KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 418 insertions, 0 deletions

diff --git a/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl b/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl
new file mode 100644
index 000000000..d16494c5e
--- /dev/null
+++ b/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl
@@ -0,0 +1,418 @@
+#!/usr/bin/env perl
+# This is a POC (proof of concept or piece of crap, take your pick) for reading the
+# text representation of trace output related to page allocation. It makes an attempt
+# to extract some high-level information on what is going on. The accuracy of the parser
+# may vary considerably
+#
+# Example usage: trace-pagealloc-postprocess.pl < /sys/kernel/tracing/trace_pipe
+# other options
+#   --prepend-parent	Report on the parent proc and PID
+#   --read-procstat	If the trace lacks process info, get it from /proc
+#   --ignore-pid	Aggregate processes of the same name together
+#
+# Copyright (c) IBM Corporation 2009
+# Author: Mel Gorman <mel@csn.ul.ie>
+use strict;
+use Getopt::Long;
+
+# Tracepoint events
+use constant MM_PAGE_ALLOC		=> 1;
+use constant MM_PAGE_FREE		=> 2;
+use constant MM_PAGE_FREE_BATCHED	=> 3;
+use constant MM_PAGE_PCPU_DRAIN		=> 4;
+use constant MM_PAGE_ALLOC_ZONE_LOCKED	=> 5;
+use constant MM_PAGE_ALLOC_EXTFRAG	=> 6;
+use constant EVENT_UNKNOWN		=> 7;
+
+# Constants used to track state
+use constant STATE_PCPU_PAGES_DRAINED	=> 8;
+use constant STATE_PCPU_PAGES_REFILLED	=> 9;
+
+# High-level events extrapolated from tracepoints
+use constant HIGH_PCPU_DRAINS		=> 10;
+use constant HIGH_PCPU_REFILLS		=> 11;
+use constant HIGH_EXT_FRAGMENT		=> 12;
+use constant HIGH_EXT_FRAGMENT_SEVERE	=> 13;
+use constant HIGH_EXT_FRAGMENT_MODERATE	=> 14;
+use constant HIGH_EXT_FRAGMENT_CHANGED	=> 15;
+
+my %perprocesspid;
+my %perprocess;
+my $opt_ignorepid;
+my $opt_read_procstat;
+my $opt_prepend_parent;
+
+# Catch sigint and exit on request
+my $sigint_report = 0;
+my $sigint_exit = 0;
+my $sigint_pending = 0;
+my $sigint_received = 0;
+sub sigint_handler {
+	my $current_time = time;
+	if ($current_time - 2 > $sigint_received) {
+		print "SIGINT received, report pending. Hit ctrl-c again to exit\n";
+		$sigint_report = 1;
+	} else {
+		if (!$sigint_exit) {
+			print "Second SIGINT received quickly, exiting\n";
+		}
+		$sigint_exit++;
+	}
+
+	if ($sigint_exit > 3) {
+		print "Many SIGINTs received, exiting now without report\n";
+		exit;
+	}
+
+	$sigint_received = $current_time;
+	$sigint_pending = 1;
+}
+$SIG{INT} = "sigint_handler";
+
+# Parse command line options
+GetOptions(
+	'ignore-pid'	 =>	\$opt_ignorepid,
+	'read-procstat'	 =>	\$opt_read_procstat,
+	'prepend-parent' =>	\$opt_prepend_parent,
+);
+
+# Defaults for dynamically discovered regex's
+my $regex_fragdetails_default = 'page=([0-9a-f]*) pfn=([0-9]*) alloc_order=([-0-9]*) fallback_order=([-0-9]*) pageblock_order=([-0-9]*) alloc_migratetype=([-0-9]*) fallback_migratetype=([-0-9]*) fragmenting=([-0-9]) change_ownership=([-0-9])';
+
+# Dyanically discovered regex
+my $regex_fragdetails;
+
+# Static regex used. Specified like this for readability and for use with /o
+#                      (process_pid)     (cpus      )   ( time  )   (tpoint    ) (details)
+my $regex_traceevent = '\s*([a-zA-Z0-9-]*)\s*(\[[0-9]*\])\s*([0-9.]*):\s*([a-zA-Z_]*):\s*(.*)';
+my $regex_statname = '[-0-9]*\s\((.*)\).*';
+my $regex_statppid = '[-0-9]*\s\(.*\)\s[A-Za-z]\s([0-9]*).*';
+
+sub generate_traceevent_regex {
+	my $event = shift;
+	my $default = shift;
+	my $regex;
+
+	# Read the event format or use the default
+	if (!open (FORMAT, "/sys/kernel/tracing/events/$event/format")) {
+		$regex = $default;
+	} else {
+		my $line;
+		while (!eof(FORMAT)) {
+			$line = <FORMAT>;
+			if ($line =~ /^print fmt:\s"(.*)",.*/) {
+				$regex = $1;
+				$regex =~ s/%p/\([0-9a-f]*\)/g;
+				$regex =~ s/%d/\([-0-9]*\)/g;
+				$regex =~ s/%lu/\([0-9]*\)/g;
+			}
+		}
+	}
+
+	# Verify fields are in the right order
+	my $tuple;
+	foreach $tuple (split /\s/, $regex) {
+		my ($key, $value) = split(/=/, $tuple);
+		my $expected = shift;
+		if ($key ne $expected) {
+			print("WARNING: Format not as expected '$key' != '$expected'");
+			$regex =~ s/$key=\((.*)\)/$key=$1/;
+		}
+	}
+
+	if (defined shift) {
+		die("Fewer fields than expected in format");
+	}
+
+	return $regex;
+}
+$regex_fragdetails = generate_traceevent_regex("kmem/mm_page_alloc_extfrag",
+			$regex_fragdetails_default,
+			"page", "pfn",
+			"alloc_order", "fallback_order", "pageblock_order",
+			"alloc_migratetype", "fallback_migratetype",
+			"fragmenting", "change_ownership");
+
+sub read_statline($) {
+	my $pid = $_[0];
+	my $statline;
+
+	if (open(STAT, "/proc/$pid/stat")) {
+		$statline = <STAT>;
+		close(STAT);
+	}
+
+	if ($statline eq '') {
+		$statline = "-1 (UNKNOWN_PROCESS_NAME) R 0";
+	}
+
+	return $statline;
+}
+
+sub guess_process_pid($$) {
+	my $pid = $_[0];
+	my $statline = $_[1];
+
+	if ($pid == 0) {
+		return "swapper-0";
+	}
+
+	if ($statline !~ /$regex_statname/o) {
+		die("Failed to math stat line for process name :: $statline");
+	}
+	return "$1-$pid";
+}
+
+sub parent_info($$) {
+	my $pid = $_[0];
+	my $statline = $_[1];
+	my $ppid;
+
+	if ($pid == 0) {
+		return "NOPARENT-0";
+	}
+
+	if ($statline !~ /$regex_statppid/o) {
+		die("Failed to match stat line process ppid:: $statline");
+	}
+
+	# Read the ppid stat line
+	$ppid = $1;
+	return guess_process_pid($ppid, read_statline($ppid));
+}
+
+sub process_events {
+	my $traceevent;
+	my $process_pid;
+	my $cpus;
+	my $timestamp;
+	my $tracepoint;
+	my $details;
+	my $statline;
+
+	# Read each line of the event log
+EVENT_PROCESS:
+	while ($traceevent = <STDIN>) {
+		if ($traceevent =~ /$regex_traceevent/o) {
+			$process_pid = $1;
+			$tracepoint = $4;
+
+			if ($opt_read_procstat || $opt_prepend_parent) {
+				$process_pid =~ /(.*)-([0-9]*)$/;
+				my $process = $1;
+				my $pid = $2;
+
+				$statline = read_statline($pid);
+
+				if ($opt_read_procstat && $process eq '') {
+					$process_pid = guess_process_pid($pid, $statline);
+				}
+
+				if ($opt_prepend_parent) {
+					$process_pid = parent_info($pid, $statline) . " :: $process_pid";
+				}
+			}
+
+			# Unnecessary in this script. Uncomment if required
+			# $cpus = $2;
+			# $timestamp = $3;
+		} else {
+			next;
+		}
+
+		# Perl Switch() sucks majorly
+		if ($tracepoint eq "mm_page_alloc") {
+			$perprocesspid{$process_pid}->{MM_PAGE_ALLOC}++;
+		} elsif ($tracepoint eq "mm_page_free") {
+			$perprocesspid{$process_pid}->{MM_PAGE_FREE}++
+		} elsif ($tracepoint eq "mm_page_free_batched") {
+			$perprocesspid{$process_pid}->{MM_PAGE_FREE_BATCHED}++;
+		} elsif ($tracepoint eq "mm_page_pcpu_drain") {
+			$perprocesspid{$process_pid}->{MM_PAGE_PCPU_DRAIN}++;
+			$perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED}++;
+		} elsif ($tracepoint eq "mm_page_alloc_zone_locked") {
+			$perprocesspid{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED}++;
+			$perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED}++;
+		} elsif ($tracepoint eq "mm_page_alloc_extfrag") {
+
+			# Extract the details of the event now
+			$details = $5;
+
+			my ($page, $pfn);
+			my ($alloc_order, $fallback_order, $pageblock_order);
+			my ($alloc_migratetype, $fallback_migratetype);
+			my ($fragmenting, $change_ownership);
+
+			if ($details !~ /$regex_fragdetails/o) {
+				print "WARNING: Failed to parse mm_page_alloc_extfrag as expected\n";
+				next;
+			}
+
+			$perprocesspid{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG}++;
+			$page = $1;
+			$pfn = $2;
+			$alloc_order = $3;
+			$fallback_order = $4;
+			$pageblock_order = $5;
+			$alloc_migratetype = $6;
+			$fallback_migratetype = $7;
+			$fragmenting = $8;
+			$change_ownership = $9;
+
+			if ($fragmenting) {
+				$perprocesspid{$process_pid}->{HIGH_EXT_FRAG}++;
+				if ($fallback_order <= 3) {
+					$perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE}++;
+				} else {
+					$perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE}++;
+				}
+			}
+			if ($change_ownership) {
+				$perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED}++;
+			}
+		} else {
+			$perprocesspid{$process_pid}->{EVENT_UNKNOWN}++;
+		}
+
+		# Catch a full pcpu drain event
+		if ($perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED} &&
+				$tracepoint ne "mm_page_pcpu_drain") {
+
+			$perprocesspid{$process_pid}->{HIGH_PCPU_DRAINS}++;
+			$perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED} = 0;
+		}
+
+		# Catch a full pcpu refill event
+		if ($perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED} &&
+				$tracepoint ne "mm_page_alloc_zone_locked") {
+			$perprocesspid{$process_pid}->{HIGH_PCPU_REFILLS}++;
+			$perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED} = 0;
+		}
+
+		if ($sigint_pending) {
+			last EVENT_PROCESS;
+		}
+	}
+}
+
+sub dump_stats {
+	my $hashref = shift;
+	my %stats = %$hashref;
+
+	# Dump per-process stats
+	my $process_pid;
+	my $max_strlen = 0;
+
+	# Get the maximum process name
+	foreach $process_pid (keys %perprocesspid) {
+		my $len = length($process_pid);
+		if ($len > $max_strlen) {
+			$max_strlen = $len;
+		}
+	}
+	$max_strlen += 2;
+
+	printf("\n");
+	printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+		"Process", "Pages",  "Pages",      "Pages", "Pages", "PCPU",  "PCPU",   "PCPU",    "Fragment",  "Fragment", "MigType", "Fragment", "Fragment", "Unknown");
+	printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+		"details", "allocd", "allocd",     "freed", "freed", "pages", "drains", "refills", "Fallback", "Causing",   "Changed", "Severe", "Moderate", "");
+
+	printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+		"",        "",       "under lock", "direct", "pagevec", "drain", "", "", "", "", "", "", "", "");
+
+	foreach $process_pid (keys %stats) {
+		# Dump final aggregates
+		if ($stats{$process_pid}->{STATE_PCPU_PAGES_DRAINED}) {
+			$stats{$process_pid}->{HIGH_PCPU_DRAINS}++;
+			$stats{$process_pid}->{STATE_PCPU_PAGES_DRAINED} = 0;
+		}
+		if ($stats{$process_pid}->{STATE_PCPU_PAGES_REFILLED}) {
+			$stats{$process_pid}->{HIGH_PCPU_REFILLS}++;
+			$stats{$process_pid}->{STATE_PCPU_PAGES_REFILLED} = 0;
+		}
+
+		printf("%-" . $max_strlen . "s %8d %10d   %8d %8d   %8d %8d %8d   %8d %8d %8d %8d %8d %8d\n",
+			$process_pid,
+			$stats{$process_pid}->{MM_PAGE_ALLOC},
+			$stats{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED},
+			$stats{$process_pid}->{MM_PAGE_FREE},
+			$stats{$process_pid}->{MM_PAGE_FREE_BATCHED},
+			$stats{$process_pid}->{MM_PAGE_PCPU_DRAIN},
+			$stats{$process_pid}->{HIGH_PCPU_DRAINS},
+			$stats{$process_pid}->{HIGH_PCPU_REFILLS},
+			$stats{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG},
+			$stats{$process_pid}->{HIGH_EXT_FRAG},
+			$stats{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED},
+			$stats{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE},
+			$stats{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE},
+			$stats{$process_pid}->{EVENT_UNKNOWN});
+	}
+}
+
+sub aggregate_perprocesspid() {
+	my $process_pid;
+	my $process;
+	undef %perprocess;
+
+	foreach $process_pid (keys %perprocesspid) {
+		$process = $process_pid;
+		$process =~ s/-([0-9])*$//;
+		if ($process eq '') {
+			$process = "NO_PROCESS_NAME";
+		}
+
+		$perprocess{$process}->{MM_PAGE_ALLOC} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC};
+		$perprocess{$process}->{MM_PAGE_ALLOC_ZONE_LOCKED} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED};
+		$perprocess{$process}->{MM_PAGE_FREE} += $perprocesspid{$process_pid}->{MM_PAGE_FREE};
+		$perprocess{$process}->{MM_PAGE_FREE_BATCHED} += $perprocesspid{$process_pid}->{MM_PAGE_FREE_BATCHED};
+		$perprocess{$process}->{MM_PAGE_PCPU_DRAIN} += $perprocesspid{$process_pid}->{MM_PAGE_PCPU_DRAIN};
+		$perprocess{$process}->{HIGH_PCPU_DRAINS} += $perprocesspid{$process_pid}->{HIGH_PCPU_DRAINS};
+		$perprocess{$process}->{HIGH_PCPU_REFILLS} += $perprocesspid{$process_pid}->{HIGH_PCPU_REFILLS};
+		$perprocess{$process}->{MM_PAGE_ALLOC_EXTFRAG} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG};
+		$perprocess{$process}->{HIGH_EXT_FRAG} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAG};
+		$perprocess{$process}->{HIGH_EXT_FRAGMENT_CHANGED} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED};
+		$perprocess{$process}->{HIGH_EXT_FRAGMENT_SEVERE} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE};
+		$perprocess{$process}->{HIGH_EXT_FRAGMENT_MODERATE} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE};
+		$perprocess{$process}->{EVENT_UNKNOWN} += $perprocesspid{$process_pid}->{EVENT_UNKNOWN};
+	}
+}
+
+sub report() {
+	if (!$opt_ignorepid) {
+		dump_stats(\%perprocesspid);
+	} else {
+		aggregate_perprocesspid();
+		dump_stats(\%perprocess);
+	}
+}
+
+# Process events or signals until neither is available
+sub signal_loop() {
+	my $sigint_processed;
+	do {
+		$sigint_processed = 0;
+		process_events();
+
+		# Handle pending signals if any
+		if ($sigint_pending) {
+			my $current_time = time;
+
+			if ($sigint_exit) {
+				print "Received exit signal\n";
+				$sigint_pending = 0;
+			}
+			if ($sigint_report) {
+				if ($current_time >= $sigint_received + 2) {
+					report();
+					$sigint_report = 0;
+					$sigint_pending = 0;
+					$sigint_processed = 1;
+				}
+			}
+		}
+	} while ($sigint_pending || $sigint_processed);
+}
+
+signal_loop();
+report();