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Message-Id: <20200206030900.147032-9-leonardo@linux.ibm.com>
Date: Thu, 6 Feb 2020 00:08:57 -0300
From: Leonardo Bras <leonardo@...ux.ibm.com>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Arnd Bergmann <arnd@...db.de>,
Andrew Morton <akpm@...ux-foundation.org>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@....fr>,
Steven Price <steven.price@....com>,
Robin Murphy <robin.murphy@....com>,
Leonardo Bras <leonardo@...ux.ibm.com>,
Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
Balbir Singh <bsingharora@...il.com>,
Reza Arbab <arbab@...ux.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Allison Randal <allison@...utok.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mike Rapoport <rppt@...ux.ibm.com>,
Michal Suchanek <msuchanek@...e.de>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
kvm-ppc@...r.kernel.org, linux-arch@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH v6 08/11] powerpc/kvm/book3s_hv: Use functions to track lockless pgtbl walks
Applies the new functions for tracking all book3s_hv related
functions that do lockless pagetable walks.
Adds comments explaining that some lockless pagetable walks don't need
protection due to guest pgd not being a target of THP collapse/split, or
due to being called from Realmode + MSR_EE = 0
kvmppc_do_h_enter: Fixes where local_irq_restore() must be placed (after
the last usage of ptep).
Given that some of these functions can be called in real mode, and others
always are, we use __{begin,end}_lockless_pgtbl_walk so we can decide when
to disable interrupts.
Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>
---
arch/powerpc/kvm/book3s_hv_nested.c | 22 ++++++++++++++++++++--
arch/powerpc/kvm/book3s_hv_rm_mmu.c | 28 ++++++++++++++++++----------
2 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index dc97e5be76f6..a398061d5778 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -803,7 +803,11 @@ static void kvmhv_update_nest_rmap_rc(struct kvm *kvm, u64 n_rmap,
if (!gp)
return;
- /* Find the pte */
+ /* Find the pte:
+ * We are walking the nested guest (partition-scoped) page table here.
+ * We can do this without disabling irq because the Linux MM
+ * subsystem doesn't do THP splits and collapses on this tree.
+ */
ptep = __find_linux_pte(gp->shadow_pgtable, gpa, NULL, &shift);
/*
* If the pte is present and the pfn is still the same, update the pte.
@@ -853,7 +857,11 @@ static void kvmhv_remove_nest_rmap(struct kvm *kvm, u64 n_rmap,
if (!gp)
return;
- /* Find and invalidate the pte */
+ /* Find and invalidate the pte:
+ * We are walking the nested guest (partition-scoped) page table here.
+ * We can do this without disabling irq because the Linux MM
+ * subsystem doesn't do THP splits and collapses on this tree.
+ */
ptep = __find_linux_pte(gp->shadow_pgtable, gpa, NULL, &shift);
/* Don't spuriously invalidate ptes if the pfn has changed */
if (ptep && pte_present(*ptep) && ((pte_val(*ptep) & mask) == hpa))
@@ -921,6 +929,11 @@ static bool kvmhv_invalidate_shadow_pte(struct kvm_vcpu *vcpu,
int shift;
spin_lock(&kvm->mmu_lock);
+ /*
+ * We are walking the nested guest (partition-scoped) page table here.
+ * We can do this without disabling irq because the Linux MM
+ * subsystem doesn't do THP splits and collapses on this tree.
+ */
ptep = __find_linux_pte(gp->shadow_pgtable, gpa, NULL, &shift);
if (!shift)
shift = PAGE_SHIFT;
@@ -1362,6 +1375,11 @@ static long int __kvmhv_nested_page_fault(struct kvm_run *run,
/* See if can find translation in our partition scoped tables for L1 */
pte = __pte(0);
spin_lock(&kvm->mmu_lock);
+ /*
+ * We are walking the secondary (partition-scoped) page table here.
+ * We can do this without disabling irq because the Linux MM
+ * subsystem doesn't do THP splits and collapses on this tree.
+ */
pte_p = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
if (!shift)
shift = PAGE_SHIFT;
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 220305454c23..fd4d8f174f09 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -210,7 +210,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
pte_t *ptep;
unsigned int writing;
unsigned long mmu_seq;
- unsigned long rcbits, irq_flags = 0;
+ unsigned long rcbits, irq_mask = 0;
if (kvm_is_radix(kvm))
return H_FUNCTION;
@@ -252,8 +252,8 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
* If we had a page table table change after lookup, we would
* retry via mmu_notifier_retry.
*/
- if (!realmode)
- local_irq_save(irq_flags);
+ irq_mask = __begin_lockless_pgtbl_walk(!realmode);
+
/*
* If called in real mode we have MSR_EE = 0. Otherwise
* we disable irq above.
@@ -272,8 +272,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
* to <= host page size, if host is using hugepage
*/
if (host_pte_size < psize) {
- if (!realmode)
- local_irq_restore(flags);
+ __end_lockless_pgtbl_walk(irq_mask, !realmode);
return H_PARAMETER;
}
pte = kvmppc_read_update_linux_pte(ptep, writing);
@@ -287,8 +286,6 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
pa |= gpa & ~PAGE_MASK;
}
}
- if (!realmode)
- local_irq_restore(irq_flags);
ptel &= HPTE_R_KEY | HPTE_R_PP0 | (psize-1);
ptel |= pa;
@@ -302,8 +299,10 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
/*If we had host pte mapping then Check WIMG */
if (ptep && !hpte_cache_flags_ok(ptel, is_ci)) {
- if (is_ci)
+ if (is_ci) {
+ __end_lockless_pgtbl_walk(irq_mask, !realmode);
return H_PARAMETER;
+ }
/*
* Allow guest to map emulated device memory as
* uncacheable, but actually make it cacheable.
@@ -311,6 +310,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
ptel &= ~(HPTE_R_W|HPTE_R_I|HPTE_R_G);
ptel |= HPTE_R_M;
}
+ __end_lockless_pgtbl_walk(irq_mask, !realmode);
/* Find and lock the HPTEG slot to use */
do_insert:
@@ -907,11 +907,19 @@ static int kvmppc_get_hpa(struct kvm_vcpu *vcpu, unsigned long gpa,
/* Translate to host virtual address */
hva = __gfn_to_hva_memslot(memslot, gfn);
- /* Try to find the host pte for that virtual address */
+ /* Try to find the host pte for that virtual address :
+ * Called by hcall_real_table (real mode + MSR_EE=0)
+ * Interrupts are disabled here.
+ */
+ __begin_lockless_pgtbl_walk(false);
ptep = __find_linux_pte(vcpu->arch.pgdir, hva, NULL, &shift);
- if (!ptep)
+ if (!ptep) {
+ __end_lockless_pgtbl_walk(0, false);
return H_TOO_HARD;
+ }
pte = kvmppc_read_update_linux_pte(ptep, writing);
+ __end_lockless_pgtbl_walk(0, false);
+
if (!pte_present(pte))
return H_TOO_HARD;
--
2.24.1
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