kvm tools: Warn if guest RAM size exceeds host RAM size

Guest memory size that's larger than host physical RAM can cause swap deaths on
the host so warn the user about it.

Cc: Asias He <asias.hejun@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Suggested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index b9cdec27fd4b93cca689ca0455a5be4687725910..764a2427d330e4c4076803ac2d1fa8957c966fe6 100644 (file)
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -213,6 +213,18 @@ static void kernel_usage_with_options(void)
        fprintf(stderr, "\nPlease see 'kvm run --help' for more options.\n\n");
 }
 
+static u64 host_ram_size(void)
+{
+       long page_size;
+       long nr_pages;
+
+       nr_pages        = sysconf(_SC_PHYS_PAGES);
+
+       page_size       = sysconf(_SC_PAGE_SIZE);
+
+       return (nr_pages * page_size) >> MB_SHIFT;
+}
+
 /*
  * If user didn't specify how much memory it wants to allocate for the guest,
  * avoid filling the whole host RAM.
@@ -222,17 +234,11 @@ static void kernel_usage_with_options(void)
 static u64 get_ram_size(int nr_cpus)
 {
        long available;
-       long page_size;
-       long nr_pages;
        long ram_size;
 
        ram_size        = 64 * (nr_cpus + 3);
 
-       nr_pages        = sysconf(_SC_PHYS_PAGES);
-
-       page_size       = sysconf(_SC_PAGE_SIZE);
-
-       available       = ((nr_pages * page_size) >> MB_SHIFT) * RAM_SIZE_RATIO;
+       available       = host_ram_size() * RAM_SIZE_RATIO;
 
        if (ram_size > available)
                ram_size        = available;
@@ -364,6 +370,9 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
        if (ram_size < MIN_RAM_SIZE_MB)
                die("Not enough memory specified: %lluMB (min %lluMB)", ram_size, MIN_RAM_SIZE_MB);
 
+       if (ram_size > host_ram_size())
+               warning("Guest memory size %lluMB exceeds host physical RAM size %lluMB", ram_size, host_ram_size());
+
        ram_size <<= MB_SHIFT;
 
        if (!kvm_dev)