Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 3196 bytes --]

Hi,

On Tue, Jan 17, 2017 at 07:06:39PM +0800, jiang.biao2@zte.com.cn wrote:
> ＞ kvm_mips_map_page() will need to know whether the fault was due to a
> ＞ read or a write in order to support dirty page tracking,
> ＞ KVM_CAP_SYNC_MMU, and read only memory regions, so get that information
> ＞ passed down to it via new bool write_fault arguments to various
> ＞ functions.
> 
> Hi, James,
> 
> 
> Maybe it's not good idea to add an argument and pass it down to various functions,  it will ,
> 
> make the the interface more complicated,  have more possibolity, and more difficult to test.
> 

kvm_mips_map_page() needs to know is whether it is being triggered in
response to a write, but it is abstracted and independent from what host
exception triggered it. It is only really concerned with the GPA space.

> 
> 
> 
> As far as I can see,  what you need is to let kvm_mips_map_page() know the *reason*.
> 
> would it be better to let kvm_mips_map_page() get *exccode* from the CP0 directly, or 
> 
> 
> provide any interface to get the fault reason?

I presume you mean from the saved host cause register in the VCPU
context (since intervening exceptions/interrupts will clobber the actual
CP0 Cause register).

It directly needs to know whether it can get away with a read-only
mapping, and although it directly depends on a GVA segment, it doesn't
necessarily relate to a memory access made by the guest.

kvm_mips_map_page() is called via:

 - kvm_mips_handle_kseg0_tlb_fault()
   for faults in guest KSeg0

 - kvm_mips_handle_mapped_seg_tlb_fault()
   for faults in guest TLB mapped segments

From these functions:

 - kvm_trap_emul_handle_tlb_mod() (write_fault = true)
   in response to a write to a read-only page (exccode = MOD)

 - kvm_trap_emul_handle_tlb_miss() (write_fault = true or false)
   in response to a read or write when TLB mapping absent or invalid
   (exccode = TLBL/TLBS)

 - via the kvm_trap_emul_gva_fault() helper when KVM needs to directly
   access GVA space:

   - kvm_get_inst() (write_fault = false)
     when reading an instruction from guest RAM (when BadInstr/BadInstrP
     registers unavailable) which needs to be emulated, i.e. reserved
     instruction (exccode = RI), cop0 unusuable (exccode = CPU), MMIO
     load/store (TLBL/TLBS/MOD/ADEL/ADES), branch delay slot handling
     for MMIO load/store, or debug output for an unhandled exccode
     (exccode = ?)

   - kvm_mips_trans_replace() (write_fault = true)
     to write a replacement instruction into guest memory (mainly
     exccode = CPU)

   - kvm_mips_guest_cache_op() (write_fault = false)
     cache instruction emulation (exccode = CPU)

So there is a many:many mapping from exccode to write_fault for these
exccodes:

 - CPU (CoProcessor Unusable)
   could be reading instruction or servicing a CACHE instruction
   (write_fault = false) or replacing an instruction (write_fault =
   true).

 - MOD, TLBS, ADES
   could be the write itself (write_fault = true), or a read of the
   instruction triggering the exception or the prior branch instruction
   (write_fault = false).

Cheers
James

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 3196 bytes --]

Hi,

On Tue, Jan 17, 2017 at 07:06:39PM +0800, jiang.biao2@zte.com.cn wrote:
> ＞ kvm_mips_map_page() will need to know whether the fault was due to a
> ＞ read or a write in order to support dirty page tracking,
> ＞ KVM_CAP_SYNC_MMU, and read only memory regions, so get that information
> ＞ passed down to it via new bool write_fault arguments to various
> ＞ functions.
> 
> Hi, James,
> 
> 
> Maybe it's not good idea to add an argument and pass it down to various functions,  it will ,
> 
> make the the interface more complicated,  have more possibolity, and more difficult to test.
> 

kvm_mips_map_page() needs to know is whether it is being triggered in
response to a write, but it is abstracted and independent from what host
exception triggered it. It is only really concerned with the GPA space.

> 
> 
> 
> As far as I can see,  what you need is to let kvm_mips_map_page() know the *reason*.
> 
> would it be better to let kvm_mips_map_page() get *exccode* from the CP0 directly, or 
> 
> 
> provide any interface to get the fault reason?

I presume you mean from the saved host cause register in the VCPU
context (since intervening exceptions/interrupts will clobber the actual
CP0 Cause register).

It directly needs to know whether it can get away with a read-only
mapping, and although it directly depends on a GVA segment, it doesn't
necessarily relate to a memory access made by the guest.

kvm_mips_map_page() is called via:

 - kvm_mips_handle_kseg0_tlb_fault()
   for faults in guest KSeg0

 - kvm_mips_handle_mapped_seg_tlb_fault()
   for faults in guest TLB mapped segments

From these functions:

 - kvm_trap_emul_handle_tlb_mod() (write_fault = true)
   in response to a write to a read-only page (exccode = MOD)

 - kvm_trap_emul_handle_tlb_miss() (write_fault = true or false)
   in response to a read or write when TLB mapping absent or invalid
   (exccode = TLBL/TLBS)

 - via the kvm_trap_emul_gva_fault() helper when KVM needs to directly
   access GVA space:

   - kvm_get_inst() (write_fault = false)
     when reading an instruction from guest RAM (when BadInstr/BadInstrP
     registers unavailable) which needs to be emulated, i.e. reserved
     instruction (exccode = RI), cop0 unusuable (exccode = CPU), MMIO
     load/store (TLBL/TLBS/MOD/ADEL/ADES), branch delay slot handling
     for MMIO load/store, or debug output for an unhandled exccode
     (exccode = ?)

   - kvm_mips_trans_replace() (write_fault = true)
     to write a replacement instruction into guest memory (mainly
     exccode = CPU)

   - kvm_mips_guest_cache_op() (write_fault = false)
     cache instruction emulation (exccode = CPU)

So there is a many:many mapping from exccode to write_fault for these
exccodes:

 - CPU (CoProcessor Unusable)
   could be reading instruction or servicing a CACHE instruction
   (write_fault = false) or replacing an instruction (write_fault =
   true).

 - MOD, TLBS, ADES
   could be the write itself (write_fault = true), or a read of the
   instruction triggering the exception or the prior branch instruction
   (write_fault = false).

Cheers
James

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 1162 bytes --]

Hi,

On Thu, Jan 19, 2017 at 04:29:51PM +0800, jiang.biao2@zte.com.cn wrote:
> Hi, James
> 
> 
> 
> 
> 
> 
> 
> ＞ Whats wrong with bool parameters?
> ＞ 
> ＞ It needs a GPA mapping created, either for a read or a write depending
> ＞ on the caller. bool would seem ideally suited for just such a situation,
> ＞ and in fact its exactly what the KVM GPA fault code path does to pass
> ＞ whether the page needs to be writable:
> ＞ 
> ＞ kvm_mips_map_page() -＞ gfn_to_pfn_prot() -＞ __gfn_to_pfn_memslot() -＞
> ＞ hva_to_pfn() -＞ hva_to_pfn_slow().
> ＞ 
> ＞ so all this really does is extend that pattern up the other way as
> ＞ necessary to be able to provide that information to gfn_to_pfn_prot().
> Bool parameter may make the code less readable.  :-)
> 
> 
> The way used is indeed consistent with the exist pattern, but the tramp data 
> 
> 
> passed around and long parameters list maybe code smell(not for sure for 
> 
> 
> the kernel :-) ),  which may be improved by some means.
> 
> No offense,  just personal opinion. :-)

No offense taken :-)

Thanks again for reviewing,

Cheers
James

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 1162 bytes --]

Hi,

On Thu, Jan 19, 2017 at 04:29:51PM +0800, jiang.biao2@zte.com.cn wrote:
> Hi, James
> 
> 
> 
> 
> 
> 
> 
> ＞ Whats wrong with bool parameters?
> ＞ 
> ＞ It needs a GPA mapping created, either for a read or a write depending
> ＞ on the caller. bool would seem ideally suited for just such a situation,
> ＞ and in fact its exactly what the KVM GPA fault code path does to pass
> ＞ whether the page needs to be writable:
> ＞ 
> ＞ kvm_mips_map_page() -＞ gfn_to_pfn_prot() -＞ __gfn_to_pfn_memslot() -＞
> ＞ hva_to_pfn() -＞ hva_to_pfn_slow().
> ＞ 
> ＞ so all this really does is extend that pattern up the other way as
> ＞ necessary to be able to provide that information to gfn_to_pfn_prot().
> Bool parameter may make the code less readable.  :-)
> 
> 
> The way used is indeed consistent with the exist pattern, but the tramp data 
> 
> 
> passed around and long parameters list maybe code smell(not for sure for 
> 
> 
> the kernel :-) ),  which may be improved by some means.
> 
> No offense,  just personal opinion. :-)

No offense taken :-)

Thanks again for reviewing,

Cheers
James

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 2511 bytes --]

Hi,

On Wed, Jan 18, 2017 at 04:18:46PM +0800, jiang.biao2@zte.com.cn wrote:
> Hi,
> 
> ＞ I presume you mean from the saved host cause register in the VCPU
> ＞ context (since intervening exceptions/interrupts will clobber the actual
> ＞ CP0 Cause register).
> ＞ 
> ＞ It directly needs to know whether it can get away with a read-only
> ＞ mapping, and although it directly depends on a GVA segment, it doesn't
> ＞ necessarily relate to a memory access made by the guest.
> ＞ 
> ＞ kvm_mips_map_page() is called via:
> ＞ 
> ＞ - kvm_mips_handle_kseg0_tlb_fault()
> ＞   for faults in guest KSeg0
> ＞ 
> ＞  - kvm_mips_handle_mapped_seg_tlb_fault()
> ＞    for faults in guest TLB mapped segments
> ＞ 
> ＞ From these functions:
> ＞ 
> ＞  - kvm_trap_emul_handle_tlb_mod() (write_fault = true)
> ＞   in response to a write to a read-only page (exccode = MOD)
> ＞ 
> ＞ - kvm_trap_emul_handle_tlb_miss() (write_fault = true or false)
> ＞   in response to a read or write when TLB mapping absent or invalid
> ＞   (exccode = TLBL/TLBS)
> ＞
> ＞ 
> ＞ So there is a many:many mapping from exccode to write_fault for these
> ＞ exccodes:
> ＞ 
> ＞  - CPU (CoProcessor Unusable)
> ＞    could be reading instruction or servicing a CACHE instruction
> ＞    (write_fault = false) or replacing an instruction (write_fault =
> ＞    true).
> 
> ＞  - MOD, TLBS, ADES
> ＞   could be the write itself (write_fault = true), or a read of the
> ＞   instruction triggering the exception or the prior branch instruction
> ＞   (write_fault = false).
> ＞ 
> Thanks for the detail, it is more complicted than I thought.
> 
> But there may be still bad smell from the long parameters, espacially from 
> 
> 
> bool type ones.  

Whats wrong with bool parameters?

It needs a GPA mapping created, either for a read or a write depending
on the caller. bool would seem ideally suited for just such a situation,
and in fact its exactly what the KVM GPA fault code path does to pass
whether the page needs to be writable:

kvm_mips_map_page() -> gfn_to_pfn_prot() -> __gfn_to_pfn_memslot() ->
hva_to_pfn() -> hva_to_pfn_slow().

so all this really does is extend that pattern up the other way as
necessary to be able to provide that information to gfn_to_pfn_prot().

Cheers
James

> 
> 
> Maybe there is better way to handle that, but I can not figure it out right now 
> 
> 
> because of the complexity.

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 2511 bytes --]

Hi,

On Wed, Jan 18, 2017 at 04:18:46PM +0800, jiang.biao2@zte.com.cn wrote:
> Hi,
> 
> ＞ I presume you mean from the saved host cause register in the VCPU
> ＞ context (since intervening exceptions/interrupts will clobber the actual
> ＞ CP0 Cause register).
> ＞ 
> ＞ It directly needs to know whether it can get away with a read-only
> ＞ mapping, and although it directly depends on a GVA segment, it doesn't
> ＞ necessarily relate to a memory access made by the guest.
> ＞ 
> ＞ kvm_mips_map_page() is called via:
> ＞ 
> ＞ - kvm_mips_handle_kseg0_tlb_fault()
> ＞   for faults in guest KSeg0
> ＞ 
> ＞  - kvm_mips_handle_mapped_seg_tlb_fault()
> ＞    for faults in guest TLB mapped segments
> ＞ 
> ＞ From these functions:
> ＞ 
> ＞  - kvm_trap_emul_handle_tlb_mod() (write_fault = true)
> ＞   in response to a write to a read-only page (exccode = MOD)
> ＞ 
> ＞ - kvm_trap_emul_handle_tlb_miss() (write_fault = true or false)
> ＞   in response to a read or write when TLB mapping absent or invalid
> ＞   (exccode = TLBL/TLBS)
> ＞
> ＞ 
> ＞ So there is a many:many mapping from exccode to write_fault for these
> ＞ exccodes:
> ＞ 
> ＞  - CPU (CoProcessor Unusable)
> ＞    could be reading instruction or servicing a CACHE instruction
> ＞    (write_fault = false) or replacing an instruction (write_fault =
> ＞    true).
> 
> ＞  - MOD, TLBS, ADES
> ＞   could be the write itself (write_fault = true), or a read of the
> ＞   instruction triggering the exception or the prior branch instruction
> ＞   (write_fault = false).
> ＞ 
> Thanks for the detail, it is more complicted than I thought.
> 
> But there may be still bad smell from the long parameters, espacially from 
> 
> 
> bool type ones.  

Whats wrong with bool parameters?

It needs a GPA mapping created, either for a read or a write depending
on the caller. bool would seem ideally suited for just such a situation,
and in fact its exactly what the KVM GPA fault code path does to pass
whether the page needs to be writable:

kvm_mips_map_page() -> gfn_to_pfn_prot() -> __gfn_to_pfn_memslot() ->
hva_to_pfn() -> hva_to_pfn_slow().

so all this really does is extend that pattern up the other way as
necessary to be able to provide that information to gfn_to_pfn_prot().

Cheers
James

> 
> 
> Maybe there is better way to handle that, but I can not figure it out right now 
> 
> 
> because of the complexity.

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

[PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

kvm_mips_map_page() will need to know whether the fault was due to a
read or a write in order to support dirty page tracking,
KVM_CAP_SYNC_MMU, and read only memory regions, so get that information
passed down to it via new bool write_fault arguments to various
functions.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
---
 arch/mips/include/asm/kvm_host.h |  9 ++++++---
 arch/mips/kvm/emulate.c          |  7 ++++---
 arch/mips/kvm/mmu.c              | 21 +++++++++++++--------
 arch/mips/kvm/trap_emul.c        |  4 ++--
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index c24c1c23196b..70c2dd353468 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -597,19 +597,22 @@ u32 kvm_get_user_asid(struct kvm_vcpu *vcpu);
 u32 kvm_get_commpage_asid (struct kvm_vcpu *vcpu);
 
 extern int kvm_mips_handle_kseg0_tlb_fault(unsigned long badbaddr,
-					   struct kvm_vcpu *vcpu);
+					   struct kvm_vcpu *vcpu,
+					   bool write_fault);
 
 extern int kvm_mips_handle_commpage_tlb_fault(unsigned long badvaddr,
 					      struct kvm_vcpu *vcpu);
 
 extern int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 						struct kvm_mips_tlb *tlb,
-						unsigned long gva);
+						unsigned long gva,
+						bool write_fault);
 
 extern enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 						     u32 *opc,
 						     struct kvm_run *run,
-						     struct kvm_vcpu *vcpu);
+						     struct kvm_vcpu *vcpu,
+						     bool write_fault);
 
 extern enum emulation_result kvm_mips_handle_tlbmod(u32 cause,
 						    u32 *opc,
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 72eb307a61a7..a47f8af9193e 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -2705,7 +2705,8 @@ enum emulation_result kvm_mips_check_privilege(u32 cause,
 enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 					      u32 *opc,
 					      struct kvm_run *run,
-					      struct kvm_vcpu *vcpu)
+					      struct kvm_vcpu *vcpu,
+					      bool write_fault)
 {
 	enum emulation_result er = EMULATE_DONE;
 	u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
@@ -2761,8 +2762,8 @@ enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 			 * OK we have a Guest TLB entry, now inject it into the
 			 * shadow host TLB
 			 */
-			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
-								 va)) {
+			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, va,
+								 write_fault)) {
 				kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
 					__func__, va, index, vcpu,
 					read_c0_entryhi());
diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index b3da473e1569..1af65f2e6bb7 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -308,6 +308,7 @@ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
  * kvm_mips_map_page() - Map a guest physical page.
  * @vcpu:		VCPU pointer.
  * @gpa:		Guest physical address of fault.
+ * @write_fault:	Whether the fault was due to a write.
  * @out_entry:		New PTE for @gpa (written on success unless NULL).
  * @out_buddy:		New PTE for @gpa's buddy (written on success unless
  *			NULL).
@@ -327,6 +328,7 @@ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
  *		as an MMIO access.
  */
 static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
+			     bool write_fault,
 			     pte_t *out_entry, pte_t *out_buddy)
 {
 	struct kvm *kvm = vcpu->kvm;
@@ -558,7 +560,8 @@ void kvm_mips_flush_gva_pt(pgd_t *pgd, enum kvm_mips_flush flags)
 
 /* XXXKYMA: Must be called with interrupts disabled */
 int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
-				    struct kvm_vcpu *vcpu)
+				    struct kvm_vcpu *vcpu,
+				    bool write_fault)
 {
 	unsigned long gpa;
 	kvm_pfn_t pfn0, pfn1;
@@ -576,10 +579,11 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
 	gpa = KVM_GUEST_CPHYSADDR(badvaddr & (PAGE_MASK << 1));
 	vaddr = badvaddr & (PAGE_MASK << 1);
 
-	if (kvm_mips_map_page(vcpu, gpa, &pte_gpa[0], NULL) < 0)
+	if (kvm_mips_map_page(vcpu, gpa, write_fault, &pte_gpa[0], NULL) < 0)
 		return -1;
 
-	if (kvm_mips_map_page(vcpu, gpa | PAGE_SIZE, &pte_gpa[1], NULL) < 0)
+	if (kvm_mips_map_page(vcpu, gpa | PAGE_SIZE, write_fault, &pte_gpa[1],
+			      NULL) < 0)
 		return -1;
 
 	pfn0 = pte_pfn(pte_gpa[0]);
@@ -604,7 +608,8 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
 
 int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 					 struct kvm_mips_tlb *tlb,
-					 unsigned long gva)
+					 unsigned long gva,
+					 bool write_fault)
 {
 	kvm_pfn_t pfn;
 	long tlb_lo = 0;
@@ -621,8 +626,8 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 		tlb_lo = tlb->tlb_lo[idx];
 
 	/* Find host PFN */
-	if (kvm_mips_map_page(vcpu, mips3_tlbpfn_to_paddr(tlb_lo), &pte_gpa,
-			      NULL) < 0)
+	if (kvm_mips_map_page(vcpu, mips3_tlbpfn_to_paddr(tlb_lo), write_fault,
+			      &pte_gpa, NULL) < 0)
 		return -1;
 	pfn = pte_pfn(pte_gpa);
 
@@ -757,7 +762,7 @@ enum kvm_mips_fault_result kvm_trap_emul_gva_fault(struct kvm_vcpu *vcpu,
 	int index;
 
 	if (KVM_GUEST_KSEGX(gva) == KVM_GUEST_KSEG0) {
-		if (kvm_mips_handle_kseg0_tlb_fault(gva, vcpu) < 0)
+		if (kvm_mips_handle_kseg0_tlb_fault(gva, vcpu, write) < 0)
 			return KVM_MIPS_GPA;
 	} else if ((KVM_GUEST_KSEGX(gva) < KVM_GUEST_KSEG0) ||
 		   KVM_GUEST_KSEGX(gva) == KVM_GUEST_KSEG23) {
@@ -774,7 +779,7 @@ enum kvm_mips_fault_result kvm_trap_emul_gva_fault(struct kvm_vcpu *vcpu,
 		if (write && !TLB_IS_DIRTY(*tlb, gva))
 			return KVM_MIPS_TLBMOD;
 
-		if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, gva))
+		if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, gva, write))
 			return KVM_MIPS_GPA;
 	} else {
 		return KVM_MIPS_GVA;
diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index 970ab216b355..33888f1a89f4 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -159,7 +159,7 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
 		 *     into the shadow host TLB
 		 */
 
-		er = kvm_mips_handle_tlbmiss(cause, opc, run, vcpu);
+		er = kvm_mips_handle_tlbmiss(cause, opc, run, vcpu, store);
 		if (er == EMULATE_DONE)
 			ret = RESUME_GUEST;
 		else {
@@ -172,7 +172,7 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
 		 * not expect to ever get them
 		 */
 		if (kvm_mips_handle_kseg0_tlb_fault
-		    (vcpu->arch.host_cp0_badvaddr, vcpu) < 0) {
+		    (vcpu->arch.host_cp0_badvaddr, vcpu, store) < 0) {
 			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 			ret = RESUME_HOST;
 		}
-- 
git-series 0.8.10

[PATCH 2/13] KVM: MIPS: Pass type of fault down to kvm_mips_map_page()

[James Hogan]

kvm_mips_map_page() will need to know whether the fault was due to a
read or a write in order to support dirty page tracking,
KVM_CAP_SYNC_MMU, and read only memory regions, so get that information
passed down to it via new bool write_fault arguments to various
functions.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
---
 arch/mips/include/asm/kvm_host.h |  9 ++++++---
 arch/mips/kvm/emulate.c          |  7 ++++---
 arch/mips/kvm/mmu.c              | 21 +++++++++++++--------
 arch/mips/kvm/trap_emul.c        |  4 ++--
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index c24c1c23196b..70c2dd353468 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -597,19 +597,22 @@ u32 kvm_get_user_asid(struct kvm_vcpu *vcpu);
 u32 kvm_get_commpage_asid (struct kvm_vcpu *vcpu);
 
 extern int kvm_mips_handle_kseg0_tlb_fault(unsigned long badbaddr,
-					   struct kvm_vcpu *vcpu);
+					   struct kvm_vcpu *vcpu,
+					   bool write_fault);
 
 extern int kvm_mips_handle_commpage_tlb_fault(unsigned long badvaddr,
 					      struct kvm_vcpu *vcpu);
 
 extern int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 						struct kvm_mips_tlb *tlb,
-						unsigned long gva);
+						unsigned long gva,
+						bool write_fault);
 
 extern enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 						     u32 *opc,
 						     struct kvm_run *run,
-						     struct kvm_vcpu *vcpu);
+						     struct kvm_vcpu *vcpu,
+						     bool write_fault);
 
 extern enum emulation_result kvm_mips_handle_tlbmod(u32 cause,
 						    u32 *opc,
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 72eb307a61a7..a47f8af9193e 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -2705,7 +2705,8 @@ enum emulation_result kvm_mips_check_privilege(u32 cause,
 enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 					      u32 *opc,
 					      struct kvm_run *run,
-					      struct kvm_vcpu *vcpu)
+					      struct kvm_vcpu *vcpu,
+					      bool write_fault)
 {
 	enum emulation_result er = EMULATE_DONE;
 	u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
@@ -2761,8 +2762,8 @@ enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
 			 * OK we have a Guest TLB entry, now inject it into the
 			 * shadow host TLB
 			 */
-			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
-								 va)) {
+			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, va,
+								 write_fault)) {
 				kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
 					__func__, va, index, vcpu,
 					read_c0_entryhi());
diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index b3da473e1569..1af65f2e6bb7 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -308,6 +308,7 @@ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
  * kvm_mips_map_page() - Map a guest physical page.
  * @vcpu:		VCPU pointer.
  * @gpa:		Guest physical address of fault.
+ * @write_fault:	Whether the fault was due to a write.
  * @out_entry:		New PTE for @gpa (written on success unless NULL).
  * @out_buddy:		New PTE for @gpa's buddy (written on success unless
  *			NULL).
@@ -327,6 +328,7 @@ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
  *		as an MMIO access.
  */
 static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
+			     bool write_fault,
 			     pte_t *out_entry, pte_t *out_buddy)
 {
 	struct kvm *kvm = vcpu->kvm;
@@ -558,7 +560,8 @@ void kvm_mips_flush_gva_pt(pgd_t *pgd, enum kvm_mips_flush flags)
 
 /* XXXKYMA: Must be called with interrupts disabled */
 int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
-				    struct kvm_vcpu *vcpu)
+				    struct kvm_vcpu *vcpu,
+				    bool write_fault)
 {
 	unsigned long gpa;
 	kvm_pfn_t pfn0, pfn1;
@@ -576,10 +579,11 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
 	gpa = KVM_GUEST_CPHYSADDR(badvaddr & (PAGE_MASK << 1));
 	vaddr = badvaddr & (PAGE_MASK << 1);
 
-	if (kvm_mips_map_page(vcpu, gpa, &pte_gpa[0], NULL) < 0)
+	if (kvm_mips_map_page(vcpu, gpa, write_fault, &pte_gpa[0], NULL) < 0)
 		return -1;
 
-	if (kvm_mips_map_page(vcpu, gpa | PAGE_SIZE, &pte_gpa[1], NULL) < 0)
+	if (kvm_mips_map_page(vcpu, gpa | PAGE_SIZE, write_fault, &pte_gpa[1],
+			      NULL) < 0)
 		return -1;
 
 	pfn0 = pte_pfn(pte_gpa[0]);
@@ -604,7 +608,8 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
 
 int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 					 struct kvm_mips_tlb *tlb,
-					 unsigned long gva)
+					 unsigned long gva,
+					 bool write_fault)
 {
 	kvm_pfn_t pfn;
 	long tlb_lo = 0;
@@ -621,8 +626,8 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 		tlb_lo = tlb->tlb_lo[idx];
 
 	/* Find host PFN */
-	if (kvm_mips_map_page(vcpu, mips3_tlbpfn_to_paddr(tlb_lo), &pte_gpa,
-			      NULL) < 0)
+	if (kvm_mips_map_page(vcpu, mips3_tlbpfn_to_paddr(tlb_lo), write_fault,
+			      &pte_gpa, NULL) < 0)
 		return -1;
 	pfn = pte_pfn(pte_gpa);
 
@@ -757,7 +762,7 @@ enum kvm_mips_fault_result kvm_trap_emul_gva_fault(struct kvm_vcpu *vcpu,
 	int index;
 
 	if (KVM_GUEST_KSEGX(gva) == KVM_GUEST_KSEG0) {
-		if (kvm_mips_handle_kseg0_tlb_fault(gva, vcpu) < 0)
+		if (kvm_mips_handle_kseg0_tlb_fault(gva, vcpu, write) < 0)
 			return KVM_MIPS_GPA;
 	} else if ((KVM_GUEST_KSEGX(gva) < KVM_GUEST_KSEG0) ||
 		   KVM_GUEST_KSEGX(gva) == KVM_GUEST_KSEG23) {
@@ -774,7 +779,7 @@ enum kvm_mips_fault_result kvm_trap_emul_gva_fault(struct kvm_vcpu *vcpu,
 		if (write && !TLB_IS_DIRTY(*tlb, gva))
 			return KVM_MIPS_TLBMOD;
 
-		if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, gva))
+		if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, gva, write))
 			return KVM_MIPS_GPA;
 	} else {
 		return KVM_MIPS_GVA;
diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index 970ab216b355..33888f1a89f4 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -159,7 +159,7 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
 		 *     into the shadow host TLB
 		 */
 
-		er = kvm_mips_handle_tlbmiss(cause, opc, run, vcpu);
+		er = kvm_mips_handle_tlbmiss(cause, opc, run, vcpu, store);
 		if (er == EMULATE_DONE)
 			ret = RESUME_GUEST;
 		else {
@@ -172,7 +172,7 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
 		 * not expect to ever get them
 		 */
 		if (kvm_mips_handle_kseg0_tlb_fault
-		    (vcpu->arch.host_cp0_badvaddr, vcpu) < 0) {
+		    (vcpu->arch.host_cp0_badvaddr, vcpu, store) < 0) {
 			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 			ret = RESUME_HOST;
 		}
-- 
git-series 0.8.10