Re: [PATCH 2/4] kvm: Merge "atomic" and "write" in __gfn_to_pfn_memslot()

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On 6/22/22 14:36, Peter Xu wrote:
Merge two boolean parameters into a bitmask flag called kvm_gtp_flag_t for
__gfn_to_pfn_memslot().  This cleans the parameter lists, and also prepare
for new boolean to be added to __gfn_to_pfn_memslot().

Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
  arch/arm64/kvm/mmu.c                   |  5 ++--
  arch/powerpc/kvm/book3s_64_mmu_hv.c    |  5 ++--
  arch/powerpc/kvm/book3s_64_mmu_radix.c |  5 ++--
  arch/x86/kvm/mmu/mmu.c                 | 10 +++----
  include/linux/kvm_host.h               |  9 ++++++-
  virt/kvm/kvm_main.c                    | 37 +++++++++++++++-----------
  virt/kvm/kvm_mm.h                      |  6 +++--
  virt/kvm/pfncache.c                    |  2 +-
  8 files changed, 49 insertions(+), 30 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f5651a05b6a8..ce1edb512b4e 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1204,8 +1204,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
  	 */
  	smp_rmb();
- pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
-				   write_fault, &writable, NULL);
+	pfn = __gfn_to_pfn_memslot(memslot, gfn,
+				   write_fault ? KVM_GTP_WRITE : 0,
+				   NULL, &writable, NULL);
  	if (pfn == KVM_PFN_ERR_HWPOISON) {
  		kvm_send_hwpoison_signal(hva, vma_shift);
  		return 0;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 514fd45c1994..e2769d58dd87 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -598,8 +598,9 @@ int kvmppc_book3s_hv_page_fault(struct kvm_vcpu *vcpu,
  		write_ok = true;
  	} else {
  		/* Call KVM generic code to do the slow-path check */
-		pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
-					   writing, &write_ok, NULL);
+		pfn = __gfn_to_pfn_memslot(memslot, gfn,
+					   writing ? KVM_GTP_WRITE : 0,
+					   NULL, &write_ok, NULL);
  		if (is_error_noslot_pfn(pfn))
  			return -EFAULT;
  		page = NULL;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 42851c32ff3b..232b17c75b83 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -845,8 +845,9 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
  		unsigned long pfn;
/* Call KVM generic code to do the slow-path check */
-		pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
-					   writing, upgrade_p, NULL);
+		pfn = __gfn_to_pfn_memslot(memslot, gfn,
+					   writing ? KVM_GTP_WRITE : 0,
+					   NULL, upgrade_p, NULL);
  		if (is_error_noslot_pfn(pfn))
  			return -EFAULT;
  		page = NULL;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index f4653688fa6d..e92f1ab63d6a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3968,6 +3968,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
  {
+	kvm_gtp_flag_t flags = fault->write ? KVM_GTP_WRITE : 0;
  	struct kvm_memory_slot *slot = fault->slot;
  	bool async;
@@ -3999,8 +4000,8 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
  	}
async = false;
-	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, &async,
-					  fault->write, &fault->map_writable,
+	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, flags,
+					  &async, &fault->map_writable,
  					  &fault->hva);
  	if (!async)
  		return RET_PF_CONTINUE; /* *pfn has correct page already */
@@ -4016,9 +4017,8 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
  		}
  	}
- fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, NULL,
-					  fault->write, &fault->map_writable,
-					  &fault->hva);
+	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, flags, NULL,
+					  &fault->map_writable, &fault->hva);

The flags arg does improve the situation, yes.

  	return RET_PF_CONTINUE;
  }
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c20f2d55840c..b646b6fcaec6 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1146,8 +1146,15 @@ kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
  		      bool *writable);
  kvm_pfn_t gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn);
  kvm_pfn_t gfn_to_pfn_memslot_atomic(const struct kvm_memory_slot *slot, gfn_t gfn);
+
+/* gfn_to_pfn (gtp) flags */
+typedef unsigned int __bitwise kvm_gtp_flag_t;

A minor naming problem: GTP and especially gtp_flags is way too close
to gfp_flags. It will make people either wonder if it's a typo, or
worse, *assume* that it's a typo. :)

Yes, "read the code", but if you can come up with a better TLA than GTP
here, let's consider using it.

Overall, the change looks like an improvement, even though

    write_fault ? KVM_GTP_WRITE : 0

is not wonderful. But improving *that* leads to a a big pile of diffs
that are rather beyond the scope here.


thanks,
--
John Hubbard
NVIDIA


+
+#define  KVM_GTP_WRITE          ((__force kvm_gtp_flag_t) BIT(0))
+#define  KVM_GTP_ATOMIC         ((__force kvm_gtp_flag_t) BIT(1))
+
  kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
-			       bool atomic, bool *async, bool write_fault,
+			       kvm_gtp_flag_t gtp_flags, bool *async,
  			       bool *writable, hva_t *hva);
void kvm_release_pfn_clean(kvm_pfn_t pfn);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 64ec2222a196..952400b42ee9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2444,9 +2444,11 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
   * The slow path to get the pfn of the specified host virtual address,
   * 1 indicates success, -errno is returned if error is detected.
   */
-static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
+static int hva_to_pfn_slow(unsigned long addr, bool *async,
+			   kvm_gtp_flag_t gtp_flags,
  			   bool *writable, kvm_pfn_t *pfn)
  {
+	bool write_fault = gtp_flags & KVM_GTP_WRITE;
  	unsigned int flags = FOLL_HWPOISON;
  	struct page *page;
  	int npages = 0;
@@ -2565,20 +2567,22 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
  /*
   * Pin guest page in memory and return its pfn.
   * @addr: host virtual address which maps memory to the guest
- * @atomic: whether this function can sleep
+ * @gtp_flags: kvm_gtp_flag_t flags (atomic, write, ..)
   * @async: whether this function need to wait IO complete if the
   *         host page is not in the memory
- * @write_fault: whether we should get a writable host page
   * @writable: whether it allows to map a writable host page for !@write_fault
   *
- * The function will map a writable host page for these two cases:
+ * The function will map a writable (KVM_GTP_WRITE set) host page for these
+ * two cases:
   * 1): @write_fault = true
   * 2): @write_fault = false && @writable, @writable will tell the caller
   *     whether the mapping is writable.
   */
-kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
-		     bool write_fault, bool *writable)
+kvm_pfn_t hva_to_pfn(unsigned long addr, kvm_gtp_flag_t gtp_flags, bool *async,
+		     bool *writable)
  {
+	bool write_fault = gtp_flags & KVM_GTP_WRITE;
+	bool atomic = gtp_flags & KVM_GTP_ATOMIC;
  	struct vm_area_struct *vma;
  	kvm_pfn_t pfn = 0;
  	int npages, r;
@@ -2592,7 +2596,7 @@ kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
  	if (atomic)
  		return KVM_PFN_ERR_FAULT;
- npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
+	npages = hva_to_pfn_slow(addr, async, gtp_flags, writable, &pfn);
  	if (npages == 1)
  		return pfn;
@@ -2625,10 +2629,11 @@ kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
  }
kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
-			       bool atomic, bool *async, bool write_fault,
+			       kvm_gtp_flag_t gtp_flags, bool *async,
  			       bool *writable, hva_t *hva)
  {
-	unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);
+	unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL,
+					       gtp_flags & KVM_GTP_WRITE);
if (hva)
  		*hva = addr;
@@ -2651,28 +2656,30 @@ kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
  		writable = NULL;
  	}
- return hva_to_pfn(addr, atomic, async, write_fault,
-			  writable);
+	return hva_to_pfn(addr, gtp_flags, async, writable);
  }
  EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);
kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
  		      bool *writable)
  {
-	return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
-				    write_fault, writable, NULL);
+	return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn,
+				    write_fault ? KVM_GTP_WRITE : 0,
+				    NULL, writable, NULL);
  }
  EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);
kvm_pfn_t gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
  {
-	return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL, NULL);
+	return __gfn_to_pfn_memslot(slot, gfn, KVM_GTP_WRITE,
+				    NULL, NULL, NULL);
  }
  EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);
kvm_pfn_t gfn_to_pfn_memslot_atomic(const struct kvm_memory_slot *slot, gfn_t gfn)
  {
-	return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL, NULL);
+	return __gfn_to_pfn_memslot(slot, gfn, KVM_GTP_WRITE | KVM_GTP_ATOMIC,
+				    NULL, NULL, NULL);
  }
  EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);
diff --git a/virt/kvm/kvm_mm.h b/virt/kvm/kvm_mm.h
index 41da467d99c9..1c870911eb48 100644
--- a/virt/kvm/kvm_mm.h
+++ b/virt/kvm/kvm_mm.h
@@ -3,6 +3,8 @@
  #ifndef __KVM_MM_H__
  #define __KVM_MM_H__ 1
+#include <linux/kvm_host.h>
+
  /*
   * Architectures can choose whether to use an rwlock or spinlock
   * for the mmu_lock.  These macros, for use in common code
@@ -24,8 +26,8 @@
  #define KVM_MMU_READ_UNLOCK(kvm)	spin_unlock(&(kvm)->mmu_lock)
  #endif /* KVM_HAVE_MMU_RWLOCK */
-kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
-		     bool write_fault, bool *writable);
+kvm_pfn_t hva_to_pfn(unsigned long addr, kvm_gtp_flag_t gtp_flags, bool *async,
+		     bool *writable);
#ifdef CONFIG_HAVE_KVM_PFNCACHE
  void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm,
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index dd84676615f1..0f9f6b5d2fbb 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -123,7 +123,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct kvm *kvm, unsigned long uhva)
  		smp_rmb();
/* We always request a writeable mapping */
-		new_pfn = hva_to_pfn(uhva, false, NULL, true, NULL);
+		new_pfn = hva_to_pfn(uhva, KVM_GTP_WRITE, NULL, NULL);
  		if (is_error_noslot_pfn(new_pfn))
  			break;




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