| Message ID | tip-f4abaa98c4575cc06ea5e1a593e3bc2c8de8ef48@git.kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [tip:x86/pti] x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off | expand |
* tip-bot for Michal Hocko <tipbot@zytor.com> wrote: > Commit-ID: f4abaa98c4575cc06ea5e1a593e3bc2c8de8ef48 > Gitweb: https://git.kernel.org/tip/f4abaa98c4575cc06ea5e1a593e3bc2c8de8ef48 > Author: Michal Hocko <mhocko@suse.com> > AuthorDate: Tue, 13 Nov 2018 19:49:10 +0100 > Committer: Thomas Gleixner <tglx@linutronix.de> > CommitDate: Mon, 10 Dec 2018 22:07:02 +0100 > > x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off > [ tglx: Folded the documentation delta change ] > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2095,6 +2095,9 @@ > off > Disables hypervisor mitigations and doesn't > emit any warnings. > + It also drops the swap size and available > + RAM limit restriction on both hypervisor and > + bare metal. > > Default is 'flush'. > > diff --git a/Documentation/admin-guide/l1tf.rst b/Documentation/admin-guide/l1tf.rst > index b85dd80510b0..2e65e6cb033e 100644 > --- a/Documentation/admin-guide/l1tf.rst > +++ b/Documentation/admin-guide/l1tf.rst > @@ -405,6 +405,9 @@ time with the option "l1tf=". The valid arguments for this option are: > > off Disables hypervisor mitigations and doesn't emit any > warnings. > + It also drops the swap size and available RAM limit restrictions > + on both hypervisor and bare metal. > + Note tha there's also some whitespace damage here: all other similar lines in this RST file start with two tabs, this one starts with 8 spaces. Thanks, Ingo
On Tue, 11 Dec 2018, Ingo Molnar wrote: > > off Disables hypervisor mitigations and doesn't emit any > > warnings. > > + It also drops the swap size and available RAM limit restrictions > > + on both hypervisor and bare metal. > > + > > Note tha there's also some whitespace damage here: all other similar > lines in this RST file start with two tabs, this one starts with 8 > spaces. Fixed...
On Tue 11-12-18 11:47:52, Thomas Gleixner wrote: > On Tue, 11 Dec 2018, Ingo Molnar wrote: > > > off Disables hypervisor mitigations and doesn't emit any > > > warnings. > > > + It also drops the swap size and available RAM limit restrictions > > > + on both hypervisor and bare metal. > > > + > > > > Note tha there's also some whitespace damage here: all other similar > > lines in this RST file start with two tabs, this one starts with 8 > > spaces. > > Fixed... Thanks Thomas! I haven't noticed a different whitespaces and relied on whatever vim decided to do.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 05a252e5178d..835e422572eb 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2095,6 +2095,9 @@ off Disables hypervisor mitigations and doesn't emit any warnings. + It also drops the swap size and available + RAM limit restriction on both hypervisor and + bare metal. Default is 'flush'. diff --git a/Documentation/admin-guide/l1tf.rst b/Documentation/admin-guide/l1tf.rst index b85dd80510b0..2e65e6cb033e 100644 --- a/Documentation/admin-guide/l1tf.rst +++ b/Documentation/admin-guide/l1tf.rst @@ -405,6 +405,9 @@ time with the option "l1tf=". The valid arguments for this option are: off Disables hypervisor mitigations and doesn't emit any warnings. + It also drops the swap size and available RAM limit restrictions + on both hypervisor and bare metal. + ============ ============================================================= The default is 'flush'. For details about L1D flushing see :ref:`l1d_flush`. @@ -576,7 +579,8 @@ Default mitigations The kernel default mitigations for vulnerable processors are: - PTE inversion to protect against malicious user space. This is done - unconditionally and cannot be controlled. + unconditionally and cannot be controlled. The swap storage is limited + to ~16TB. - L1D conditional flushing on VMENTER when EPT is enabled for a guest. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index a68b32cb845a..58689ac64440 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1002,7 +1002,8 @@ static void __init l1tf_select_mitigation(void) #endif half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT; - if (e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) { + if (l1tf_mitigation != L1TF_MITIGATION_OFF && + e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) { pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n"); pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n", half_pa); diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index ef99f3892e1f..427a955a2cf2 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -931,7 +931,7 @@ unsigned long max_swapfile_size(void) pages = generic_max_swapfile_size(); - if (boot_cpu_has_bug(X86_BUG_L1TF)) { + if (boot_cpu_has_bug(X86_BUG_L1TF) && l1tf_mitigation != L1TF_MITIGATION_OFF) { /* Limit the swap file size to MAX_PA/2 for L1TF workaround */ unsigned long long l1tf_limit = l1tf_pfn_limit(); /*
Commit-ID: f4abaa98c4575cc06ea5e1a593e3bc2c8de8ef48 Gitweb: https://git.kernel.org/tip/f4abaa98c4575cc06ea5e1a593e3bc2c8de8ef48 Author: Michal Hocko <mhocko@suse.com> AuthorDate: Tue, 13 Nov 2018 19:49:10 +0100 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Mon, 10 Dec 2018 22:07:02 +0100 x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off Swap storage is restricted to max_swapfile_size (~16TB on x86_64) whenever the system is deemed affected by L1TF vulnerability. Even though the limit is quite high for most deployments it seems to be too restrictive for deployments which are willing to live with the mitigation disabled. We have a customer to deploy 8x 6,4TB PCIe/NVMe SSD swap devices which is clearly out of the limit. Drop the swap restriction when l1tf=off is specified. It also doesn't make much sense to warn about too much memory for the l1tf mitigation when it is forcefully disabled by the administrator. [ tglx: Folded the documentation delta change ] Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> Acked-by: Jiri Kosina <jkosina@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Borislav Petkov <bp@suse.de> Cc: <linux-mm@kvack.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181113184910.26697-1-mhocko@kernel.org --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ Documentation/admin-guide/l1tf.rst | 6 +++++- arch/x86/kernel/cpu/bugs.c | 3 ++- arch/x86/mm/init.c | 2 +- 4 files changed, 11 insertions(+), 3 deletions(-)