm_is_error_gpa(vcpu->kvm, ptr))
> +	if (!kvm_is_gpa_in_memslot(vcpu->kvm, ptr))
>   		return PGM_ADDRESSING;
>   	if (deref_table(vcpu->kvm, ptr, &pte.val))
>   		return -EFAULT;
> @@ -770,7 +770,7 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
>   		*prot = PROT_TYPE_IEP;
>   		return PGM_PROTECTION;
>   	}
> -	if (kvm_is_error_gpa(vcpu->kvm, raddr.addr))
> +	if (!kvm_is_gpa_in_memslot(vcpu->kvm, raddr.addr))
>   		return PGM_ADDRESSING;
>   	*gpa = raddr.addr;
>   	return 0;
> @@ -957,7 +957,7 @@ static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
>   				return rc;
>   		} else {
>   			gpa = kvm_s390_real_to_abs(vcpu, ga);
> -			if (kvm_is_error_gpa(vcpu->kvm, gpa)) {
> +			if (!kvm_is_gpa_in_memslot(vcpu->kvm, gpa)) {
>   				rc = PGM_ADDRESSING;
>   				prot = PROT_NONE;
>   			}
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index ea63ac769889..3e5a1d7aa81a 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2878,7 +2878,7 @@ static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
>   
>   	srcu_idx = srcu_read_lock(&kvm->srcu);
>   
> -	if (kvm_is_error_gpa(kvm, mop->gaddr)) {
> +	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
>   		r = PGM_ADDRESSING;
>   		goto out_unlock;
>   	}
> @@ -2940,7 +2940,7 @@ static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *m
>   
>   	srcu_idx = srcu_read_lock(&kvm->srcu);
>   
> -	if (kvm_is_error_gpa(kvm, mop->gaddr)) {
> +	if (!kvm_is_gpa_in_memslot(kvm, mop->gaddr)) {
>   		r = PGM_ADDRESSING;
>   		goto out_unlock;
>   	}
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index f875a404a0a0..1be19cc9d73c 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -149,7 +149,7 @@ static int handle_set_prefix(struct kvm_vcpu *vcpu)
>   	 * first page, since address is 8k aligned and memory pieces are always
>   	 * at least 1MB aligned and have at least a size of 1MB.
>   	 */
> -	if (kvm_is_error_gpa(vcpu->kvm, address))
> +	if (!kvm_is_gpa_in_memslot(vcpu->kvm, address))
>   		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>   
>   	kvm_s390_set_prefix(vcpu, address);
> @@ -464,7 +464,7 @@ static int handle_test_block(struct kvm_vcpu *vcpu)
>   		return kvm_s390_inject_prog_irq(vcpu, &vcpu->arch.pgm);
>   	addr = kvm_s390_real_to_abs(vcpu, addr);
>   
> -	if (kvm_is_error_gpa(vcpu->kvm, addr))
> +	if (!kvm_is_gpa_in_memslot(vcpu->kvm, addr))
>   		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>   	/*
>   	 * We don't expect errors on modern systems, and do not care
> diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
> index d9696b530064..55c34cb35428 100644
> --- a/arch/s390/kvm/sigp.c
> +++ b/arch/s390/kvm/sigp.c
> @@ -172,7 +172,7 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, struct kvm_vcpu *dst_vcpu,
>   	 * first page, since address is 8k aligned and memory pieces are always
>   	 * at least 1MB aligned and have at least a size of 1MB.
>   	 */
> -	if (kvm_is_error_gpa(vcpu->kvm, irq.u.prefix.address)) {
> +	if (!kvm_is_gpa_in_memslot(vcpu->kvm, irq.u.prefix.address)) {
>   		*reg &= 0xffffffff00000000UL;
>   		*reg |= SIGP_STATUS_INVALID_PARAMETER;
>   		return SIGP_CC_STATUS_STORED;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7e7fd25b09b3..d175b64488ec 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1788,11 +1788,11 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
>   	return (hpa_t)pfn << PAGE_SHIFT;
>   }
>   
> -static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
> +static inline bool kvm_is_gpa_in_memslot(struct kvm *kvm, gpa_t gpa)
>   {
>   	unsigned long hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));
>   
> -	return kvm_is_error_hva(hva);
> +	return !kvm_is_error_hva(hva);
>   }
>   
>   enum kvm_stat_kind {
> 
> base-commit: 687d8f4c3dea0758afd748968d91288220bbe7e3
diff mbox series

Patch

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f2354f808d04..7994c4d16783 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1344,6 +1344,22 @@  void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm);
  */
 int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);
 
+/**
+ * kvm_gpc_activate_hva - prepare a cached kernel mapping and HPA for a given HVA.
+ *
+ * @gpc:          struct gfn_to_pfn_cache object.
+ * @hva:          userspace virtual address to map.
+ * @len:          sanity check; the range being access must fit a single page.
+ *
+ * @return:       0 for success.
+ *                -EINVAL for a mapping which would cross a page boundary.
+ *                -EFAULT for an untranslatable guest physical address.
+ *
+ * The semantics of this function are the same as those of kvm_gpc_activate(). It
+ * merely bypasses a layer of address translation.
+ */
+int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long hva, unsigned long len);
+
 /**
  * kvm_gpc_check - check validity of a gfn_to_pfn_cache.
  *
@@ -1398,7 +1414,9 @@  void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
 static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
 {
 	lockdep_assert_held(&gpc->lock);
-	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+
+	if (gpc->gpa != KVM_XEN_INVALID_GPA)
+		mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
 }
 
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 97eec8ee3449..ae822bff812f 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -48,7 +48,10 @@  bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
 	if (!gpc->active)
 		return false;
 
-	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
+	if (gpc->gpa != KVM_XEN_INVALID_GPA && gpc->generation != slots->generation)
+		return false;
+
+	if (kvm_is_error_hva(gpc->uhva))
 		return false;
 
 	if (offset_in_page(gpc->uhva) + len > PAGE_SIZE)
@@ -209,11 +212,13 @@  static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 	return -EFAULT;
 }
 
-static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
+static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,
 			     unsigned long len)
 {
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
-	unsigned long page_offset = offset_in_page(gpa);
+	unsigned long page_offset = (gpa != KVM_XEN_INVALID_GPA) ?
+		offset_in_page(gpa) :
+		offset_in_page(uhva);
 	bool unmap_old = false;
 	unsigned long old_uhva;
 	kvm_pfn_t old_pfn;
@@ -246,9 +251,15 @@  static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 	old_khva = (void *)PAGE_ALIGN_DOWN((uintptr_t)gpc->khva);
 	old_uhva = PAGE_ALIGN_DOWN(gpc->uhva);
 
-	/* Refresh the userspace HVA if necessary */
-	if (gpc->gpa != gpa || gpc->generation != slots->generation ||
-	    kvm_is_error_hva(gpc->uhva)) {
+	if (gpa == KVM_XEN_INVALID_GPA) {
+		gpc->gpa = KVM_XEN_INVALID_GPA;
+		gpc->uhva = PAGE_ALIGN_DOWN(uhva);
+
+		if (gpc->uhva != old_uhva)
+			hva_change = true;
+	} else if (gpc->gpa != gpa ||
+		   gpc->generation != slots->generation ||
+		   kvm_is_error_hva(gpc->uhva)) {
 		gfn_t gfn = gpa_to_gfn(gpa);
 
 		gpc->gpa = gpa;
@@ -319,7 +330,7 @@  static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 
 int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)
 {
-	return __kvm_gpc_refresh(gpc, gpc->gpa, len);
+	return __kvm_gpc_refresh(gpc, gpc->gpa, gpc->uhva, len);
 }
 
 void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
@@ -332,7 +343,8 @@  void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
 	gpc->uhva = KVM_HVA_ERR_BAD;
 }
 
-int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,
+			      unsigned long len)
 {
 	struct kvm *kvm = gpc->kvm;
 
@@ -353,7 +365,17 @@  int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 		gpc->active = true;
 		write_unlock_irq(&gpc->lock);
 	}
-	return __kvm_gpc_refresh(gpc, gpa, len);
+	return __kvm_gpc_refresh(gpc, gpa, uhva, len);
+}
+
+int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
+{
+	return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len);
+}
+
+int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long uhva, unsigned long len)
+{
+	return __kvm_gpc_activate(gpc, KVM_XEN_INVALID_GPA, uhva, len);
 }
 
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)