Re: [PATCH kernel v3 7/7] KVM: PPC: Add support for multiple-TCE hcalls

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On 02/15/2016 12:55 PM, Alexey Kardashevskiy wrote:
This adds real and virtual mode handlers for the H_PUT_TCE_INDIRECT and
H_STUFF_TCE hypercalls for user space emulated devices such as IBMVIO
devices or emulated PCI. These calls allow adding multiple entries
(up to 512) into the TCE table in one call which saves time on
transition between kernel and user space.

The current implementation of kvmppc_h_stuff_tce() allows it to be
executed in both real and virtual modes so there is one helper.
The kvmppc_rm_h_put_tce_indirect() needs to translate the guest address
to the host address and since the translation is different, there are
2 helpers - one for each mode.

This implements the KVM_CAP_PPC_MULTITCE capability. When present,
the kernel will try handling H_PUT_TCE_INDIRECT and H_STUFF_TCE if these
are enabled by the userspace via KVM_CAP_PPC_ENABLE_HCALL.
If they can not be handled by the kernel, they are passed on to
the user space. The user space still has to have an implementation
for these.

Both HV and PR-syle KVM are supported.

Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
---
[skip]

diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
index b608fdd..0486aa2 100644
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -14,6 +14,7 @@
   *
   * Copyright 2010 Paul Mackerras, IBM Corp. <paulus@xxxxxxxxxxx>
   * Copyright 2011 David Gibson, IBM Corporation <dwg@xxxxxxxxxxx>
+ * Copyright 2016 Alexey Kardashevskiy, IBM Corporation <aik@xxxxxxxxxxx>
   */

  #include <linux/types.h>
@@ -30,6 +31,7 @@
  #include <asm/kvm_ppc.h>
  #include <asm/kvm_book3s.h>
  #include <asm/mmu-hash64.h>
+#include <asm/mmu_context.h>
  #include <asm/hvcall.h>
  #include <asm/synch.h>
  #include <asm/ppc-opcode.h>
@@ -37,6 +39,7 @@
  #include <asm/udbg.h>
  #include <asm/iommu.h>
  #include <asm/tce.h>
+#include <asm/iommu.h>

  #define TCES_PER_PAGE	(PAGE_SIZE / sizeof(u64))

@@ -46,7 +49,7 @@
   * WARNING: This will be called in real or virtual mode on HV KVM and virtual
   *          mode on PR KVM
   */
-static struct kvmppc_spapr_tce_table *kvmppc_find_table(struct kvm_vcpu *vcpu,
+struct kvmppc_spapr_tce_table *kvmppc_find_table(struct kvm_vcpu *vcpu,
  		unsigned long liobn)
  {
  	struct kvm *kvm = vcpu->kvm;
@@ -58,6 +61,7 @@ static struct kvmppc_spapr_tce_table *kvmppc_find_table(struct kvm_vcpu *vcpu,

  	return NULL;
  }
+EXPORT_SYMBOL_GPL(kvmppc_find_table);

  /*
   * Validates IO address.
@@ -151,9 +155,29 @@ void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt,
  }
  EXPORT_SYMBOL_GPL(kvmppc_tce_put);

-/* WARNING: This will be called in real-mode on HV KVM and virtual
- *          mode on PR KVM
- */
+long kvmppc_gpa_to_ua(struct kvm *kvm, unsigned long gpa,
+		unsigned long *ua, unsigned long **prmap)
+{
+	unsigned long gfn = gpa >> PAGE_SHIFT;
+	struct kvm_memory_slot *memslot;
+
+	memslot = search_memslots(kvm_memslots(kvm), gfn);
+	if (!memslot)
+		return -EINVAL;
+
+	*ua = __gfn_to_hva_memslot(memslot, gfn) |
+		(gpa & ~(PAGE_MASK | TCE_PCI_READ | TCE_PCI_WRITE));
+
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+	if (prmap)
+		*prmap = &memslot->arch.rmap[gfn - memslot->base_gfn];
+#endif
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvmppc_gpa_to_ua);
+
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
  long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
  		      unsigned long ioba, unsigned long tce)
  {
@@ -180,6 +204,122 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
  }
  EXPORT_SYMBOL_GPL(kvmppc_h_put_tce);

+static long kvmppc_rm_ua_to_hpa(struct kvm_vcpu *vcpu,
+		unsigned long ua, unsigned long *phpa)
+{
+	pte_t *ptep, pte;
+	unsigned shift = 0;
+
+	ptep = __find_linux_pte_or_hugepte(vcpu->arch.pgdir, ua, NULL, &shift);



The latest powerkvm kernel passes @thp instead of NULL and check for it below in addition to (shift > PAGE_SHIFT), should it be fixed here as well?

Is that possible for __find_linux_pte_or_hugepte() return thp==true but shift<=PAGE_SHIT, assuming we call it on vcpu->arch.pgdir, not an ordinary task pgdir?



+	if (!ptep || !pte_present(*ptep))
+		return -ENXIO;
+	pte = *ptep;
+
+	if (!shift)
+		shift = PAGE_SHIFT;
+
+	/* Avoid handling anything potentially complicated in realmode */
+	if (shift > PAGE_SHIFT)
+		return -EAGAIN;
+
+	if (!pte_young(pte))
+		return -EAGAIN;
+
+	*phpa = (pte_pfn(pte) << PAGE_SHIFT) | (ua & ((1ULL << shift) - 1)) |
+			(ua & ~PAGE_MASK);
+
+	return 0;
+}


--
Alexey
--
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