Messages in this thread | | | Subject | Re: [PATCH v8 2/2] x86/mm: Don't disable PCID if the kernel is running on a hypervisor | From | Xi Ruoyao <> | Date | Wed, 17 Apr 2024 16:01:55 +0800 |
| |
On Tue, 2024-04-16 at 16:49 -0700, Sean Christopherson wrote: > On Sat, Apr 13, 2024, Xi Ruoyao wrote: > > The Intel erratum for "incomplete Global INVLPG flushes" says: > > > > This erratum does not apply in VMX non-root operation. It applies > > only when PCIDs are enabled and either in VMX root operation or > > outside VMX operation. > > > > So if the kernel is running in a hypervisor, we are in VMX non-root > > operation and we should be safe to use PCID. > > > > Cc: Dave Hansen <dave.hansen@linux.intel.com> > > Cc: Michael Kelley <mhklinux@outlook.com> > > Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> > > Cc: Sean Christopherson <seanjc@google.com> > > Cc: Andrew Cooper <andrew.cooper3@citrix.com> > > Link: https://lore.kernel.org/all/168436059559.404.13934972543631851306tip-bot2@tip-bot2/ > > Link: https://cdrdv2.intel.com/v1/dl/getContent/740518 # RPL042, rev. 13 > > Link: https://cdrdv2.intel.com/v1/dl/getContent/682436 # ADL063, rev. 24 > > Signed-off-by: Xi Ruoyao <xry111@xry111.site> > > --- > > arch/x86/mm/init.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > > index c318cdc35467..6010f86c5acd 100644 > > --- a/arch/x86/mm/init.c > > +++ b/arch/x86/mm/init.c > > @@ -275,6 +275,14 @@ static void __init probe_page_size_mask(void) > > * microcode is not updated to fix the issue. > > */ > > static const struct x86_cpu_id invlpg_miss_ids[] = { > > + /* Only bare-metal is affected. PCIDs in guests are OK. */ > > + { > > + .vendor = X86_VENDOR_INTEL, > > + .family = 6, > > + .model = INTEL_FAM6_ANY, > > + .feature = X86_FEATURE_HYPERVISOR, > > Isn't this inverted? x86_match_cpu() will return NULL if the CPU doesn't have > HYPERVISOR. We want it to return NULL if the CPU *does* have HYPERVISOR.
Hmm, but it seems not possible to let x86_match_cpu() to always return NULL if the CPU does have HYPERVISOR. If I read x86_match_cpu() correctly it cannot do an inverted feature match. Or am I misunderstanding something here?
Instead this makes x86_match_cpu() return an entry with driver_data = 0 if the CPU have HYPERVISOR, thus boot_cpu_data.microcode < invlpg_miss_match->driver_data will always be false when the CPU have HYPERVISOR and PCID won't be disabled.
> > + .driver_data = 0, > > + }, > > INTEL_MATCH(INTEL_FAM6_ALDERLAKE, 0x2e), > > INTEL_MATCH(INTEL_FAM6_ALDERLAKE_L, 0x42c), > > INTEL_MATCH(INTEL_FAM6_ATOM_GRACEMONT, 0x11), > > -- > > 2.44.0 > >
-- Xi Ruoyao <xry111@xry111.site> School of Aerospace Science and Technology, Xidian University
| |