Patch "KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-selftests-make-sure-kvm_create_max_vcpus-test-wo.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0961c952dd3bf0193cffcadfc1dd56670a98309a
Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Date:   Tue Nov 23 14:59:53 2021 +0100

    KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
    
    [ Upstream commit 908fa88e420f30dde6d80f092795a18ec72ca6d3 ]
    
    With the elevated 'KVM_CAP_MAX_VCPUS' value kvm_create_max_vcpus test
    may hit RLIMIT_NOFILE limits:
    
     # ./kvm_create_max_vcpus
     KVM_CAP_MAX_VCPU_ID: 4096
     KVM_CAP_MAX_VCPUS: 1024
     Testing creating 1024 vCPUs, with IDs 0...1023.
     /dev/kvm not available (errno: 24), skipping test
    
    Adjust RLIMIT_NOFILE limits to make sure KVM_CAP_MAX_VCPUS fds can be
    opened. Note, raising hard limit ('rlim_max') requires CAP_SYS_RESOURCE
    capability which is generally not needed to run kvm selftests (but without
    raising the limit the test is doomed to fail anyway).
    
    Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
    Message-Id: <20211123135953.667434-1-vkuznets@xxxxxxxxxx>
    [Skip the test if the hard limit can be raised. - Paolo]
    Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Tested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
index 0299cd81b8ba2..aa3795cd7bd3d 100644
--- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
+++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
@@ -12,6 +12,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/resource.h>
 
 #include "test_util.h"
 
@@ -40,10 +41,39 @@ int main(int argc, char *argv[])
 {
 	int kvm_max_vcpu_id = kvm_check_cap(KVM_CAP_MAX_VCPU_ID);
 	int kvm_max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
+	/*
+	 * Number of file descriptors reqired, KVM_CAP_MAX_VCPUS for vCPU fds +
+	 * an arbitrary number for everything else.
+	 */
+	int nr_fds_wanted = kvm_max_vcpus + 100;
+	struct rlimit rl;
 
 	pr_info("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
 	pr_info("KVM_CAP_MAX_VCPUS: %d\n", kvm_max_vcpus);
 
+	/*
+	 * Check that we're allowed to open nr_fds_wanted file descriptors and
+	 * try raising the limits if needed.
+	 */
+	TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl), "getrlimit() failed!");
+
+	if (rl.rlim_cur < nr_fds_wanted) {
+		rl.rlim_cur = nr_fds_wanted;
+		if (rl.rlim_max < nr_fds_wanted) {
+			int old_rlim_max = rl.rlim_max;
+			rl.rlim_max = nr_fds_wanted;
+
+			int r = setrlimit(RLIMIT_NOFILE, &rl);
+			if (r < 0) {
+				printf("RLIMIT_NOFILE hard limit is too low (%d, wanted %d)\n",
+				       old_rlim_max, nr_fds_wanted);
+				exit(KSFT_SKIP);
+			}
+		} else {
+			TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
+		}
+	}
+
 	/*
 	 * Upstream KVM prior to 4.8 does not support KVM_CAP_MAX_VCPU_ID.
 	 * Userspace is supposed to use KVM_CAP_MAX_VCPUS as the maximum ID