[Xen-devel] [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface

[Xen-devel] [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface

[Nadav Amit]

__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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Re: [Xen-devel] [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface

[Juergen Gross]

On 24.08.19 00:52, Nadav Amit wrote:
> __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/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);
> +	}

For this kind of usage (a loop) you should:

- replace the call of xen_mc_entry() with xen_mc_batch()
- use xen_extend_mmuext_op() for each loop iteration
- call xen_mc_issue() after the loop

Additionally I'd like you to replace trace_xen_mmu_flush_tlb_one_user()
with trace_xen_mmu_flush_tlb_range() taking all three parameters and
keep it where it was (out of the loop).

The paravirt parts seem to be okay.


Juergen

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Re: [Xen-devel] [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface

[Nadav Amit]

> On Aug 26, 2019, at 12:51 AM, Juergen Gross <jgross@suse.com> wrote:
> 
> On 24.08.19 00:52, Nadav Amit wrote:
>> __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/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);
>> +	}
> 
> For this kind of usage (a loop) you should:
> 
> - replace the call of xen_mc_entry() with xen_mc_batch()
> - use xen_extend_mmuext_op() for each loop iteration
> - call xen_mc_issue() after the loop
> 
> Additionally I'd like you to replace trace_xen_mmu_flush_tlb_one_user()
> with trace_xen_mmu_flush_tlb_range() taking all three parameters and
> keep it where it was (out of the loop).
> 
> The paravirt parts seem to be okay.

Thanks for the quick response. I don’t think the preempt_disable/enable() is
needed in this case, but I kept them. Does the following match what you had
in mind?

---
 arch/x86/xen/mmu_pv.c      | 25 ++++++++++++++-----------
 include/trace/events/xen.h | 18 ++++++++++++------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 48f7c7eb4dbc..faa01591df36 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1325,20 +1325,23 @@ 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);
+	struct mmuext_op op;
+	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_batch();
+	op.cmd = MMUEXT_INVLPG_LOCAL;
+
+	trace_xen_mmu_flush_tlb_range(start, end, stride_shift);
+
+	for (addr = start; addr < end; addr += 1ul << stride_shift) {
+		op.arg1.linear_addr = addr & PAGE_MASK;
+		xen_extend_mmuext_op(&op);
+	}
 
 	xen_mc_issue(PARAVIRT_LAZY_MMU);
 
@@ -2394,7 +2397,7 @@ 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,
 
diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
index 546022acf160..32bf0a94b4d8 100644
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -352,14 +352,20 @@ DECLARE_EVENT_CLASS(xen_mmu_pgd,
 DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_pin);
 DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_unpin);
 
-TRACE_EVENT(xen_mmu_flush_tlb_one_user,
-	    TP_PROTO(unsigned long addr),
-	    TP_ARGS(addr),
+TRACE_EVENT(xen_mmu_flush_tlb_range,
+	    TP_PROTO(unsigned long start, unsigned long end,
+		     unsigned char stride_shift),
+	    TP_ARGS(start, end, stride_shift),
 	    TP_STRUCT__entry(
-		    __field(unsigned long, addr)
+		    __field(unsigned long, start)
+		    __field(unsigned long, end)
+		    __field(unsigned char, stride_shift)
 		    ),
-	    TP_fast_assign(__entry->addr = addr),
-	    TP_printk("addr %lx", __entry->addr)
+	    TP_fast_assign(__entry->start = start;
+			   __entry->end = end;
+			   __entry->stride_shift = stride_shift),
+	    TP_printk("start %lx end %lx stride_shift %d", __entry->start,
+		      __entry->end, __entry->stride_shift)
 	);
 
 TRACE_EVENT(xen_mmu_flush_tlb_multi,
-- 
2.17.1

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Re: [Xen-devel] [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface

[Juergen Gross]

On 26.08.19 18:38, Nadav Amit wrote:
>> On Aug 26, 2019, at 12:51 AM, Juergen Gross <jgross@suse.com> wrote:
>>
>> On 24.08.19 00:52, Nadav Amit wrote:
>>> __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/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);
>>> +	}
>>
>> For this kind of usage (a loop) you should:
>>
>> - replace the call of xen_mc_entry() with xen_mc_batch()
>> - use xen_extend_mmuext_op() for each loop iteration
>> - call xen_mc_issue() after the loop
>>
>> Additionally I'd like you to replace trace_xen_mmu_flush_tlb_one_user()
>> with trace_xen_mmu_flush_tlb_range() taking all three parameters and
>> keep it where it was (out of the loop).
>>
>> The paravirt parts seem to be okay.
> 
> Thanks for the quick response. I don’t think the preempt_disable/enable() is
> needed in this case, but I kept them. Does the following match what you had
> in mind?

Yes, it does.

BTW, preempt_disable/enable() is needed as xen_mc_batch() ...
xen_mc_issue() is using a percpu buffer.


Juergen

> 
> ---
>   arch/x86/xen/mmu_pv.c      | 25 ++++++++++++++-----------
>   include/trace/events/xen.h | 18 ++++++++++++------
>   2 files changed, 26 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 48f7c7eb4dbc..faa01591df36 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -1325,20 +1325,23 @@ 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);
> +	struct mmuext_op op;
> +	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_batch();
> +	op.cmd = MMUEXT_INVLPG_LOCAL;
> +
> +	trace_xen_mmu_flush_tlb_range(start, end, stride_shift);
> +
> +	for (addr = start; addr < end; addr += 1ul << stride_shift) {
> +		op.arg1.linear_addr = addr & PAGE_MASK;
> +		xen_extend_mmuext_op(&op);
> +	}
>   
>   	xen_mc_issue(PARAVIRT_LAZY_MMU);
>   
> @@ -2394,7 +2397,7 @@ 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,
>   
> diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
> index 546022acf160..32bf0a94b4d8 100644
> --- a/include/trace/events/xen.h
> +++ b/include/trace/events/xen.h
> @@ -352,14 +352,20 @@ DECLARE_EVENT_CLASS(xen_mmu_pgd,
>   DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_pin);
>   DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_unpin);
>   
> -TRACE_EVENT(xen_mmu_flush_tlb_one_user,
> -	    TP_PROTO(unsigned long addr),
> -	    TP_ARGS(addr),
> +TRACE_EVENT(xen_mmu_flush_tlb_range,
> +	    TP_PROTO(unsigned long start, unsigned long end,
> +		     unsigned char stride_shift),
> +	    TP_ARGS(start, end, stride_shift),
>   	    TP_STRUCT__entry(
> -		    __field(unsigned long, addr)
> +		    __field(unsigned long, start)
> +		    __field(unsigned long, end)
> +		    __field(unsigned char, stride_shift)
>   		    ),
> -	    TP_fast_assign(__entry->addr = addr),
> -	    TP_printk("addr %lx", __entry->addr)
> +	    TP_fast_assign(__entry->start = start;
> +			   __entry->end = end;
> +			   __entry->stride_shift = stride_shift),
> +	    TP_printk("start %lx end %lx stride_shift %d", __entry->start,
> +		      __entry->end, __entry->stride_shift)
>   	);
>   
>   TRACE_EVENT(xen_mmu_flush_tlb_multi,
> 


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