Patchwork [4/6,v5] kvm: powerpc: keep only pte search logic in lookup_linux_pte

login
register
mail settings
Submitter Bharat Bhushan
Date Sept. 19, 2013, 6:02 a.m.
Message ID <1379570566-3715-5-git-send-email-Bharat.Bhushan@freescale.com>
Download mbox | patch
Permalink /patch/275878/
State Not Applicable
Headers show

Comments

Bharat Bhushan - Sept. 19, 2013, 6:02 a.m.
lookup_linux_pte() was searching for a pte and also sets access
flags is writable. This function now searches only pte while
access flag setting is done explicitly.

This pte lookup is not kvm specific, so moved to common code (asm/pgtable.h)
My Followup patch will use this on booke.

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v4->v5
 - No change

 arch/powerpc/include/asm/pgtable.h  |   24 +++++++++++++++++++++++
 arch/powerpc/kvm/book3s_hv_rm_mmu.c |   36 +++++++++++-----------------------
 2 files changed, 36 insertions(+), 24 deletions(-)
Alexander Graf - Oct. 4, 2013, 1:27 p.m.
On 19.09.2013, at 08:02, Bharat Bhushan wrote:

> lookup_linux_pte() was searching for a pte and also sets access
> flags is writable. This function now searches only pte while
> access flag setting is done explicitly.
> 
> This pte lookup is not kvm specific, so moved to common code (asm/pgtable.h)
> My Followup patch will use this on booke.
> 
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
> v4->v5
> - No change
> 
> arch/powerpc/include/asm/pgtable.h  |   24 +++++++++++++++++++++++
> arch/powerpc/kvm/book3s_hv_rm_mmu.c |   36 +++++++++++-----------------------
> 2 files changed, 36 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 7d6eacf..3a5de5c 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -223,6 +223,30 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
> #endif
> pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
> 				 unsigned *shift);
> +
> +static inline pte_t *lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
> +				     unsigned long *pte_sizep)
> +{
> +	pte_t *ptep;
> +	unsigned long ps = *pte_sizep;
> +	unsigned int shift;
> +
> +	ptep = find_linux_pte_or_hugepte(pgdir, hva, &shift);
> +	if (!ptep)
> +		return __pte(0);

This returns a struct pte_t, but your return value of the function is a struct pte_t *. So this code will fail compiling with STRICT_MM_TYPECHECKS set. Any reason you don't just return NULL here?

That way callers could simply check on if (ptep) ... or you leave the return value as struct pte_t.


Alex

> +	if (shift)
> +		*pte_sizep = 1ul << shift;
> +	else
> +		*pte_sizep = PAGE_SIZE;
> +
> +	if (ps > *pte_sizep)
> +		return __pte(0);
> +
> +	if (!pte_present(*ptep))
> +		return __pte(0);

> +
> +	return ptep;
> +}
> #endif /* __ASSEMBLY__ */
> 
> #endif /* __KERNEL__ */
> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> index 45e30d6..74fa7f8 100644
> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> @@ -134,25 +134,6 @@ static void remove_revmap_chain(struct kvm *kvm, long pte_index,
> 	unlock_rmap(rmap);
> }
> 
> -static pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
> -			      int writing, unsigned long *pte_sizep)
> -{
> -	pte_t *ptep;
> -	unsigned long ps = *pte_sizep;
> -	unsigned int hugepage_shift;
> -
> -	ptep = find_linux_pte_or_hugepte(pgdir, hva, &hugepage_shift);
> -	if (!ptep)
> -		return __pte(0);
> -	if (hugepage_shift)
> -		*pte_sizep = 1ul << hugepage_shift;
> -	else
> -		*pte_sizep = PAGE_SIZE;
> -	if (ps > *pte_sizep)
> -		return __pte(0);
> -	return kvmppc_read_update_linux_pte(ptep, writing, hugepage_shift);
> -}
> -
> static inline void unlock_hpte(unsigned long *hpte, unsigned long hpte_v)
> {
> 	asm volatile(PPC_RELEASE_BARRIER "" : : : "memory");
> @@ -173,6 +154,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
> 	unsigned long is_io;
> 	unsigned long *rmap;
> 	pte_t pte;
> +	pte_t *ptep;
> 	unsigned int writing;
> 	unsigned long mmu_seq;
> 	unsigned long rcbits;
> @@ -231,8 +213,9 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
> 
> 		/* Look up the Linux PTE for the backing page */
> 		pte_size = psize;
> -		pte = lookup_linux_pte(pgdir, hva, writing, &pte_size);
> -		if (pte_present(pte)) {
> +		ptep = lookup_linux_pte(pgdir, hva, &pte_size);
> +		if (pte_present(pte_val(*ptep))) {
> +			pte = kvmppc_read_update_linux_pte(ptep, writing);
> 			if (writing && !pte_write(pte))
> 				/* make the actual HPTE be read-only */
> 				ptel = hpte_make_readonly(ptel);
> @@ -661,15 +644,20 @@ long kvmppc_h_protect(struct kvm_vcpu *vcpu, unsigned long flags,
> 			struct kvm_memory_slot *memslot;
> 			pgd_t *pgdir = vcpu->arch.pgdir;
> 			pte_t pte;
> +			pte_t *ptep;
> 
> 			psize = hpte_page_size(v, r);
> 			gfn = ((r & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
> 			memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
> 			if (memslot) {
> 				hva = __gfn_to_hva_memslot(memslot, gfn);
> -				pte = lookup_linux_pte(pgdir, hva, 1, &psize);
> -				if (pte_present(pte) && !pte_write(pte))
> -					r = hpte_make_readonly(r);
> +				ptep = lookup_linux_pte(pgdir, hva, &psize);
> +				if (pte_present(pte_val(*ptep))) {
> +					pte = kvmppc_read_update_linux_pte(ptep,
> +									   1);
> +					if (pte_present(pte) && !pte_write(pte))
> +						r = hpte_make_readonly(r);
> +				}
> 			}
> 		}
> 	}
> -- 
> 1.7.0.4
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
Bharat Bhushan - Oct. 4, 2013, 1:44 p.m.
> -----Original Message-----
> From: Alexander Graf [mailto:agraf@suse.de]
> Sent: Friday, October 04, 2013 6:57 PM
> To: Bhushan Bharat-R65777
> Cc: benh@kernel.crashing.org; paulus@samba.org; kvm@vger.kernel.org; kvm-
> ppc@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; Wood Scott-B07421; Bhushan
> Bharat-R65777
> Subject: Re: [PATCH 4/6 v5] kvm: powerpc: keep only pte search logic in
> lookup_linux_pte
> 
> 
> On 19.09.2013, at 08:02, Bharat Bhushan wrote:
> 
> > lookup_linux_pte() was searching for a pte and also sets access flags
> > is writable. This function now searches only pte while access flag
> > setting is done explicitly.
> >
> > This pte lookup is not kvm specific, so moved to common code
> > (asm/pgtable.h) My Followup patch will use this on booke.
> >
> > Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> > ---
> > v4->v5
> > - No change
> >
> > arch/powerpc/include/asm/pgtable.h  |   24 +++++++++++++++++++++++
> > arch/powerpc/kvm/book3s_hv_rm_mmu.c |   36 +++++++++++-----------------------
> > 2 files changed, 36 insertions(+), 24 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/pgtable.h
> > b/arch/powerpc/include/asm/pgtable.h
> > index 7d6eacf..3a5de5c 100644
> > --- a/arch/powerpc/include/asm/pgtable.h
> > +++ b/arch/powerpc/include/asm/pgtable.h
> > @@ -223,6 +223,30 @@ extern int gup_hugepte(pte_t *ptep, unsigned long
> > sz, unsigned long addr, #endif pte_t *find_linux_pte_or_hugepte(pgd_t
> > *pgdir, unsigned long ea,
> > 				 unsigned *shift);
> > +
> > +static inline pte_t *lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
> > +				     unsigned long *pte_sizep)
> > +{
> > +	pte_t *ptep;
> > +	unsigned long ps = *pte_sizep;
> > +	unsigned int shift;
> > +
> > +	ptep = find_linux_pte_or_hugepte(pgdir, hva, &shift);
> > +	if (!ptep)
> > +		return __pte(0);
> 
> This returns a struct pte_t, but your return value of the function is a struct
> pte_t *. So this code will fail compiling with STRICT_MM_TYPECHECKS set. Any
> reason you don't just return NULL here?

I want to return the ptep (pte pointer) , so yes this should be NULL.
Will correct this.

Thanks
-Bharat

> 
> That way callers could simply check on if (ptep) ... or you leave the return
> value as struct pte_t.
> 
> 
> Alex
> 
> > +	if (shift)
> > +		*pte_sizep = 1ul << shift;
> > +	else
> > +		*pte_sizep = PAGE_SIZE;
> > +
> > +	if (ps > *pte_sizep)
> > +		return __pte(0);
> > +
> > +	if (!pte_present(*ptep))
> > +		return __pte(0);
> 
> > +
> > +	return ptep;
> > +}
> > #endif /* __ASSEMBLY__ */
> >
> > #endif /* __KERNEL__ */
> > diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> > b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> > index 45e30d6..74fa7f8 100644
> > --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> > +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> > @@ -134,25 +134,6 @@ static void remove_revmap_chain(struct kvm *kvm, long
> pte_index,
> > 	unlock_rmap(rmap);
> > }
> >
> > -static pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
> > -			      int writing, unsigned long *pte_sizep)
> > -{
> > -	pte_t *ptep;
> > -	unsigned long ps = *pte_sizep;
> > -	unsigned int hugepage_shift;
> > -
> > -	ptep = find_linux_pte_or_hugepte(pgdir, hva, &hugepage_shift);
> > -	if (!ptep)
> > -		return __pte(0);
> > -	if (hugepage_shift)
> > -		*pte_sizep = 1ul << hugepage_shift;
> > -	else
> > -		*pte_sizep = PAGE_SIZE;
> > -	if (ps > *pte_sizep)
> > -		return __pte(0);
> > -	return kvmppc_read_update_linux_pte(ptep, writing, hugepage_shift);
> > -}
> > -
> > static inline void unlock_hpte(unsigned long *hpte, unsigned long
> > hpte_v) {
> > 	asm volatile(PPC_RELEASE_BARRIER "" : : : "memory"); @@ -173,6 +154,7
> > @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
> > 	unsigned long is_io;
> > 	unsigned long *rmap;
> > 	pte_t pte;
> > +	pte_t *ptep;
> > 	unsigned int writing;
> > 	unsigned long mmu_seq;
> > 	unsigned long rcbits;
> > @@ -231,8 +213,9 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned
> > long flags,
> >
> > 		/* Look up the Linux PTE for the backing page */
> > 		pte_size = psize;
> > -		pte = lookup_linux_pte(pgdir, hva, writing, &pte_size);
> > -		if (pte_present(pte)) {
> > +		ptep = lookup_linux_pte(pgdir, hva, &pte_size);
> > +		if (pte_present(pte_val(*ptep))) {
> > +			pte = kvmppc_read_update_linux_pte(ptep, writing);
> > 			if (writing && !pte_write(pte))
> > 				/* make the actual HPTE be read-only */
> > 				ptel = hpte_make_readonly(ptel);
> > @@ -661,15 +644,20 @@ long kvmppc_h_protect(struct kvm_vcpu *vcpu, unsigned
> long flags,
> > 			struct kvm_memory_slot *memslot;
> > 			pgd_t *pgdir = vcpu->arch.pgdir;
> > 			pte_t pte;
> > +			pte_t *ptep;
> >
> > 			psize = hpte_page_size(v, r);
> > 			gfn = ((r & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
> > 			memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
> > 			if (memslot) {
> > 				hva = __gfn_to_hva_memslot(memslot, gfn);
> > -				pte = lookup_linux_pte(pgdir, hva, 1, &psize);
> > -				if (pte_present(pte) && !pte_write(pte))
> > -					r = hpte_make_readonly(r);
> > +				ptep = lookup_linux_pte(pgdir, hva, &psize);
> > +				if (pte_present(pte_val(*ptep))) {
> > +					pte = kvmppc_read_update_linux_pte(ptep,
> > +									   1);
> > +					if (pte_present(pte) && !pte_write(pte))
> > +						r = hpte_make_readonly(r);
> > +				}
> > 			}
> > 		}
> > 	}
> > --
> > 1.7.0.4
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
> > the body of a message to majordomo@vger.kernel.org More majordomo info
> > at  http://vger.kernel.org/majordomo-info.html
>

Patch

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..3a5de5c 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,30 @@  extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 #endif
 pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
 				 unsigned *shift);
+
+static inline pte_t *lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+				     unsigned long *pte_sizep)
+{
+	pte_t *ptep;
+	unsigned long ps = *pte_sizep;
+	unsigned int shift;
+
+	ptep = find_linux_pte_or_hugepte(pgdir, hva, &shift);
+	if (!ptep)
+		return __pte(0);
+	if (shift)
+		*pte_sizep = 1ul << shift;
+	else
+		*pte_sizep = PAGE_SIZE;
+
+	if (ps > *pte_sizep)
+		return __pte(0);
+
+	if (!pte_present(*ptep))
+		return __pte(0);
+
+	return ptep;
+}
 #endif /* __ASSEMBLY__ */
 
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 45e30d6..74fa7f8 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -134,25 +134,6 @@  static void remove_revmap_chain(struct kvm *kvm, long pte_index,
 	unlock_rmap(rmap);
 }
 
-static pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
-			      int writing, unsigned long *pte_sizep)
-{
-	pte_t *ptep;
-	unsigned long ps = *pte_sizep;
-	unsigned int hugepage_shift;
-
-	ptep = find_linux_pte_or_hugepte(pgdir, hva, &hugepage_shift);
-	if (!ptep)
-		return __pte(0);
-	if (hugepage_shift)
-		*pte_sizep = 1ul << hugepage_shift;
-	else
-		*pte_sizep = PAGE_SIZE;
-	if (ps > *pte_sizep)
-		return __pte(0);
-	return kvmppc_read_update_linux_pte(ptep, writing, hugepage_shift);
-}
-
 static inline void unlock_hpte(unsigned long *hpte, unsigned long hpte_v)
 {
 	asm volatile(PPC_RELEASE_BARRIER "" : : : "memory");
@@ -173,6 +154,7 @@  long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
 	unsigned long is_io;
 	unsigned long *rmap;
 	pte_t pte;
+	pte_t *ptep;
 	unsigned int writing;
 	unsigned long mmu_seq;
 	unsigned long rcbits;
@@ -231,8 +213,9 @@  long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
 
 		/* Look up the Linux PTE for the backing page */
 		pte_size = psize;
-		pte = lookup_linux_pte(pgdir, hva, writing, &pte_size);
-		if (pte_present(pte)) {
+		ptep = lookup_linux_pte(pgdir, hva, &pte_size);
+		if (pte_present(pte_val(*ptep))) {
+			pte = kvmppc_read_update_linux_pte(ptep, writing);
 			if (writing && !pte_write(pte))
 				/* make the actual HPTE be read-only */
 				ptel = hpte_make_readonly(ptel);
@@ -661,15 +644,20 @@  long kvmppc_h_protect(struct kvm_vcpu *vcpu, unsigned long flags,
 			struct kvm_memory_slot *memslot;
 			pgd_t *pgdir = vcpu->arch.pgdir;
 			pte_t pte;
+			pte_t *ptep;
 
 			psize = hpte_page_size(v, r);
 			gfn = ((r & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
 			memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
 			if (memslot) {
 				hva = __gfn_to_hva_memslot(memslot, gfn);
-				pte = lookup_linux_pte(pgdir, hva, 1, &psize);
-				if (pte_present(pte) && !pte_write(pte))
-					r = hpte_make_readonly(r);
+				ptep = lookup_linux_pte(pgdir, hva, &psize);
+				if (pte_present(pte_val(*ptep))) {
+					pte = kvmppc_read_update_linux_pte(ptep,
+									   1);
+					if (pte_present(pte) && !pte_write(pte))
+						r = hpte_make_readonly(r);
+				}
 			}
 		}
 	}