All of lore.kernel.org
 help / color / mirror / Atom feed
From: Roger Pau Monne <roger.pau@citrix.com>
To: <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
	Jan Beulich <jbeulich@suse.com>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: [Xen-devel] [PATCH v2 3/3] x86/tlb: use Xen L0 assisted TLB flush when available
Date: Fri, 10 Jan 2020 17:04:04 +0100	[thread overview]
Message-ID: <20200110160404.15573-4-roger.pau@citrix.com> (raw)
In-Reply-To: <20200110160404.15573-1-roger.pau@citrix.com>

Use Xen's L0 HVMOP_flush_tlbs hypercall in order to perform flushes.
This greatly increases the performance of TLB flushes when running
with a high amount of vCPUs as a Xen guest, and is specially important
when running in shim mode.

The following figures are from a PV guest running `make -j32 xen` in
shim mode with 32 vCPUs.

Using x2APIC and ALLBUT shorthand:
real	4m35.973s
user	4m35.110s
sys	36m24.117s

Using L0 assisted flush:
real    1m14.206s
user    4m31.835s
sys     5m45.013s

The implementation adds a new hook to hypervisor_ops so other
enlightenments can also implement such assisted flush just by filling
the hook. Note that the Xen implementation completely ignores the
dirty CPU mask and the linear address passed in, and always performs a
global TLB flush on all vCPUs.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v1:
 - Add a L0 assisted hook to hypervisor ops.
---
 xen/arch/x86/guest/hypervisor.c        |  9 +++++++++
 xen/arch/x86/guest/xen/xen.c           |  6 ++++++
 xen/arch/x86/smp.c                     |  6 ++++++
 xen/include/asm-x86/guest/hypervisor.h | 13 +++++++++++++
 4 files changed, 34 insertions(+)

diff --git a/xen/arch/x86/guest/hypervisor.c b/xen/arch/x86/guest/hypervisor.c
index 4f27b98740..c793ba51c2 100644
--- a/xen/arch/x86/guest/hypervisor.c
+++ b/xen/arch/x86/guest/hypervisor.c
@@ -18,6 +18,7 @@
  *
  * Copyright (c) 2019 Microsoft.
  */
+#include <xen/cpumask.h>
 #include <xen/init.h>
 #include <xen/types.h>
 
@@ -64,6 +65,14 @@ void hypervisor_resume(void)
         ops->resume();
 }
 
+int hypervisor_flush_tlb(const cpumask_t *mask, const void *va)
+{
+    if ( ops && ops->flush_tlb )
+        return ops->flush_tlb(mask, va);
+
+    return -ENOSYS;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/arch/x86/guest/xen/xen.c b/xen/arch/x86/guest/xen/xen.c
index 6dbc5f953f..47af773aca 100644
--- a/xen/arch/x86/guest/xen/xen.c
+++ b/xen/arch/x86/guest/xen/xen.c
@@ -310,11 +310,17 @@ static void resume(void)
         pv_console_init();
 }
 
+static int flush_tlb(const cpumask_t *mask, const void *va)
+{
+    return xen_hypercall_hvm_op(HVMOP_flush_tlbs, NULL);
+}
+
 static const struct hypervisor_ops ops = {
     .name = "Xen",
     .setup = setup,
     .ap_setup = ap_setup,
     .resume = resume,
+    .flush_tlb = flush_tlb,
 };
 
 const struct hypervisor_ops *__init xg_probe(void)
diff --git a/xen/arch/x86/smp.c b/xen/arch/x86/smp.c
index 6510dd84ab..b3cb1ba90f 100644
--- a/xen/arch/x86/smp.c
+++ b/xen/arch/x86/smp.c
@@ -15,6 +15,7 @@
 #include <xen/perfc.h>
 #include <xen/spinlock.h>
 #include <asm/current.h>
+#include <asm/guest.h>
 #include <asm/smp.h>
 #include <asm/mc146818rtc.h>
 #include <asm/flushtlb.h>
@@ -262,6 +263,11 @@ void flush_area_mask(const cpumask_t *mask, const void *va, unsigned int flags)
     if ( (flags & ~FLUSH_ORDER_MASK) &&
          !cpumask_subset(mask, cpumask_of(cpu)) )
     {
+        if ( cpu_has_hypervisor &&
+             !(flags & ~(FLUSH_TLB | FLUSH_TLB_GLOBAL | FLUSH_VA_VALID)) &&
+             !hypervisor_flush_tlb(mask, va) )
+            return;
+
         spin_lock(&flush_lock);
         cpumask_and(&flush_cpumask, mask, &cpu_online_map);
         cpumask_clear_cpu(cpu, &flush_cpumask);
diff --git a/xen/include/asm-x86/guest/hypervisor.h b/xen/include/asm-x86/guest/hypervisor.h
index 392f4b90ae..b7f1969796 100644
--- a/xen/include/asm-x86/guest/hypervisor.h
+++ b/xen/include/asm-x86/guest/hypervisor.h
@@ -28,6 +28,8 @@ struct hypervisor_ops {
     void (*ap_setup)(void);
     /* Resume from suspension */
     void (*resume)(void);
+    /* L0 assisted TLB flush */
+    int (*flush_tlb)(const cpumask_t *mask, const void *va);
 };
 
 #ifdef CONFIG_GUEST
@@ -36,9 +38,16 @@ const char *hypervisor_probe(void);
 void hypervisor_setup(void);
 void hypervisor_ap_setup(void);
 void hypervisor_resume(void);
+/*
+ * L0 assisted TLB flush.
+ * mask: cpumask of the dirty vCPUs that should be flushed.
+ * va: linear address to flush, or NULL for global flushes.
+ */
+int hypervisor_flush_tlb(const cpumask_t *mask, const void *va);
 
 #else
 
+#include <xen/cpumask.h>
 #include <xen/lib.h>
 #include <xen/types.h>
 
@@ -46,6 +55,10 @@ static inline const char *hypervisor_probe(void) { return NULL; }
 static inline void hypervisor_setup(void) { ASSERT_UNREACHABLE(); }
 static inline void hypervisor_ap_setup(void) { ASSERT_UNREACHABLE(); }
 static inline void hypervisor_resume(void) { ASSERT_UNREACHABLE(); }
+static inline int hypervisor_flush_tlb(const cpumask_t *mask, const void *va)
+{
+    return -ENOSYS;
+}
 
 #endif  /* CONFIG_GUEST */
 
-- 
2.24.1


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  parent reply	other threads:[~2020-01-10 16:04 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 16:04 [Xen-devel] [PATCH v2 0/3] x86: improve assisted tlb flush and use it in guest mode Roger Pau Monne
2020-01-10 16:04 ` [Xen-devel] [PATCH v2 1/3] x86/hvm: allow ASID flush when v != current Roger Pau Monne
2020-01-10 16:04 ` [Xen-devel] [PATCH v2 2/3] x86/hvm: rework HVMOP_flush_tlbs Roger Pau Monne
2020-01-10 16:04 ` Roger Pau Monne [this message]
2020-01-10 16:08 ` [Xen-devel] [PATCH v2 0/3] x86: improve assisted tlb flush and use it in guest mode Jan Beulich
2020-01-10 16:14   ` Roger Pau Monné

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200110160404.15573-4-roger.pau@citrix.com \
    --to=roger.pau@citrix.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=jbeulich@suse.com \
    --cc=wl@xen.org \
    --cc=xen-devel@lists.xenproject.org \
    --subject='Re: [Xen-devel] [PATCH v2 3/3] x86/tlb: use Xen L0 assisted TLB flush when available' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.