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Subject[PATCH 19/36] KVM: ppc: support large host pages
Date
From: Hollis Blanchard <hollisb@us.ibm.com>

KVM on 440 has always been able to handle large guest mappings with 4K host
pages -- we must, since the guest kernel uses 256MB mappings.

This patch makes KVM work when the host has large pages too (tested with 64K).

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/powerpc/include/asm/kvm_ppc.h | 4 +-
arch/powerpc/kvm/44x_tlb.c | 71 ++++++++++++++++++++++++++++--------
arch/powerpc/kvm/booke.c | 12 ++++---
3 files changed, 64 insertions(+), 23 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 844f683..5bb2926 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -52,8 +52,8 @@ extern int kvmppc_emulate_instruction(struct kvm_run *run,
extern int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu);
extern void kvmppc_emulate_dec(struct kvm_vcpu *vcpu);

-extern void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn,
- u64 asid, u32 flags);
+extern void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gpa_t gpaddr,
+ u64 asid, u32 flags, u32 max_bytes);
extern void kvmppc_mmu_priv_switch(struct kvm_vcpu *vcpu, int usermode);
extern void kvmppc_mmu_switch_pid(struct kvm_vcpu *vcpu, u32 pid);

diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
index ee24618..d49dc66 100644
--- a/arch/powerpc/kvm/44x_tlb.c
+++ b/arch/powerpc/kvm/44x_tlb.c
@@ -28,6 +28,13 @@

#include "44x_tlb.h"

+#ifndef PPC44x_TLBE_SIZE
+#define PPC44x_TLBE_SIZE PPC44x_TLB_4K
+#endif
+
+#define PAGE_SIZE_4K (1<<12)
+#define PAGE_MASK_4K (~(PAGE_SIZE_4K - 1))
+
#define PPC44x_TLB_UATTR_MASK \
(PPC44x_TLB_U0|PPC44x_TLB_U1|PPC44x_TLB_U2|PPC44x_TLB_U3)
#define PPC44x_TLB_USER_PERM_MASK (PPC44x_TLB_UX|PPC44x_TLB_UR|PPC44x_TLB_UW)
@@ -179,15 +186,26 @@ void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
vcpu_44x->shadow_tlb_mod[i] = 1;
}

-/* Caller must ensure that the specified guest TLB entry is safe to insert into
- * the shadow TLB. */
-void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
- u32 flags)
+/**
+ * kvmppc_mmu_map -- create a host mapping for guest memory
+ *
+ * If the guest wanted a larger page than the host supports, only the first
+ * host page is mapped here and the rest are demand faulted.
+ *
+ * If the guest wanted a smaller page than the host page size, we map only the
+ * guest-size page (i.e. not a full host page mapping).
+ *
+ * Caller must ensure that the specified guest TLB entry is safe to insert into
+ * the shadow TLB.
+ */
+void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gpa_t gpaddr, u64 asid,
+ u32 flags, u32 max_bytes)
{
struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
struct page *new_page;
struct kvmppc_44x_tlbe *stlbe;
hpa_t hpaddr;
+ gfn_t gfn;
unsigned int victim;

/* Future optimization: don't overwrite the TLB entry containing the
@@ -198,6 +216,7 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
stlbe = &vcpu_44x->shadow_tlb[victim];

/* Get reference to new page. */
+ gfn = gpaddr >> PAGE_SHIFT;
new_page = gfn_to_page(vcpu->kvm, gfn);
if (is_error_page(new_page)) {
printk(KERN_ERR "Couldn't get guest page for gfn %lx!\n", gfn);
@@ -220,10 +239,25 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
stlbe->tid = !(asid & 0xff);

/* Force TS=1 for all guest mappings. */
- /* For now we hardcode 4KB mappings, but it will be important to
- * use host large pages in the future. */
- stlbe->word0 = (gvaddr & PAGE_MASK) | PPC44x_TLB_VALID | PPC44x_TLB_TS
- | PPC44x_TLB_4K;
+ stlbe->word0 = PPC44x_TLB_VALID | PPC44x_TLB_TS;
+
+ if (max_bytes >= PAGE_SIZE) {
+ /* Guest mapping is larger than or equal to host page size. We can use
+ * a "native" host mapping. */
+ stlbe->word0 |= (gvaddr & PAGE_MASK) | PPC44x_TLBE_SIZE;
+ } else {
+ /* Guest mapping is smaller than host page size. We must restrict the
+ * size of the mapping to be at most the smaller of the two, but for
+ * simplicity we fall back to a 4K mapping (this is probably what the
+ * guest is using anyways). */
+ stlbe->word0 |= (gvaddr & PAGE_MASK_4K) | PPC44x_TLB_4K;
+
+ /* 'hpaddr' is a host page, which is larger than the mapping we're
+ * inserting here. To compensate, we must add the in-page offset to the
+ * sub-page. */
+ hpaddr |= gpaddr & (PAGE_MASK ^ PAGE_MASK_4K);
+ }
+
stlbe->word1 = (hpaddr & 0xfffffc00) | ((hpaddr >> 32) & 0xf);
stlbe->word2 = kvmppc_44x_tlb_shadow_attrib(flags,
vcpu->arch.msr & MSR_PR);
@@ -322,10 +356,8 @@ static int tlbe_is_host_safe(const struct kvm_vcpu *vcpu,
int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
{
struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
- u64 eaddr;
- u64 raddr;
+ gva_t eaddr;
u64 asid;
- u32 flags;
struct kvmppc_44x_tlbe *tlbe;
unsigned int index;

@@ -364,15 +396,22 @@ int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
}

if (tlbe_is_host_safe(vcpu, tlbe)) {
+ gpa_t gpaddr;
+ u32 flags;
+ u32 bytes;
+
eaddr = get_tlb_eaddr(tlbe);
- raddr = get_tlb_raddr(tlbe);
+ gpaddr = get_tlb_raddr(tlbe);
+
+ /* Use the advertised page size to mask effective and real addrs. */
+ bytes = get_tlb_bytes(tlbe);
+ eaddr &= ~(bytes - 1);
+ gpaddr &= ~(bytes - 1);
+
asid = (tlbe->word0 & PPC44x_TLB_TS) | tlbe->tid;
flags = tlbe->word2 & 0xffff;

- /* Create a 4KB mapping on the host. If the guest wanted a
- * large page, only the first 4KB is mapped here and the rest
- * are mapped on the fly. */
- kvmppc_mmu_map(vcpu, eaddr, raddr >> PAGE_SHIFT, asid, flags);
+ kvmppc_mmu_map(vcpu, eaddr, gpaddr, asid, flags, bytes);
}

KVMTRACE_5D(GTLB_WRITE, vcpu, index,
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index ec59a67..924c7b4 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -308,8 +308,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
* b) the guest used a large mapping which we're faking
* Either way, we need to satisfy the fault without
* invoking the guest. */
- kvmppc_mmu_map(vcpu, eaddr, gfn, gtlbe->tid,
- gtlbe->word2);
+ kvmppc_mmu_map(vcpu, eaddr, vcpu->arch.paddr_accessed, gtlbe->tid,
+ gtlbe->word2, get_tlb_bytes(gtlbe));
vcpu->stat.dtlb_virt_miss_exits++;
r = RESUME_GUEST;
} else {
@@ -325,6 +325,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
case BOOKE_INTERRUPT_ITLB_MISS: {
struct kvmppc_44x_tlbe *gtlbe;
unsigned long eaddr = vcpu->arch.pc;
+ gpa_t gpaddr;
gfn_t gfn;

r = RESUME_GUEST;
@@ -340,7 +341,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,

vcpu->stat.itlb_virt_miss_exits++;

- gfn = tlb_xlate(gtlbe, eaddr) >> PAGE_SHIFT;
+ gpaddr = tlb_xlate(gtlbe, eaddr);
+ gfn = gpaddr >> PAGE_SHIFT;

if (kvm_is_visible_gfn(vcpu->kvm, gfn)) {
/* The guest TLB had a mapping, but the shadow TLB
@@ -349,8 +351,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
* b) the guest used a large mapping which we're faking
* Either way, we need to satisfy the fault without
* invoking the guest. */
- kvmppc_mmu_map(vcpu, eaddr, gfn, gtlbe->tid,
- gtlbe->word2);
+ kvmppc_mmu_map(vcpu, eaddr, gpaddr, gtlbe->tid,
+ gtlbe->word2, get_tlb_bytes(gtlbe));
} else {
/* Guest mapped and leaped at non-RAM! */
kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_MACHINE_CHECK);
--
1.6.0.3


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