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Subject[RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface
Date
__flush_tlb_one_user() currently flushes a single entry, and flushes it
both in the kernel and user page-tables, when PTI is enabled.

Change __flush_tlb_one_user() and related interfaces into
__flush_tlb_range() that flushes a range and does not flush the user
page-table.

This refactoring is needed for the next patch, but regardless makes
sense and has several advantages. First, only Xen-PV, which does not
use PTI, implements the paravirtual interface of flush_tlb_one_user() so
nothing is broken by separating the user and kernel page-table flushes,
and the interface is more intuitive.

Second, INVLPG can flush unrelated mappings, and it is also a
serializing instruction. It is better to have a tight loop that flushes
the entries.

Third, currently __flush_tlb_one_kernel() also flushes the user
page-tables, which is not needed. This allows to avoid this redundant
flush.

Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Nadav Amit <namit@vmware.com>
---
arch/x86/include/asm/paravirt.h | 5 ++--
arch/x86/include/asm/paravirt_types.h | 3 ++-
arch/x86/include/asm/tlbflush.h | 24 +++++------------
arch/x86/kernel/paravirt.c | 7 ++---
arch/x86/mm/tlb.c | 39 ++++++++++++++++++++++-----
arch/x86/xen/mmu_pv.c | 21 +++++++++------
6 files changed, 62 insertions(+), 37 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index bc4829c9b3f9..7347328eacd3 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -57,9 +57,10 @@ static inline void __flush_tlb_global(void)
PVOP_VCALL0(mmu.flush_tlb_kernel);
}

-static inline void __flush_tlb_one_user(unsigned long addr)
+static inline void __flush_tlb_range(unsigned long start, unsigned long end,
+ u8 stride_shift)
{
- PVOP_VCALL1(mmu.flush_tlb_one_user, addr);
+ PVOP_VCALL3(mmu.flush_tlb_range, start, end, stride_shift);
}

static inline void flush_tlb_multi(const struct cpumask *cpumask,
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 63fa751344bf..a87a5f236251 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -205,7 +205,8 @@ struct pv_mmu_ops {
/* TLB operations */
void (*flush_tlb_user)(void);
void (*flush_tlb_kernel)(void);
- void (*flush_tlb_one_user)(unsigned long addr);
+ void (*flush_tlb_range)(unsigned long start, unsigned long end,
+ u8 stride_shift);
void (*flush_tlb_multi)(const struct cpumask *cpus,
const struct flush_tlb_info *info);

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 1f88ea410ff3..421bc82504e2 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -145,7 +145,7 @@ static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
#else
#define __flush_tlb() __native_flush_tlb()
#define __flush_tlb_global() __native_flush_tlb_global()
-#define __flush_tlb_one_user(addr) __native_flush_tlb_one_user(addr)
+#define __flush_tlb_range(start, end, stride_shift) __native_flush_tlb_range(start, end, stride_shift)
#endif

struct tlb_context {
@@ -454,23 +454,13 @@ static inline void __native_flush_tlb_global(void)
/*
* flush one page in the user mapping
*/
-static inline void __native_flush_tlb_one_user(unsigned long addr)
+static inline void __native_flush_tlb_range(unsigned long start,
+ unsigned long end, u8 stride_shift)
{
- u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+ unsigned long addr;

- asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
-
- if (!static_cpu_has(X86_FEATURE_PTI))
- return;
-
- /*
- * Some platforms #GP if we call invpcid(type=1/2) before CR4.PCIDE=1.
- * Just use invalidate_user_asid() in case we are called early.
- */
- if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE))
- invalidate_user_asid(loaded_mm_asid);
- else
- invpcid_flush_one(user_pcid(loaded_mm_asid), addr);
+ for (addr = start; addr < end; addr += 1ul << stride_shift)
+ asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
}

/*
@@ -512,7 +502,7 @@ static inline void __flush_tlb_one_kernel(unsigned long addr)
* kernel address space and for its usermode counterpart, but it does
* not flush it for other address spaces.
*/
- __flush_tlb_one_user(addr);
+ __flush_tlb_range(addr, addr + PAGE_SIZE, PAGE_SHIFT);

if (!static_cpu_has(X86_FEATURE_PTI))
return;
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 5520a04c84ba..195f5577d0d5 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -173,9 +173,10 @@ static void native_flush_tlb_global(void)
__native_flush_tlb_global();
}

-static void native_flush_tlb_one_user(unsigned long addr)
+static void native_flush_tlb_range(unsigned long start, unsigned long end,
+ u8 stride_shift)
{
- __native_flush_tlb_one_user(addr);
+ __native_flush_tlb_range(start, end, stride_shift);
}

struct static_key paravirt_steal_enabled;
@@ -358,7 +359,7 @@ struct paravirt_patch_template pv_ops = {
/* Mmu ops. */
.mmu.flush_tlb_user = native_flush_tlb,
.mmu.flush_tlb_kernel = native_flush_tlb_global,
- .mmu.flush_tlb_one_user = native_flush_tlb_one_user,
+ .mmu.flush_tlb_range = native_flush_tlb_range,
.mmu.flush_tlb_multi = native_flush_tlb_multi,
.mmu.tlb_remove_table =
(void (*)(struct mmu_gather *, void *))tlb_remove_page,
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 0addc6e84126..ad15fc2c0790 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -512,6 +512,35 @@ void initialize_tlbstate_and_flush(void)
this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
}

+static void flush_tlb_user_pt_range(u16 asid, const struct flush_tlb_info *f)
+{
+ unsigned long start, end, addr;
+ u8 stride_shift;
+
+ if (!static_cpu_has(X86_FEATURE_PTI))
+ return;
+
+ /*
+ * Read the data into variable on the stack to prevent it from being
+ * reevaluated due to invpcid memory clobber.
+ */
+ start = f->start;
+ end = f->end;
+ stride_shift = f->stride_shift;
+
+ /*
+ * Some platforms #GP if we call invpcid(type=1/2) before CR4.PCIDE=1.
+ * Just use invalidate_user_asid() in case we are called early.
+ */
+ if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)) {
+ invalidate_user_asid(asid);
+ return;
+ }
+
+ for (addr = start; addr < end; addr += 1ul << stride_shift)
+ invpcid_flush_one(user_pcid(asid), addr);
+}
+
/*
* flush_tlb_func()'s memory ordering requirement is that any
* TLB fills that happen after we flush the TLB are ordered after we
@@ -624,14 +653,12 @@ static void flush_tlb_func(void *info)
f->new_tlb_gen == local_tlb_gen + 1 &&
f->new_tlb_gen == mm_tlb_gen) {
/* Partial flush */
- unsigned long addr = f->start;
-
nr_invalidate = (f->end - f->start) >> f->stride_shift;

- while (addr < f->end) {
- __flush_tlb_one_user(addr);
- addr += 1UL << f->stride_shift;
- }
+ __flush_tlb_range(f->start, f->end, f->stride_shift);
+
+ flush_tlb_user_pt_range(loaded_mm_asid, f);
+
if (local)
count_vm_tlb_events(NR_TLB_LOCAL_FLUSH_ONE, nr_invalidate);
} else {
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 48f7c7eb4dbc..ed68657f5e77 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1325,22 +1325,27 @@ static noinline void xen_flush_tlb(void)
preempt_enable();
}

-static void xen_flush_tlb_one_user(unsigned long addr)
+static void xen_flush_tlb_range(unsigned long start, unsigned long end,
+ u8 stride_shift)
{
struct mmuext_op *op;
struct multicall_space mcs;
-
- trace_xen_mmu_flush_tlb_one_user(addr);
+ unsigned long addr;

preempt_disable();

mcs = xen_mc_entry(sizeof(*op));
op = mcs.args;
- op->cmd = MMUEXT_INVLPG_LOCAL;
- op->arg1.linear_addr = addr & PAGE_MASK;
- MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);

- xen_mc_issue(PARAVIRT_LAZY_MMU);
+ for (addr = start; addr < end; addr += 1ul << stride_shift) {
+ trace_xen_mmu_flush_tlb_one_user(addr);
+
+ op->cmd = MMUEXT_INVLPG_LOCAL;
+ op->arg1.linear_addr = addr & PAGE_MASK;
+ MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
+
+ xen_mc_issue(PARAVIRT_LAZY_MMU);
+ }

preempt_enable();
}
@@ -2394,7 +2399,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {

.flush_tlb_user = xen_flush_tlb,
.flush_tlb_kernel = xen_flush_tlb,
- .flush_tlb_one_user = xen_flush_tlb_one_user,
+ .flush_tlb_range = xen_flush_tlb_range,
.flush_tlb_multi = xen_flush_tlb_multi,
.tlb_remove_table = tlb_remove_table,

--
2.17.1
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